47-55.1 Any AC experts?

[TX3100Guy]

While this issue was not with my Chevy truck, I suspect there are multiple AC experts here and hope you guys can offer some useful suggestions on what I should do next.

I have a Classic Air AC system installed on another old classic car. It was blowing cold for a minute or two and then blowing hot. Last week while taking it to a car show, it blew cold for five to ten minutes, then it shut itself off (literally stopped blowing all together). Since it was nearly 100 degree's the wife and I opened the windows for some hot breeze. Maybe another ten minutes later I tried turning it back on (I had turned it off when it stopped on its own). It would only blow hot air.

A friend/mechanic suggested that I had a bad expansion valve, so I purchased a replacement and pulled the evaporator coil/fan unit out of the car and replaced the expansion valve. I then used my vacuum pump to draw a vacuum for over an hour, shut the manifold valves, let it sit for several hours with no loss of vacuum. I then ran the vacuum for another hour before I began adding R134a with the car and AC running. Shortly after allowing the refrigerant to enter via the low pressure side the compressor clutch engaged and I thought things were going well. Then I noticed that the R123a can was icing up and the low side pressures were nearly 50 and the high side was barely 20-30. Then the evaporator fan shut off, the compressor clutch de-engaged and no R134a was entering the system.

I closed all the manifold and hi/lo valves. I had a suspicion that the binary switch was defective, but after removal and testing it appears to work properly (although I'm open to suggestions if this could be the culprit).

My current thought is that the expansion valve might not have been the problem at all. Couldn't it be that the compressor has issues and that when its blowing hot, it because the clutch has disengaged too soon? I can't explain why the system shuts off, unless the binary switch is sensing too high of pressures and is shutting things down. As you can see, I'm grasping at straws for a solution.

At the moment, I have evacuated the system yet again and have it sealed off under vacuum overnight to ensure there are no leaks. Any thoughts are appreciated.

[mr48chev]

AC is something that I know very little about. About all I ever did with it was when I worked afternoons for WH (Tommy) Thomas in Waco in the 70's and when I showed up for work after getting out of my college classes he would say "here, install this and then hook the vacuum pump up and turn it on and leave for lunch.

Personally, Since Classic AC is 35 miles from you I'd first contact them and give them the info you gave us and hope that they have a shop that they so service work in. Or can reccomend a shop that they trust, this is where name dropping counts big if they suggest a shop, you tell the shop manager that they sent you there.

[TX3100Guy]

Originally Posted by mr48chev

Personally, Since Classic AC is 35 miles from you I'd first contact them and give them the info you gave us and hope that they have a shop that they so service work in. Or can recommend a shop that they trust, this is where name dropping counts big if they suggest a shop, you tell the shop manager that they sent you there.

I spoke with Classic AC after I ordered the expansion valve and it was the incorrect size and they were borderline rude about it. I ended up getting it from Summit. I will attempt their tech support on Monday but I don't have high hopes.

[mr48chev]

Well that sucks. Outside of the actual product what keeps you in business is providing good service and tech support.

If you are selling ac units for older rigs or wiring kits for older rigs how you support those kits and systems after the sale means as much or more than the actual product does. That includes how your counter person communicates with a customer.

To me, if they knew you were 35 miles away that should have been a "bring it over and we will have the guys in the shop check it out" deal. Not as a free service unless it is a new unit and they find something that had a manufacturing defect but as much of a they want to know as anything else.

[chevyguyase]

If your expansion valve is stuck closed your low pressure side will be low because the compressor will be sucking on a closed valve. If it is stuck open there will be no division between the hi and low side so the pressures will be almost the same. You are saying "binary switch' which should be on the high side line or on the dryer. If you loose your Freon it will shut off your compressor because Freon transports the oil your compressor needs. It sounds like you have a trinary switch, which has 3 or more terminals. You may also have a pressure cycling switch. You say it "literally stopped blowing all together", does that mean evaporator blower too? If you can show a diagram of your ac control system that would help. If you have an electric cooling fan make sure it works. If it doesn't your high side will climb over 400 psi and safe guards will shut your compressor off..

[TX3100Guy]

Originally Posted by chevyguyase

If your expansion valve is stuck closed your low pressure side will be low because the compressor will be sucking on a closed valve. If it is stuck open there will be no division between the hi and low side so the pressures will be almost the same. You are saying "binary switch' which should be on the high side line or on the dryer. If you loose your Freon it will shut off your compressor because Freon transports the oil your compressor needs. It sounds like you have a trinary switch, which has 3 or more terminals. You may also have a pressure cycling switch. You say it "literally stopped blowing all together", does that mean evaporator blower too? If you can show a diagram of your ac control system that would help. If you have an electric cooling fan make sure it works. If it doesn't your high side will climb over 400 psi and safe guards will shut your compressor off..

