Classic Retrofit AC Install- Compressor not building pressure?
 

Hi Folks,

I purchased the full kit last year and am finally getting it installed by Rennsport in Sealy, Texas. Car is a 77 911 widebody with 3.2SS running PMO.

Kit consists of 2 condensers, the CR Alternator, compressor, etc.

Initially the system worked and we were getting cold air, but found a leak at the drier bottle (bottle defect).
Based on Alex at CR's recommendation, we got this one-
https://coldhose.com/products/universal-receiver-drier-6-male-o-ring-fittings?variant=35532296913056
Drier is confirmed to be working by the mechanics at Rennsport.

Otherwise all other components are what we ordered from you and are installed.

I've run putty, checked functions. Was able to turn on the compressor using Putty, condenser fans, etc.

Below are screen shots of the system when its running.

Here is the issue- What is happening is that I can hear the compressor run (its a weird pulsating sound?), but then will turn off. This can be seen under the DIAG- Comp I where the amps can be seen going up and then going down. It will cycle through this. Start- Stop- Start - Stop.

We have pressure gauges hooked up, what is really interesting is that there is zero movement of the gauges. I thought that there might be a blockage, but Warren said that if there was a blockage, then the pressures would build up as the Freon moves to the blockage. Its almost like the compressor isn't moving refrigerant. There is zero movement of the gauge, except over a bit of time, it climbs up, because its getting hot.

Has anyone experienced this with their system? I've emailed Alex, but thought I'd ask the collective in case someone else has experienced this issue.

INITIAL DIAG-
http://forums.pelicanparts.com/uploa...1665178476.JPG

CAR RUNNING, COMPRESSOR ON-
http://forums.pelicanparts.com/uploa...1665178476.JPG

DIAG- CAR RUNNING
http://forums.pelicanparts.com/uploa...1665178476.JPGhttp://forums.pelicanparts.com/uploa...1665178880.jpg

Ok so it was working fine, but leaking, and all that was done was the drier was replaced? I think the driers are uni directional. Could it have been installed backwards?

A new expansion valve worked for me!

My understanding is that they are unidirectional. Also the mechanic stated that if in fact the drier was, say, clogged, we would see the pressures build up on the gauge; here we see no movement at all.

Interesting! Nick, so you had the same problem? Do you mind sharing which expansion valve you got as a replacement? Thanks!

Hi, can’t remember the name but I bought it from our host. Did not cost a lot. As soon as I installed it and after vacuum check and refill, my AC pressure worked normal !!! I think over time the expansion valve can get plugged. Also, it was an easy install. You will need a weird black sticky tape to put on some areas of the valve.

I bet it will fix your problem.

Call pelican, tell them your car year and order the expansion valve.

Thanks Nick. So I'm assuming the CR kit expansion valve is different from the OEM expansion valve that would have originally supplied by the car, no? Are they backwards compatible?

Can you confirm if the condenser fan is running?

I don’t know, I just called pelican and ordered the valve. Not a complicated little thing. They will give you the correct one. Cake !! Try it! My ac did not work , pressure was wrong! Installed part and system worked normally.

Jonny, thanks! Great question.

I didn't confirm the fans were running (2 condensers, so assuming both would kick on with the FAN=1 prompt?). I'll have the mechanic confirm on Monday for us by running the prompt and physically confirming that each fan does kick on.

With that said, I remember hearing the compressor kicking on (that pulsating sound which coincided with the spike in amps on Putty). Is there a lag in the pressure building up? I'm zooming into the picture here with the amp readings for the compressor and fan.

I know that with a conventional compressor, pressure changes happen immediately when the compressor kicks on.

Thoughts?

COMPRESSOR AMP CHANGE-

http://forums.pelicanparts.com/uploa...1665321792.JPG

CONICIDING WITH COMPRESSOR AMP INCREASE, FAN TURNING ON AND THEN OFF (ASSUMING IT CAME ON, WILL PHYSICALLY CONFIRM..)

http://forums.pelicanparts.com/uploa...1665321792.JPG

Yes, the compressor is 'soft start' so it takes a little while to build pressure. The compressor current is proportional to the pressure so we use the current reading to run the condenser fans ( as you note FAN=1 indicates that the ECU is asking for fans to run).

If the fans don't run due to wiring errors, the condensers will heat up and the pressure will go higher. This in turn will switch the compressor off for safety.

When the system is running properly, the compressor will run continuously.

Ah! Good to know about soft start. I'll get the mechanic to rerun the FAN=1 prompt to confirm the fans are in fact running and will circle back on this post.

Thanks Jonny!

Jonny, to follow up, we ran the diagnostics again. Fan previously wasn't coming on because of a loose fuse, that got addressed, now FAN=1 does turn on both the condenser fans.
When i run CMP=5, the contactor does connect, but i don't hear that weird sound of the compressor running.
When the car is running, when the AC button is pressed, the fans kick on, i believe i also do hear the compressor kicking on, but there is no change in pressures, and the compressor does 'kick' off from looking at the amp values on the RUN file.

Attached is the RUN file.http://forums.pelicanparts.com/uploa...1665506473.JPG

Close up-

http://forums.pelicanparts.com/uploa...1665506567.JPG

Thoughts on next steps?
Thanks.

The current is rising faster than I would expect. Has it got too much refrigerant? What is the pressure at rest (e.g not running)?

Hi Johnny, here is a pic of the pressures at rest.

http://forums.pelicanparts.com/uploa...1665520736.jpg

Thoughts?

^ Pressures look ok.

I am starting to think faulty pump but double check your hose plumbing.

We have had a couple of bad pumps. Any 'clanky' noises from it on start up?

I don't hear any clanky, but it does make a sound as its running, its pretty quiet though.

I'll have the mechanic check the hoses for any kinks right away and come back to you..

Ok, check the fundamental hose layout/flow too. I'll send you a compressor test procedure by email - tomorrow as it's late here.

Thanks Jonny. Had the mechanic check all the lines for kinks, etc. All look good.
Look forward to your email to run the compressor test procedure.
Thanks.