A/C not running

[Aerowerk]

Hi all,

I have a '99 astro AWD. The air stopped working. It looks like the clutch is not engaging. All the relays and fuses look ok. I don't see any voltage at the connector on the compressor. Any ideas?

Thanks,

Bryan Cotton
Millport, NY

[v8famvan]

Hey Bryan,

Most likely your a/c system is low in charge. To test if that is the cause, some pressure gauges are needed to check the system pressures.
A quick test to confirm that the rest of the system is electrically ok, is to jumper the pressure switch at the accumulator - large aluminum can on the passenger side of the engine compartment. If you have your vehicle running & your a/c turned on when you jumper this 2 wire connector, the compressor clutch should turn on. Just do this to confirm that the electical control system is ok - don't leave it jumpered. If the clutch does turn on, you likely just have a low charge issue.

[Aerowerk]

Thanks James. I'll check the charge. I guess there must be a sensor that won't kick on the compressor if the system pressure is low, if I understand what you are saying.

-- Bryan

[Aerowerk]

Hi all,

I put some charge on my a/c system. Now the compressor runs intermittently. That's the progress. But it seems like it kicks on for 3 seconds, then shuts off for 10 or more. No cold air to speak of.

On the kit I bought, it has a little gauge. 0-25 psig is low, 25-45 is ok, 45-60 is the caution range, and over that is the 'danger' range. The gauge only reads when you are not pulling the trigger. I missed that fact and was putting in a can of refridgerant and I got it at about 55 when the compressor is not running. But when it kicks in, the pressure steadily drops down to about 20, and the compressor kicks out. Initially I was panicked about the 55, but I'm starting to think that the pressure they are calling out is when the compressor is running. Since it runs and pulls the low side down below 25, I'm probably fine and need to add more charge. Does this sound right?

Thanks,

Bryan Cotton
Millport, NY
99 Astro AWD

[v8famvan]

Yes, you are on the right track. It needs more of a charge & yes, this is a cycling (on/off) system.

[Aerowerk]

I did continue to charge the system. It got to a point where the compressor stayed engaged and I even got cold air to pump out. I charged it to about the middle of the range, estimated 30+ psig on the gauge.

Cold air is pumping out of the rear A/C. But in troubleshooting the ac problems, I realized that not much air is coming out of the front vents. I turn on the fan, I hear the fan noise under the dashboard. Sounds like a lot of air is blowing somewhere. But for the life of me I can't figure out where it is going. Are there any known problems with either the selector switch, the mechanical valves, ect that divert the air between the dash/foot/defrost vents? This may be a different topic than the A/C not working but rather than start a different thread I thought I would keep going here.

Thanks again James for pointing me in the right direction on the charge.

-- Bryan

[tripplec]

As you know it has to blow somewhere. Top at window?, Front vents or below although flow is poor at the foot level anyway.

The selector will not prevent if from blowing it is a vacumn control switch. However, if you check the defrost vents at the window and the cold air is blowing there. That is a known ploblem. Must be tons of post on this.

rubber vacumn line degrades in the doghouse. Left rear to right side. I did mine several years ago and don't recall exactly where. But as I said lots of post read some other threads on this problem.