Thank you for weighing in, here are the answers to your questions.

1) I called it a binary switch because that is what the replacement part on Classic Air called it. It only has two male spade terminals on the top of it.

2) Yes, the evaporator blower has stopped too. However, today, I disconnected it (electrically) from the car and used a bench 12 volt transformer to show that the fan works when attached to both positive and ground.

3) I do have an electric cooling fan on the radiator/condenser. It is wired to the car in such a way (via a Hayden relay switch) that when the AC fan is powered on, that fan automatically comes on. Shut the AC off and unless the radiator is over 180 degrees, the fan will turn off, if the car is over 180 degrees, the fan will continue to run.

4) The entire AC unit is only connected to the car with three wires. Ground, Battery power (inline fuse), and the signal wire that goes directly to the binary pressure switch. The wire on the other binary terminal then goes directly to the compressor. The Hayden relay for the electric cooling fan has its wire spliced into the wire coming from the binary switch to the compressor. When the compressor gets power, it signals the cooling fan to run.

This morning I noticed that overnight I had a slow leak in the vacuum, so I swapped out a couple of o-rings and re-tightened several connectors. I ran a successful vacuum and let it set for several hours with no leaks. I'm letting it sit overnight to ensure it is leak free before I attempt putting refrigerant in again.

PS. The binary switch is marked "Lo under 28 psi - OFF, over 400 PSI - OFF"

[joedoh]

i just noticed you replied to chevyguy, sounds like your inside unit is freezing up, if the scroll fan is stopping. this can happen with low charge and also with high charge. how did you charge the system?

also, if you are running the system in high humidity, there is no outside air function on most aftermarket air conditioning systems, that outside air heat is what keeps the small small small inside evaporator from freezing up.

Originally Posted by chevyguyase

If you have an electric cooling fan make sure it works. If it doesn't your high side will climb over 400 psi and safe guards will shut your compressor off..

double this.

if your cooling fan isnt set to come on when the ac is on, you will have this problem. if you dont have an electric fan, your rad and condenser need to be "nut to butt" as my RCPO used to say and you need to have a ducted fan on the motor pulling a lot of air through them.

ever had your house ac quit because the outside fan on the unit quit spinning? this is the same thing.

[chevyguyase]

Tx3100guy, I'll watch for your after recharge results. You do have a binary switch. It will turn your compressor on if the pressure is over 28 psi and under 400 psi. I haven't told you anything you don't know already. I can't wrap my mind around the evaporator fan stopping, unless you are losing the hot or ground supply to your a/c system. The safe guards should not turn off your Evap blower. Most evap blowers are also your defrost blower and are independent of the compressor controls. Funny thought, Tx is an abbreviation for Thermal expansion valve.

[TX3100Guy]

Originally Posted by joedoh

i just noticed you replied to chevyguy, sounds like your inside unit is freezing up, if the scroll fan is stopping. this can happen with low charge and also with high charge. how did you charge the system?

also, if you are running the system in high humidity, there is no outside air function on most aftermarket air conditioning systems, that outside air heat is what keeps the small small small inside evaporator from freezing up.

if your cooling fan isnt set to come on when the ac is on, you will have this problem. if you dont have an electric fan, your rad and condenser need to be "nut to butt" as my RCPO used to say and you need to have a ducted fan on the motor pulling a lot of air through them.

ever had your house ac quit because the outside fan on the unit quit spinning? this is the same thing.

Answers to your questions, along with questions of mine. Thanks.

1) I was charging the system with a set of manifold gauges in my AC controlled shop, the ambient was 75 with low humidity. Would this make a difference?

2) At the time I was charging the system, the inside units fan was running (air temp coming out was 75) and the electric radiator fan was running. The condenser is mounted on the front of the aluminum radiator and the electric fan on the inside, it is a puller fan. All three (condenser, radiator, electric fan) are nut to butt.

3) The part I am still confused about is why the inside fan on the evap unit keeps quitting. The radiator fan stopping I understand if the binary switch gets a Hi or Lo condition, but the evap fan should still be running.

In fact, yesterday I tested the inline fuse and replaced the wire from the fuse to my fuse block and yes the fuse in the fuse block is a high enough amp and was not blown. This system has been in this car for over seven years wired exactly this way. I tested the ground wire too and it seems to be just fine.

4) when my home AC unit has frozen up (typically due to low refrigerant) the fan inside the house continues to run albeit with nothing but hot air. That's why I'm confused about the evap fan stopping.

