Factory A/C System Woes

[kna4977]

I have assembled disassembled cleaned replaced repaired multiple parts in my factory A/C system, but I can't seem to get it to work right. I put it all back together today. I charged it, but the high side pressure continues to climb once the vehicle is up to normal temperature. I can keep high side pressures in the normal range if I continuously spray water on the condenser. If I don't spray water on the condenser, the high side pressures rise quickly and exponentially. I want it to look correct, but also cool like it should. What are my options? What should I do? Low side pressures are normal and within the range that they should be.

[Richard]

I think I already gave an answer to this in your other post before you decided to use the stock condenser. Not trying to give a smart a** answer here. Repeat my point, the stock condenser and type of mounting does not provide enough heat rejection for 134a. So you can improve airflow and it may improve some. If the cooling at highway speeds is acceptable to you. Just improving airflow at lower speeds is an option. Using a more efficient condenser and improving airflow across condenser at lower speeds would be best. Or as some see as the best option, source r12 and make the poa as original.

[Stocker]

Originally Posted by Richard

the stock condenser and type of mounting does not provide enough heat rejection for 134a. So you can improve airflow and it may improve some. If the cooling at highway speeds is acceptable to you. Just improving airflow at lower speeds is an option. Using a more efficient condenser and improving airflow across condenser at lower speeds would be best.

Apparently the guys who converted my A/C to R134a a few years ago knew about that. They suggested I add pusher fans to improve cooling. I did, and it helped.

[kna4977]

Originally Posted by Richard

I think I already gave an answer to this in your other post before you decided to use the stock condenser. Not trying to give a smart a** answer here. Repeat my point, the stock condenser and type of mounting does not provide enough heat rejection for 134a. So you can improve airflow and it may improve some. If the cooling at highway speeds is acceptable to you. Just improving airflow at lower speeds is an option. Using a more efficient condenser and improving airflow across condenser at lower speeds would be best. Or as some see as the best option, source r12 and make the poa as original.

System has ester oil now. If I go back to R12 what all would I need to do besides adjust the POA back to 30PSI?

[PbFut]

Just to add some additional information points. My system is 100% stock parts. POA recalibrated to 134 spec. I am using ZeroR refrigerant from Amazon. System was completely disassembled, and cleaned. Ducting and Refrigerant lines and components. If outside air temps are under 100 degrees, there is no issues at all. At about 100 degrees outside temp, while stopped at a light, I notice a slight increase in cab temp. Once moving again the cabin temp quickly lowers. Not to say I am uncomfortable in the cab, just that I can tell I am not cooling quite as well than when more air is going over the condenser. As outside air temps lower, I am using lower fan settings or it will get uncomfortably cold in the cab and there are no issues at stop lights.

[MikeB]

Originally Posted by PbFut

At about 100 degrees outside temp, while stopped at a light, I notice a slight increase in cab temp. Once moving again the cabin temp quickly lowers.

I have a similar issue with the 27 year old Vintage Air R134a system in my truck. I haven't measured the air temp at the center vent recently, but I'd guess it rises from around 40 deg to 50 or more at a long stop light.

It's not a major deal, but I'd like to fix it. Sounds like even a small pusher fan in front of the tube & fin condenser would do it. Or maybe a more modern stacked plate condenser???

Just remembered that I also have a very small oil leak at the compressor. Not enough to drip or throw oil on the underside of the hood, but I can wipe oil off the bottom of the compressor and a mounting bracket. So, the problem could be I'm a tiny bit low on refrigerant. New Sanden compressors don't cost to much, so maybe I can kill two birds...

[howzzzit]

Originally Posted by MikeB

I have a similar issue with the 27 year old Vintage Air R134a system in my truck. I haven't measured the air temp at the center vent recently, but I'd guess it rises from around 40 deg to 50 or more at a long stop light.

It's not a major deal, but I'd like to fix it. Sounds like even a small pusher fan in front of the tube & fin condenser would do it. Or maybe a more modern stacked plate condenser???

