AC troubleshooting

[eacyde]

I'm trying to get my A/C working and I am having some issues.

1. Pulled a vacuum and determined no leaks
2. Charged the system with 16oz of R134. Pressure was 70psi

3. Compressor clutch does not turn on. I verified power at the pressure switch by the coolant overflow. I then jumpered the connector and still nothing.

Am I missing something?
Can I override the system to make the compressor clutch engage?

Any help is appreciated.


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[rubydist]

you must not have actually got a vacuum pulled on it, because 16 oz of refrigerant will not get you 70 psi. that is your first problem.

if there is power at the compressor but it won't run, then either the gap is too large (most likely) or the compressor coil is shot. search here for a thread on how to remove a shim from the compressor clutch and do that, and let us know the result.

 

[eacyde]

you must not have actually got a vacuum pulled on it, because 16 oz of refrigerant will not get you 70 psi. that is your first problem.

if there is power at the compressor but it won't run, then either the gap is too large (most likely) or the compressor coil is shot. search here for a thread on how to remove a shim from the compressor clutch and do that, and let us know the result.

Thanks.

We pulled a vacuum to 28"Hg for a few beers, then attached the R134.

the 16 OZ is by weight and the gauges on the high & low side were @ 70psi

 

[rubydist]

well, maybe I remember it wrong, but iirc it takes more than 16 oz of refrigerant to get to that pressure.

in any case, if you have power at the compressor connector, you either have a clutch gap issue or a clutch coil issue.

 

[eacyde]

well, maybe I remember it wrong, but iirc it takes more than 16 oz of refrigerant to get to that pressure.

in any case, if you have power at the compressor connector, you either have a clutch gap issue or a clutch coil issue.

I tried to find a dedicated thread on the shim issue with no luck.
From what I have read:
1. Broom Stick trick - Hit the clutch and see if it engages. (Cross Fingers this is all it needs)
2. Remove a shim or 2 from the clutch to bring it closer to the coil.

I suspect #1 will work as the clutch has not engaged in many miles.

@rubydist just for my information, are the AC compressors the same from a 93ATX & 95MTX. I cant remember if I used the compressor from the 3.2 or the 3.0 when I swapped in the 3.2

 

[luigisho]

The flip side is that this usually limps it along for a time but it won't be long until the compressor will likely be needing a replacement. That's just anecdotal from what I have observed from people posting here over the last 15+ years. There are those who managed to retain and operate the original 25yr old unit but that is not the norm. So short term play with the shim, if you have a (realistic) long term outlook in owning this car and budget wiggle room to do so, then I would look at replacement either now or somewhere in the next year or 2 given your location/need for ac.

 

[eacyde]

The flip side is that this usually limps it along for a time but it won't be long until the compressor will likely be needing a replacement. That's just anecdotal from what I have observed from people posting here over the last 15+ years. There are those who managed to retain and operate the original 25yr old unit but that is not the norm. So short term play with the shim, if you have a (realistic) long term outlook in owning this car and budget wiggle room to do so, then I would look at replacement either now or somewhere in the next year or 2 given your location/need for ac.

@luigisho
I have managed just fine for the last 4 years with out A/C. I am just a ***** now and like to have luxurious options. That being said, what is the best option for replacement? I have 2 spare compressors from previously stripped SHO's If they can be rebuilt and they are all the same (SHO speaking) then it shouldnt be too bad. Just a PITA to swap out.

 

[rubydist]

iirc, they are all the same.

I have removed shim and had it last for years. worry about replacement when needed.

 

[eacyde]

I tried the "broomstick" method and nothing.

When I charged the system with R134. Both the high pressure valve and low pressure valve were open.
Both sides are at 70psi. Could the high pressure switch be fooled into cutting out the clutch?

I'm not sure what the high side pressure should be or what the high pressure switch is set at.


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[rubydist]

no, the high pressure cutoff is much much higher than that. a couple hundred at least. but the switch could be bad, as could the low pressure switch. you can jumper them for a test. the high pressure switch has 4 terminals, iirc, and you need to jumper the correct 2 of them.

 

[eacyde]

no, the high pressure cutoff is much much higher than that. a couple hundred at least. but the switch could be bad, as could the low pressure switch. you can jumper them for a test. the high pressure switch has 4 terminals, iirc, and you need to jumper the correct 2 of them.

Do you know where the switch is located? I know there is a 2 pin switch just next to the overflow but I am unsure where the other switch is.

 

[rubydist]

the low pressure cycling switch is on top of the dryer.

the high pressure switch is on the high pressure line not too far behind the radiator.