Originally Posted by chevyguyase

Tx3100guy, I'll watch for your after recharge results. You do have a binary switch. It will turn your compressor on if the pressure is over 28 psi and under 400 psi. I haven't told you anything you don't know already. I can't wrap my mind around the evaporator fan stopping, unless you are losing the hot or ground supply to your a/c system. The safe guards should not turn off your Evap blower. Most evap blowers are also your defrost blower and are independent of the compressor controls. Funny thought, Tx is an abbreviation for Thermal expansion valve.

Like you the fan issue has me scratching my head. I've tested both power and ground. Before I remounted the unit with the new expansion valve, I ran the fan on my bench with a 12 volt transformer. It is a three speed fan and it ran fine on low and medium. On its high setting, it was running but it remained at the medium speed. I didn't think much of the problem because in the past the medium speed was fast and noisy enough in a small two seat car.


My remaining questions are 1) should I be recharging the system outside in 95 degree temps or in the shop at 75 degree? 2) what in the world is causing the evap fan to stop? 3) When I had the internal unit apart to replace the expansion valve, the temp control know has a silver coil/temp probe that was inserted into the cooling vanes of the evap coil. Could it be bad, whould it cause any of these issues?

[TX3100Guy]

I think the mystery of the fan has been located and rectified. I pulled the unit out of the car and put it on my bench. With the 12 volt transformer I was able to get the fan to run but intermittently. Then I spotted this when I pulled the inline fuse connector out of the car too.



With the cracked case, the glass fuse was not making full contact with the connection on one end of the inline fuse. This has been replaced now.

The question still remains should I be recharging outside in the 90+ degree heat or can I recharge the system in a temperature controlled shop. At this point, it is a moot point since I have to establish a vacuum again.

[dsraven]

I would start with the fan issue. I would use a couple of T style push pins from the craft store or staples etc and insert them into the power and ground plugs ins of the motor supply from the back side, then attach some jumper wires to them so you can test the circuit under running conditions without damaging your wiring by stabbing into the wire. when the fan (either one) stops running check to see what the voltage is and then, if good in your mind but the fan is still stopped, connect something that runs on 12v to those jumper wires (a headlight or another fan motor, whatever you have that actually draws some amperage) and see if it works. it would be wired parallel to the motor so if the other 12v draw works then I would look hard at the motor. when you tested before were your fan motors connected? if your multimeter says you have battery power at the terminals when you test that doesn't mean the circuit will support amperage to run a motor, it could fail with a load. just like a loose battery terminal will say you have 12v but when you go to start the car it just clicks and everything shuts off.
when you initially charged the system did you draw a vacuum with a vacuum pump for extended period, like overnight? that is what draws any contaminants out of the system. water, drbris from the hose builder or inside the tubing etc. you may have a drop of moisture in the system that becomes ice and plugs your tx. are you able to see or feel the area where the tx is located? does it frost up there and then past that it is warm? did the system come with a spec on how much refrigerant and oil should be added?

[TX3100Guy]

Originally Posted by dsraven

I would start with the fan issue. I would use a couple of T style push pins from the craft store or staples etc and insert them into the power and ground plugs ins of the motor supply from the back side, then attach some jumper wires to them so you can test the circuit under running conditions without damaging your wiring by stabbing into the wire. when the fan (either one) stops running check to see what the voltage is and then, if good in your mind but the fan is still stopped, connect something that runs on 12v to those jumper wires (a headlight or another fan motor, whatever you have that actually draws some amperage) and see if it works. it would be wired parallel to the motor so if the other 12v draw works then I would look hard at the motor. when you tested before were your fan motors connected? if your multimeter says you have battery power at the terminals when you test that doesn't mean the circuit will support amperage to run a motor, it could fail with a load. just like a loose battery terminal will say you have 12v but when you go to start the car it just clicks and everything shuts off.
when you initially charged the system did you draw a vacuum with a vacuum pump for extended period, like overnight? that is what draws any contaminants out of the system. water, debris from the hose builder or inside the tubing etc. you may have a drop of moisture in the system that becomes ice and plugs your tx. are you able to see or feel the area where the tx is located? does it frost up there and then past that it is warm? did the system come with a spec on how much refrigerant and oil should be added?

We must have been posting at the same time. If you read the posting before yours, you'll see that I did trace down the electrical issue with the fan. IT now runs properly.

