A/c not building pressure

[Davidf]

Ok, this one has me stumped. I retrofitted my stock a/c system to a CCOT (orifice tube and accumulator) system when I did my ls swap. Started to charge the system with R-134a and after several cans, could not get any high side pressure, low side very low while filling and could see pressure only when shaking can while filling. Shut off compressor and saw maybe 75 psi equalization pressures. Turn on compressor and virtually not low or high side pressures…no cooling effect what so ever. 60oz later, I stopped. What gives?

[68Gold/white]

Not sure I am following your explanation correctly, but!
If compressor is running and high and low sides are equalized on the gauges, your compressor is bad.

[kwmech]

Bad compressor or something in the system is plugging things up. Did you actually install the orifice tube in right direction

[Davidf]

Yes, to orifice tube in correct direction. I believe the compressor is working as it pulled a vacuum on the low side. It does seem like there is no orifice tube at all and the refrigerant is just getting pushed around in the loop. Very strange to me.

[Custom 68]

Based on what I had read when I was working on mine it does seem like your compressor is bad. I don't know that pulling a vacuum will tell you anything about the pump. It just indicates you have a closed system and no leaks.

I am assuming you have confirmed your compressor is actually kicking in (on) when you turn it on. You better check that too and make sure the clutch is kicking it on. They wont depending on your pressures or wiring.
good luck

Also adding I don't know how you got the system to take any Freon if the compressor is not working. I jut charged mine and when the compressor was cycling it wouldn't take any more freon until it kicked on. Are you sure your gages are working? You are correct it does sound odd.

60 Oz will be way too much. you will be closer to half that.
Dave

[Davidf]

Originally Posted by Custom 68

Based on what I had read when I was working on mine it does seem like your compressor is bad. I don't know that pulling a vacuum will tell you anything about the pump. It just indicates you have a closed system and no leaks.

I am assuming you have confirmed your compressor is actually kicking in (on) when you turn it on. You better check that too and make sure the clutch is kicking it on. They wont depending on your pressures or wiring.
good luck

Also adding I don't know how you got the system to take any Freon if the compressor is not working. I jut charged mine and when the compressor was cycling it wouldn't take any more freon until it kicked on. Are you sure your gages are working? You are correct it does sound odd.

60 Oz will be way too much. you will be closer to half that.
Dave

I know right. Yes, the compressor clutch is engaged and pulling in the refrigerant, but doing nothing. The gauges work because when I stop the compressor, the gauges show equalized pressure of about 75 psi. Engage the compressor and pressures fall to near near zero or the low side goes into vacuum. I jumped the cycling switch to engage compressor. Time to reclaim, open connection where orifice tube resides and make sure it is sealing/seated correctly.

So weird. I was able to pull a vacuum when evacuating, so cannot be a large leak that is just venting the refrigerant. And, I could not find any leaks with my halogen leak detector. the compressor was fine when pulled from donor vehicle.

[Custom 68]

David, I had figured you had covered all the easy bases but figured sometimes those easy ones get me. I am at a loss too, I would think if things are plugged up you would get something go high when you turned things on. I just finished a similar swap on mine but I did use a new compressor.
Keep us posted now I am intrigued.
good luck.
Dave

[Davidf]

Wonder what would happen if I have the condenser plumbed backwards? That is HP gas coming off compressor piped to bottom of condenser. Will have to check that when I get home this evening.

[Davidf]

Update: ok, at ambient temps, system pressures equalized at 140psi. Engage compressor and high side stays at 140 and low side goes well into vacuum. Condenser plumbed correctly.

So, seems to me there is a complete blockage in evaporator or accumulator, both of which are new. I know condenser is not blocked because I flushed the old r12 mineral oil out of it.

Going to open it up and check each leg of system with compressed air. Including through orifice tube when in place.

Thinking more, since high side pressure stayed at 140, blockage could be between compressor and high side service port. But, I would think it would get pulled down with low side if that was the case.

Thoughts/suggestions?

Edit: not sure of any of the above. Cannot get compressor to engage now. Seems HP cutout switch is keeping +12v from reaching ECM. So confused. Will start from ground zero tomorrow. First, got to figure out why only 10v at original compressor clutch wire. Then tackle HP switch/compressor and blockage.

[RustyPile]

The clue to all this is the fact that high side pressure is not building.. This means either the compressor is bad or there is blockage on the suction side preventing freon from getting to the compressor.. The accumulator is on the suction side.. I've seen cases where when the caps were removed from the accumulator fitting, the rubber gasket stuck to the pipe.. The gasket was unnoticed and when the hose was fitted into place, the rubber gasket blocked the passage... Like I said: IF there is a blockage, it's on the suction side -- defective hose, freon not boiling off in the evaporator (highly unlikely), plugged accumulator.. My money is on a bad compressor...

[kwmech]

Originally Posted by Davidf

Wonder what would happen if I have the condenser plumbed backwards? That is HP gas coming off compressor piped to bottom of condenser. Will have to check that when I get home this evening.

Don't think that would have any effect at all

[Davidf]

Originally Posted by RustyPile

The clue to all this is the fact that high side pressure is not building.. This means either the compressor is bad or there is blockage on the suction side preventing freon from getting to the compressor.. The accumulator is on the suction side.. I've seen cases where when the caps were removed from the accumulator fitting, the rubber gasket stuck to the pipe.. The gasket was unnoticed and when the hose was fitted into place, the rubber gasket blocked the passage... Like I said: IF there is a blockage, it's on the suction side -- defective hose, freon not boiling off in the evaporator (highly unlikely), plugged accumulator.. My money is on a bad compressor...

