A/C Recharge - Maxed Out Pressure Gage on DIY Can
 

Hello,

My A/C has not been working for a while now. The compressor is not engaging. I suspected that the reason was because the system was critically low on refrigerant. So, I went to the local auto parts store and purchased a can of R134a with a pressure gage. When I hooked up the can to the low pressure port, the the gage went completely around from zero and maxed out well above the maximum gauge pressure of 80 psi.

What does this mean? Is there a bad valve somewhere? Clearly the system is not low on refrigerant. Is fixing this problem a DIY job?

Thanks,

Mike

If the compressor is not engaging, the existing refrigerant will reach a static pressure approx. equal to air temp in degF. You can't charge unless compressor engages. That appears to be what you have encountered.

Since you have enough pressure to cause compressor to engage (if everything is working), there must be an electrical fault preventing compressor engagment.

The possibilities roughly in order of liklihood are 1) ac compressor clutch gap too large and clutch coil can close clutch 2) AC compressor relay has failed. 3) clutch coil has failed open 4) ac pressure switch which enable compressor has failed open, 5) AC thermostat has failed open.

Suggest checking for 12V at the compressor electrical connector when AC is commanded on (keyswitch On, fan on, AC switch On). If you have 12V, then clutch gap or clutch coil is the problem. If you don't have 12V, then ac compressor relay, ac pressure switch, or ac thermostat is possible.

I'm assuming the heater blower works.

good luck

In the future, please do not blindly add R-134a without doing some diagnostic work. Overcharging an a/c system is dangerous.

Also, start the engine cold and turn on the a/c. Do both fans on the radiator turn on?

1) I did not actually add R-134a. When I hooked up the can and found that the pressure was high, I figured that it would not be a good idea to add more.

2) Where is the fuse located and where are the relays? The second radiator fan turns on, but the compressor does not.

Thank you!

Do you have a volt meter? As suggested I would check to see if you are getting power to the compressor clutch first.

Anyway - for the compressor clutch there are two fuses that I would check. Underdash #30 - 7.5 amp.....this powers many other things so pretty sure it would be ok since you didn't say other things are not working.

Next, underhood fuse #12 - 7.5 amp. The compressor clutch relay is also located in this fuse box.

A second issue - may or may not be related. You state the "second fan" turns on? There should be two fans on the rad. When the AC is on BOTH fans should be running. Which one is not running - Drivers side or Pass side?

Finally figured it out. It was the relay in the fuse box under the hood.

Thanks to all!

Thanks for posting your fix.

good luck