To answer your question about charging the system. Yes, I used a set of manifold gauges to pull a vacuum with a vacuum pump. Initially ran the vacuum for nearly two hours. Watched it over the next four hours, with no reduction of vacuum, I then ran it again for another hour before closing the valves on the manifold and checking for any signs of a leak overnight. This morning, there was no change in the vacuum, but I opened it all back up to remove the evaporator unit to fuss with the fan issue.

I'm now about to reinstall the evaporator and hoses (with new oiled o-rings) and run another vacuum on it today and see if it holds overnight. Should I be charging the system outside in hot temps or is inside my shop ok?

[dsraven]

nice find.
do you have glass fuses in the fusebox as well? if not, and running the ATO or ATC fuses I like to use these inlinw fuses for add on stuff that hasn't been run through the regular fuse box like normal. these ones have a little cover that seals off the fuse for marine use but that cover also has a screw hole to mount it out of the way of mechanical damage like what happened to the plastic one you had issues with. there are others without the cover or, if you are in a bind and just wanna get it going, you can use an ATO/ATC fuse with the crimp on connector to match the spade terminal on the fuse. then make sure to use shrink wrap that covers the metal parts or at least tape those so they can't short on anything.
if it was me I would work on the system/charge the system in the shop, like any A/C shop would do. when you drive past an A/C shop you don't typically see the boys outside working on cars. the air conditioned shop would have less ambient humidity so less chance of moisture in the system. the only issue would be getting the vehicle hot enough inside when testing. you could do all the work and vacuum testing inside. charge the system, then run it and see what it does. then when done test it outside and see what you get for pressures in the heat

https://m.littelfuse.com/products/fu...e-holders.aspx

[dsraven]

I am not normally a fan of the inline fuse but sometimes they are unavoidable without a bunch of time spent on wiring. those style of plastic fuse holders are the worst in my opinion. they always seem to lose a spring or have a bad connection to the fuse. finding a glass fuse can also be a problem in a small town on saturday late afternoon, lol.

[TX3100Guy]

Originally Posted by dsraven

I am not normally a fan of the inline fuse but sometimes they are unavoidable without a bunch of time spent on wiring. those style of plastic fuse holders are the worst in my opinion. they always seem to lose a spring or have a bad connection to the fuse. finding a glass fuse can also be a problem in a small town on saturday late afternoon, lol.

The car in question is a 1969 Jaguar E-Type (XKE) and the entire fuse panel is glass tube fuses. Lucky for me, I have several dozen of them in a variety of amps. The inline fuse was from a previous owner, to be honest I cut it out and wired the AC unit to directly to the same fuse block that the inline fuse was wired to. The inline fuse replacement would require that I removed the evaporator unit to replace the use. This way, all I need to do is remove two thumb screws drop the instrument panel and replace a blown fuse if necessary.

I ended up replacing all the wires from the evap unit to the car. New hot wire to the fuse block, new ground wire to the back of the instrument panel and new wire from the evap unit to the binary switch.

[dsraven]

Probably a good idea. Then you know what you have.

[TX3100Guy]

Originally Posted by dsraven

Probably a good idea. Then you know what you have.

The evaporator unit in question. About to be reinstalled. The blue tape is just to hold the wires until I connect them.

[mr48chev]

You did replace the fuse holder with an ATO ATC fuse holder? Around here I have been having a hard time finding the round fuses in the parts houses at times.

[chevyguyase]

If you are charging your A/C by weight the ambient temperature won't matter. It will affect the pressure reading on your gauges. Lower temps usually equal lower pressures. There are Ambient/pressure charts on line for your pressures. Use a chart for TX valve and r134a, both will affect your pressures. You mentioned ". "The Hayden relay for the electric cooling fan has its wire spliced into the wire coming from the binary switch to the compressor. When the compressor gets power, it signals the cooling fan to run". I would like it if you were to move the splice to the other wire on your binary switch. This would turn your fan on when A/C is requested and not just when the compressor is running. Did the bad fuse holder supply all of the power to your A/C or just the evap fan? I'm wondering if the fuse was your only problem to begin with?

[TX3100Guy]

Originally Posted by mr48chev

You did replace the fuse holder with an ATO ATC fuse holder? Around here I have been having a hard time finding the round fuses in the parts houses at times.

I have one of those type fuses, but right now I just have the power line from the AC unit going directly to a glass fuse in the fuse block where formerly the inline fuse was connected.

