Aircon compressor not kicking on?

[boybach]

My aircon (R134a converted system running R152a) wasn't working too good (68 at the vents) so today I thought I'd add some gas. Hooked up the manifold set and started adding a few cans of gas. Pressures were really low when I started and rose as I added the gas but never heard the compressor clutch engage or saw the pressures vary, so presume compressor isn't engaging.

Any ideas where to start checking system operation?

TIA

Larry

 

[pvfjr]

How high did the pressures get? Can you confirm that the low pressure switch was triggered with an ohmmeter? Also check for voltage on the green wire at the pressure switch. You should get battery voltage on green if AC is "turned on". You should then get battery voltage on black if pressure is high enough.

 

[pvfjr]

 

[pvfjr]

If you're not getting batt voltage to the green side of the pressure switch, then you have something going on with the controls or the thermostatic switch further upstream. Let us know what you find and we can go from there.

 

[boybach]

I can't remember the exact pressures but certainly up as far a 12 oclock on both gauges before I quit charging. Not at coach ATM so can't do any tests. Will report back when I go out to coach storage.

Thanks.

I just called my buddy who lives near the coach and asked him to have a look at the switch on the discharge line and what's going on with the switch that's not hooked up. He reported back that there's another switch on the line about 4" away from the disconnected one. It has the green and black wiring, so maybe the PO installed a new pressure switch on the line and left the old (I guess defective) one in place?

Will drop by tomorrow and take a pic.

 

[boybach]

Here's the pic of the low pressure switch arrangement. Looks like the switch was replaced and the PO left the old one in place? Didn't have opportunity to check voltages yet. Will report back.

 

[boybach]

If you're not getting batt voltage to the green side of the pressure switch, then you have something going on with the controls or the thermostatic switch further upstream. Let us know what you find and we can go from there.

Had a chance to go try the dash AC again today. Following your advice, first I unplugged and re-plugged the pressure switch and using a test light, checked for power on the green line, 12v, OK.
Next I started the engine and moved the control from max AC to normal AC, also working the temp slider back and forth settling on coldest setting.
Moving back outside, checked the other line and the test light lit up. Just then I heard the engine note change and sounded like the compressor came on. I went to get a temperature gauge to see what was happening at the dash vents and as I went back into the coach my buddy told me the lines under the hood were getting cold and also the compressor was now cycling.
With the coach idling and the gauge probe in the vent (about 20c 68f ambient) the air did feel cold. The gauge was dropping, it went down to about 5c, around 40f so I guess it's working now.
Could it have been the controls that weren't working properly? Up til today, every time I've used the coach in hot weather I've always set it to Max AC and had no AC ....I'm not sure how the controls work but setting it to normal AC today, well, seemed to work fine.

Thanks for all the help

Larry

 

[Richard RV]

Had a chance to go try the dash AC again today. Following your advice, first I unplugged and re-plugged the pressure switch and using a test light, checked for power on the green line, 12v, OK.
Next I started the engine and moved the control from max AC to normal AC, also working the temp slider back and forth settling on coldest setting.
Moving back outside, checked the other line and the test light lit up. Just then I heard the engine note change and sounded like the compressor came on. I went to get a temperature gauge to see what was happening at the dash vents and as I went back into the coach my buddy told me the lines under the hood were getting cold and also the compressor was now cycling.
With the coach idling and the gauge probe in the vent (about 20c 68f ambient) the air did feel cold. The gauge was dropping, it went down to about 5c, around 40f so I guess it's working now.
Could it have been the controls that weren't working properly? Up til today, every time I've used the coach in hot weather I've always set it to Max AC and had no AC ....I'm not sure how the controls work but setting it to normal AC today, well, seemed to work fine.

Thanks for all the help

Larry

The vacuum tubing on the dash HVAC control body is (to me) surprisingly complex, and half a century old. The odds of there being something wrong back there are pretty good.

Yesterday I went looking for the GMCMI 2018 Tucson seminar on rebuilding the controls to send to you - that's when I discovered the broken GMCMI links.

Not sure if you have seen that presentation handout, but if not you should track it down. Maybe somebody here has a copy they could send you?

 

[boybach]

The vacuum tubing on the dash HVAC control body is (to me) surprisingly complex, and half a century old. The odds of there being something wrong back there are pretty good.

Yesterday I went looking for the GMCMI 2018 Tucson seminar on rebuilding the controls to send to you - that's when I discovered the broken GMCMI links.

Not sure if you have seen that presentation handout, but if not you should track it down. Maybe somebody here has a copy they could send you?

Thanks, appreciate it!

 

[pvfjr]

Glad you got it going, Larry. My guess is you probably exercised an iffy connection and made it work for now. It may rear its head again, so keep your test light handy just in case. If it doesn't, well, enjoy it.