Alright. So today I went to turn my ac on and all that came out was hot air. And on top of that, the rear hvac won't turn on. When i try to turn it on, the OFF just flashes three times. And I can't turn it on. I checked the pressure and it is okay. I pulled the fuses to reset the system and still nothing. I also tried switching the relays and that didn't work either. The thing that stumps me is that even though I turn the ac on, I don't hear the clutch kick on. Any thoughts??? I'm really hoping that the compressor is not shot. Thanks.
Great! No AC!
- Thread starter agon3279
- Start date
Without doing some basic circuit troubleshooting it would be tough to say.
I would inspect for poor connections of the following three items and their circuits.
A. Compressor temp sensor
B. High Pressure switch
C. Low Pressure switch
Also not ruling out the head unit as a cause. Could be bad connection.
I would inspect for poor connections of the following three items and their circuits.
A. Compressor temp sensor
B. High Pressure switch
C. Low Pressure switch
Also not ruling out the head unit as a cause. Could be bad connection.
djthumper
Administrator
How did you check the pressure and know that it is ok if you also think the compressor may be gone? You should be reading the pressure when the system is operating. Generally if the clutch isn't kicking in I would look at one of the pressure switches. I would probably take a look at the low pressure one first as it is fairly simple to get to.
DJones
Member
I had a problem with my A/C that I fixed about a week ago. It hadn't worked for two years and then one day I started discovering problems:
1: The A/C condenser NEEDS air forced across it to work... going 70MPH isn't enough. Not a problem with most users, but I have an e-fan but I didn't have the A/C wire connected. I connected it and then it worked ... for about a month.
2: The clutch plate toasted... looked excessively worn with grooves in clutch plate and pulley. Replaced the clutch plate and it worked... for about a month... on my way back from North Carolina it quit again.
3: The pulley bearing toasted. Removed the engine belt after excessive noise was heard and the pulley was found to be extremely wobbly. Replaced it and my A/C has been blowing ice cold for about a week.
Based on my experience, if I were you, I would check to see if the electromagnet was energized. Mine was always, so I could use a crowbar to "start" the compressor, but it wouldn't stay engaged for long. Then I would check the pulley for wear.
1: The A/C condenser NEEDS air forced across it to work... going 70MPH isn't enough. Not a problem with most users, but I have an e-fan but I didn't have the A/C wire connected. I connected it and then it worked ... for about a month.
2: The clutch plate toasted... looked excessively worn with grooves in clutch plate and pulley. Replaced the clutch plate and it worked... for about a month... on my way back from North Carolina it quit again.
3: The pulley bearing toasted. Removed the engine belt after excessive noise was heard and the pulley was found to be extremely wobbly. Replaced it and my A/C has been blowing ice cold for about a week.
Based on my experience, if I were you, I would check to see if the electromagnet was energized. Mine was always, so I could use a crowbar to "start" the compressor, but it wouldn't stay engaged for long. Then I would check the pulley for wear.
djthumper said:
Step #1 in troubleshooting the AC system according to the service manual is to check the static pressure. This is to ensure further testing does not damage the compressor. Such as jumping the clutch, etc.
The static pressure should be equivalent to the ambient air temp. So if it is 90F out then the pressure should be about 90 PSI on both the low and high side.
The head unit could cause a problem with the ac?! Or do you mean it could cause a problem with the rear havac? I did just change the front and rear speakers. Well when I hooked up a pressure gauge to the system it was in the green even though the clutch didn't go on. Now I only have simple gauge so as far as the pressure i probably have to go and get it checked by a mechanic. I also unhooked the low side pressure switch and that didn't seem to do anything at all.
agon3279 said:
According to the schematics the rear fan selector switch down by the shifter connects to the main hvac control head up front. It's just one wire. Grey I think.
So if that knob isn't doing anything it could be the power feed common to them or the hvac head unit itself.
I would invest in or find a schematic to troubleshoot if you are so inclined. If not, then taking it in is about the best option for you right now. That is unless you know where the wiring got screwed up when the speakers were being messed with. If the head unit has power then don't suspect fuses. But just in case you missed it, the fuse is HVAC 1.
ok. at this point i am stumped. Today the ac turned on and worked fine. Also, the rear hvac controls worked to. I really don't know 
agon3279 said:ok. at this point i am stumped. Today the ac turned on and worked fine. Also, the rear hvac controls worked to. I really don't know
Loose connection, relay going bad or gremlins. lol. But hey as long as it works now then that's great.
Wooluf1952
Member
agon3279 said:ok. at this point i am stumped. Today the ac turned on and worked fine. Also, the rear hvac controls worked to. I really don't know
I had the same problem with both my Ac and 4x4, shortly after I bought my Envoy. I would pull the fuses (don't remember which ones) and all would be fine. I'm not sure if R/R'ing the fuse cleaned the contacts, but I had no more problems after the ignition switch was changed.
DJones said:
Just wondering if you had a link on changing the bearing in the pulley and also here in canadai cant seem to find a bearing here. So i was wwondering if you had any info on it
meerschm
Member
- Aug 26, 2012
- 1,079
CaptainXL said:
R134a Refrigerant Pressure Temperature Calculator
minor correction. ambient pressure of 134a depends on temperature, but does not equate to temperature.
(for a static system with liquid and gas at the same temp.)
at 90 degrees f should be 82 PSI
at 70 degrees f, it is very close to 70 psi.
DJones
Member
Dakota76 said:
Based upon the way the pulley and bearing are assembled, I think they are one unit. I pulled the replacement off of an used A/C compressor. (This helps to learn how everything goes together) After using heavy duty clip ring pliers to get the clip ring out, the pulley is easy to pull off with the correct rented tool. I have seen others on here with new pulleys and clutch plates, but I'm not sure where they got them.
meerschm
Member
- Aug 26, 2012
- 1,079
http://gmtnation.com/f23/ac-clutch-replacement-7718/
you could call the place in Floriday listed above (after a long story) see post number 9
they put together a rebuild kit.
might sell you just the bearing, or bearing with pulley.
not sure if they ship to canada.
good luck
you could call the place in Floriday listed above (after a long story) see post number 9
they put together a rebuild kit.
might sell you just the bearing, or bearing with pulley.
not sure if they ship to canada.
good luck
meerschm said:
If you look at the chart again you will see the above isn't right. It isn't 82 PSI
At 90 degrees f should be 105 PSI
This second part is right.
at 70 degrees f should be 70 PSI
This is with a completely cool engine in the shade and the system has been at rest for many hours.
It is impractical for mechanics to wait this long. The static pressures are only to see if there is sufficient charge in the system so it will operate unharmed. Then low and high operating pressures can be made with the AC on high. This is per the service manual when doing a proper performance test.
In summary (according to the service manual) If pressures are good and the actuators are working properly but still not cool enough out both center vents then the system should be evacuated and weighed. Then refilled properly with the correct weight of refrigerant.