[TX3100Guy]

Originally Posted by chevyguyase

If you are charging your A/C by weight the ambient temperature won't matter. It will affect the pressure reading on your gauges. Lower temps usually equal lower pressures. There are Ambient/pressure charts on line for your pressures. Use a chart for TX valve and r134a, both will affect your pressures. You mentioned ". "The Hayden relay for the electric cooling fan has its wire spliced into the wire coming from the binary switch to the compressor. When the compressor gets power, it signals the cooling fan to run". I would like it if you were to move the splice to the other wire on your binary switch. This would turn your fan on when A/C is requested and not just when the compressor is running. Did the bad fuse holder supply all of the power to your A/C or just the evap fan? I'm wondering if the fuse was your only problem to begin with?

I am recharging by weight, so that way I can stay in the temp controlled shop instead of outside in the Texas heat. Because the binary switch is always on, except when the pressure is too high or two low, the electric fan powers on as soon as the AC system is turned on. When the AC system is powered off, the Hayden relays temperature probe inserted in the upper part of the radiator determines if the fan should run. Over 180 degrees, it runs. Under 180 degrees it shuts off.

The fused line powers the fan for sure and during my testing, when it is powered on, the third wire to the binary switch is energized, so assuming there is no low pressure or high pressure issue, then the binary switch sends the 12 volt power to the compressor to engage the clutch.

[TX3100Guy]

As a follow-up, the short version of the story is that I had to replace the evaporator coil since the threads on the copper pipe fitting were stripped. After convincing Classic Air to sell it to me (since I wasn't the original owner/installer of the system, they required proof of ownership, which fortunately several photos of the unit sufficed), I installed the evap unit and reinstalled the unit in the car.

After a successful overnight vacuum on the system, I proceeded to charge the system by weight of the cans on a postal scale. The part that seemed strange to me was that once the refrigerant began entering the low side port (high side closed), I immediately saw an increase on the low side and slow but steady increase on the high side. However, the low side needle moved slowly and deliberately as the charge was entering, but the high side needle was wiggling wildly +/- 10 psi. It moved up from zero to 150 +/- 10 psi and the car was blowing cold. Not frigid, just cold - colder than ever in the past.

Once I had entered the amount of refrigerant that is called for (24 ounces) the gauges were about 29 psi - low side and 150 psi +/- on the high side. Mind you I was in a 75 degree garage, but with the garage door open since the car was running (nearly 100 outside in Dallas).

Is it normal for the high side gauge to be bouncing around while building pressure or is the compressor showing signs of a problem?

[chevyguyase]

I think you are doing good. Your pressures are good. As far as the fluctuation most conversions use axial/rotary compressors they come in 5 cyl. and 7 cyl. naturally the 7 cylinders have smoother pressure build up.Some gauges are dampened to make the needle steady some are not. If it wasn't cooling it would be something to be concerned with. You haven't mentioned refrigerant oil, but as deep as you go in to A/C repair, I'm sure sure you know about that. I think you're good to go. Can you tell us what you think was the cause and cure. Nice work.

[TX3100Guy]

Originally Posted by chevyguyase

I think you are doing good. Your pressures are good. As far as the fluctuation most conversions use axial/rotary compressors they come in 5 cyl. and 7 cyl. naturally the 7 cylinders have smoother pressure build up.Some gauges are dampened to make the needle steady some are not. If it wasn't cooling it would be something to be concerned with. You haven't mentioned refrigerant oil, but as deep as you go in to A/C repair, I'm sure sure you know about that. I think you're good to go. Can you tell us what you think was the cause and cure. Nice work.

I did add a small can of PAG oil with dye for future use, if necessary. Other than some self-created issues (see stripped threads on evap coil). The issue seems to have been caused by the bad expansion valve. At least, that's what I'm thinking for now.

Previously, the unit would blow cool for five minutes then blow hot air. This issue with the evap fan shutting down completely seems to have been a two-fold issue. First, was the bad inline fuse that had a crack in the case, and a mighty small cheap contact on one end that in conjunction with the crack in the case caused an intermittent power connection. Today, I realized that the glass fuse was wired to was too low of an amp rating (as an aside did you know there there is a difference in amp rating on glass fuses from the UK versus the US?) I had a US rated fuse in the block and not a UK one and blew it when the compressor ran for a minute or two and then my electric fan kicked in. Upon replacing the fuse with the correct amp (35 UK) everything worked as expected.

I took the car out for a 20 minute local drive and had cool air the whole way. Even the factory units in these old cars made the car comfortable but not "cold" given that there were created in the UK for the UK and certainly not Texas in the summer.

I will keep my fingers crossed that all is well going forward. Just as I was about to put the gauges away my son called me to tell me that his 2012 Hyundai Tucson has started blowing hot air........seems I have another customer....LOL

[chevyguyase]

Thanks for the follow up. I didn't know that about UK fuses. I'm sure the Hyundai will be easy after what you have been through.