Not discounting anything at this point. No blockage at service ports...I already checked that. The suction service port is just after the accumulator in hose that feeds low side of compressor. The high side service port is right before the orifice tube which is located at inlet of evaporator. I can add refrigerant all day long since the low side is basically zero pressure or vacuum. I must have a leak, because where is the refrigerant? Is it trapped between compressor and high side service port?

Dunno...ugh!

[Davidf]

Originally Posted by kwmech

Don't think that would have any effect at all

I don't know, but you want the hp gas to enter the top of the condenser so that as it sheds latent heat and condenses to a liquid, it collects at the bottom of the condenser and gets pushed to the orifice tube. Regardless it is plumbed as hp gas to top of condenser...normal.

I will probably end up pulling condenser and evaporator and have them pressure tested. Then check all hoses and lines for blockage. Maybe even pull compressor and have it checked out. Not sure what else to do. Can the new accumulator be plugged up?

[Wrenchbender Ret]

Check for a plastic plug in the outlets of those new parts. They are capped to seal them off from dirt & moisture. There may be one still in there.

[kwmech]

Originally Posted by Davidf

. Can the new accumulator be plugged up?

Not really, the only thing inside of it is a desicant bag, unless the the bag came apart some how and blew its contents through the system. Of course they are made in china now-a-days. With the gauges hooked up are you are showing pressure right? --just equalized? no real high side pressure and no low.

[tinman_local2]

I am leaning more towards a leak somewhere. Pull a vacuum on it down to 29-30" hg. Let it set overnight(valves closed at manifold). If you have lost any vacuum, you have a leak. A somewhat small leak will show up in a few hours. If you add some dye to the system leaks are easier to find. If you have put 5 cans in the system, that is about twice as much as it needs. Gotta be going somewhere. Leak detectors don't work great unless there is absolutely no air movement. Refrigerant blows away pretty easily.

[Davidf]

Yes, there is a leak somewhere as vacuum did bleed off after about 15 minutes. But, I wanted to fill to see if it worked and to help me find the leak. Then, my world was rocked. I'll figure this out.

Going to start by disassembling the entire system...

[tinman_local2]

If it's bleeding off within 15 minutes, that's a pretty substantial leak. I would start by replacing every o ring and metal washer. Then pull another vacuum and let it sit overnight.

[Custom 68]

Like I had mentioned I just finished mine. It is a 68 with factory air cab. I swapped in an ls motor 12 or more years ago and was never quite satisfied so I pulled the evaporator out and replaced it with one from an 87 Silverado it went right in. It appears you did the same thing. When I did the original swap I changed condenser so that was done. I also purchased a new compressor. I had new hoses cut on the ones that changed. After it is all sealed up pull the vacuum in the heat of the day for a minimum of 30 min this will make sure you have the moisture out. I let it sit overnight and the loss was minimal at most so I was good. I then ran the vacuum again to ensure the moisture was out.
I then filled it and got it cold. I have not driven it in the real heat like we have now with the humidity but I may be a bit low on the charge I am just going to watch it and see how it does. I would rather sneak up on the charge. I am having a hard time knowing if it is correct from what I understand my low pressure should be higher in this high heat meaning I need a bit more freon as my high side is staying good. I hope to get it right this time and have cold air.
good luck
Dave

[kwmech]

If you are losing pressure that fast you should just about be able to hear it. When I get my oil new I put the dye in the oil right away regardless. That way I've always got dye in the system no matter what I'm working on

[Bigdav160]

Update: ok, at ambient temps, system pressures equalized at 140psi. Engage compressor and high side stays at 140 and low side goes well into vacuum. Condenser plumbed correctly.

140 tells me it's significantly overcharge but you said you've been feeding it cans.

Going into a vacuum like that says it's restricted. Temp gun, flir camera, touching will probably find it.

[kwmech]

Originally Posted by Bigdav160

140 tells me it's significantly overcharge but you said you've been feeding it cans.

Going into a vacuum like that says it's restricted. Temp gun, flir camera, touching will probably find it.

He's indicated there is also a severe leak

[Davidf]

Ok, tell me where this thinking is wrong: checked pressures this evening and equalized to about 100 psi. Jumped cycling switch and compressor engaged for 2 secs or so. During those two seconds, high and low pressures dropped to 50psi or so before HP switch shut down compressor. So, hp switch is working and sees high pressure, but my gauges do not. So, I think there is a block between compressor and hp service port. Yes/no?

Compressor is pushing against a wall and shutting off. Gauges are on other side of blockage, so hp gauge is seeing same thing as LP gauge because it is pulling through the orifice tube.

Going to crack line between compressor and condenser to see if I find all my refrigerant.

[kwmech]

Post up some pictures of this. I did the same thing to my 69 with the cycling system and did not run into any issues like this. Maaaaybee a few pictures will help??

[Davidf]

Solved:

Custom made hose was plugged solid. Hose has hp service port and reduced from #8 to #6. All that custom work and assumption is welded/sweated/soldered closed. So, compressor was pumping against a blockage that was just ahead of the orifice tube. Explains why I could get 48 to 60 oz of refrigerant in system as it was stored in condenser. Pinhole opening in blockage would allow slow equalization of pressure. Probably explains slow vacuum loss when evacuating as vacuum would equalize across the blockage….maybe not as I was pulling vacuum from both sides of system…we’ll see. There was still tons of refrigerant in system after one week.

I’ll get a new hose made Monday and report back after I get everything recharged.