Just remembered that I also have a very small oil leak at the compressor. Not enough to drip or throw oil on the underside of the hood, but I can wipe oil off the bottom of the compressor and a mounting bracket. So, the problem could be I'm a tiny bit low on refrigerant. New Sanden compressors don't cost to much, so maybe I can kill two birds...

Mike as you probably already know if your leaking oil you're leaking refrigerant.

[howzzzit]

Originally Posted by kna4977

I have assembled disassembled cleaned replaced repaired multiple parts in my factory A/C system, but I can't seem to get it to work right. I put it all back together today. I charged it, but the high side pressure continues to climb once the vehicle is up to normal temperature. I can keep high side pressures in the normal range if I continuously spray water on the condenser. If I don't spray water on the condenser, the high side pressures rise quickly and exponentially. I want it to look correct, but also cool like it should. What are my options? What should I do? Low side pressures are normal and within the range that they should be.

Fan positioned correctly in shroud?

[kna4977]

Originally Posted by howzzzit

Fan positioned correctly in shroud?

Everything with the fan and shroud is spot on.

It's charged with 3.5 cans of R134a and 10 oz of ester oil. Original system took 3.25 lbs of R12, so it should theoretically take (3.25x0.9) - 0.25 = 2.675 lbs or 42.8 ounces of refrigerant, which is about 3.5 - 12oz cans.

The lines, evaporator, and condenser were flushed many times. The drier and compressor are new.

The A/C pressures are within the normal range according to the chart I have. Low side gets close to 50 and high side around 275 at 100 degrees ambient temp.

Vent temps however are in the 60s. The upper and lower evaporator tubes feel to be the same temperature. POV valve has been calibrated to 27 or so vs 30 and tests fine. Expansion valve tests fine.

Heater valve is new, but functions exactly the same as the one I replaced and the hose going into the heater core from the valve feels about the same temperature as the one coming out of it and going back into the radiator.

What am I missing? I can but really don't want to go back to R12 because I don't want to do over all the work I just did removing everything and taking the entire system apart flushing and reinstalling etc.

Also I can spray water on the condenser and the pressure drops dramatically, but the vent temps don't.

[Rick Bollinger]

Your heater hose is not hot is it? If it is that would explain your high pressure and temp. It means you either have a faulty or wrong vacuum valve in your cab controls or a bad vacuum line. Mine had a 2 position valve when it was suppose to have a 3. So I put on the newer style heater valve. At full temp you should be able to hold your hose at full operating temp and just be warm.

[kna4977]

Originally Posted by Rick Bollinger

Your heater hose is not hot is it? If it is that would explain your high pressure and temp. It means you either have a faulty or wrong vacuum valve in your cab controls or a bad vacuum line. Mine had a 2 position valve when it was suppose to have a 3. So I put on the newer style heater valve. At full temp you should be able to hold your hose at full operating temp and just be warm.

Not really hot but both hoses feel like they are the same temp.

Should the heater valve flow any coolant at all when the a/c is on at full cooling capacity?

Tired of dealing with this without any type of resolution. Not sure what to try next and not sure if going back to R12 will work. Seems like something else may be amiss. I've converted several systems over the years and never had this issue.

[Rick Bollinger]

No it should not flow any. But all 3 of your controls should be over to the left. Look in your cowl passenger side and confirm that that door is closed if you can. your vent door passenger side by your feet on the inside should open up when on. Automatically close when off.

[Richard]

Originally Posted by howzzzit

Fan positioned correctly in shroud?

The inadequate airflow through the condenser is not from the fan. The condenser is located a considerable distance from the face of the radiator with large gaps around it to the core support. Air will take the path of least resistance. Closing up that gap around the condenser would increase flow through it. Though that may work. I think not a good option as you are reducing the square inches of intake for the radiator. As a test. Stuff some foam into that opening around the condenser. Would bet a dollar that pressures will improve.

[PbFut]

Points to check. I can't be specific as I'm not confident in memory of detail. So you will need to verify few things. The lower slide handle controls a blend door in the air box. All the way left and no air passes through the heater core. If that door is missing or damaged hot air will blend. The water valve to the core only shuts off if the upper control lever is in the far left position on the 2 port control. Far left position will close the normally open water valve and open the inside air door. If upper control is moved slightly right the water valve will open to heat the core and you can blend the air with the lower lever for desired temp. The middle lever controls vents and also switch for compressor. If the ac lines are cold and evaporator not freezing, it sounds like the blend door is leaking. Even if core is hot, the blend door keeps the core out of the airflow when fully closed. Is the control cable adjusted correctly? I would confirm cold evaporator. Then start looking at the core and blend door.

[kna4977]

Originally Posted by PbFut

Points to check. I can't be specific as I'm not confident in memory of detail. So you will need to verify few things. The lower slide handle controls a blend door in the air box. All the way left and no air passes through the heater core. If that door is missing or damaged hot air will blend. The water valve to the core only shuts off if the upper control lever is in the far left position on the 2 port control. Far left position will close the normally open water valve and open the inside air door. If upper control is moved slightly right the water valve will open to heat the core and you can blend the air with the lower lever for desired temp. The middle lever controls vents and also switch for compressor. If the ac lines are cold and evaporator not freezing, it sounds like the blend door is leaking. Even if core is hot, the blend door keeps the core out of the airflow when fully closed. Is the control cable adjusted correctly? I would confirm cold evaporator. Then start looking at the core and blend door.

All levers are to the left. All the vacuum pods and those controls check and operate as they should. If it's a blend door issue that would make a lot of sense and I hope that's what it is. The heater valve is new and functions exactly like the one I replaced. It is obviously letting some coolant through in it's current operation. If it's not the blend door, then I think there may be a blockage somewhere. How can I best verify the blend door operation? The evaporator doesn't appear to be freezing and the lines are cold. It's dripping condensate.

[PbFut]

I damaged my heater core last week installing a header. So it’s all apart right now and I can take some pics.
The blend door is in the right side (closest to passenger fender) of ac housing. It closes a pass through passage through the firewall and into the heater core box in the cab. First pic is of the fire wall in the cab with the heater core and air box removed and door closed. It is the smaller passage. The Evaporator chamber is in the larger opening in the photo. In this position the lower lever in the cold position and all air flow from fan going to left part of the AC box by the engine and through the evaporator. Second pic is of the door open and forcing fan air into the heater core chamber inside the air box in the cab. Mid positions of the lower HVAC control lever causes the blend door to be partially open or closed blending air over both the core and evaporator to adjust air temp. If the adjustment of the cable is such that the door does not fully close or fully open, you will always get an air blend. The 3rd photo is the door lever on the AC box attached to the blend door in the closed or cold position. The 3rd control lever pulls on the control cable attached to this odd looking part on the top of the AC box when in cold position. You can adjust by loosening the screw holding the cable attachment and pushing or pulling on the cable. You want the door fully closed by feel. Tighten, then test control lever and see if it will go all the way to hot. The cable will have pushed the door all the way open closing off the evaporator passage and now you have full heat. So if you get movement adjusting cable, its an indication the door was not fully closed and you were getting some core heat or if coolant was locked off with the valve you were still getting a blend of unconditioned air since it was bypassing the evaporator chamber pass an unheated heater core. I hope this makes sense. The blend door has rubber on it. If the rubber is gone it will leak no matter what position it is in or how you try to adjust.

[Rick Bollinger]

If your making water then things are working. No water should be leaking by your heat valve. Blend door needs to seal completely If it's original it is most likely not and can almost guarantee if you haven't taken the evap coil plenum apart to clean dirt and junk is keeping it from sealing as well. Then there is the fresh air door. This is in the cowl behind the vacuum diaphragm on the passenger side. Same deal it should be closed when all controls are to the left. If it does not seal it will pull warm air from the outside as well. Then the door inside the cab. It will be open circulating the cool air back through the evap coil cooling the air more all the time. When I installed all new doors in my system I did have to trim up the rubber a little bit here and there because it would bind up. But my old stuff was dry and brittle and did not seal at all. Plus had a lot of small leaves and dirt in it as well.