BackinBlack00

Need help troubleshooting AC not working on my 2000 C5.

AC was working fine, last week, the dashboard flickered like an electrical short then the AC stopped working. The compressor clutch engages, ac button light blinks twice then stays on, air blows thru the vents but at ambient temperature. No apparent freon leak under the hood. No AC codes on the DIC when pulling codes.

Any ideas?

Bill Curlee

Well,,, unless you destroyed the Head Unit Electronics, I'm at a loss...

Can you put your ear to the main center vent and while everything is QUIET, change the temp **** and see if you can hear the temperature door actuator motor spin?

BackinBlack00

Bill,
Thanks, I haven't tried that, I will check that out and post back. The head unit looks and works normal, turns off/on changes temp and modes.

Is there a fuse or relay for the temp door actuator motor?

Bill Curlee

redzg

"No apparent freon leak under the hood"?
Why apparent? My leak is pretty obvious, but when it's empty the A/C light flashes and goes back out.
Seems to me I've read the ambient temp sensor is necessary for operation -- do you have real or fixed ambient air indications?

ZZ06

Have you checked your pressure? Very well could be low on Freon. Popping the hood and glancing around usually doesn't suffice.

flyingjoey

Check your Compressor is turning on.. if it isn't bypass relay under hood pull relay for ac and bridge it will force compressor to take your freon. You can add 1 can of freon should be enough to get ac compressor compress gas. Seems to me need freon. I had same problem and only way get compressor take the freon ..I had to also replace low side valve was leaking ..

huesmann

IME when the refrigerant is low the compressor keeps trying to cycle, but won't stay on. If his is staying on, I don't think it's the R134a.

ZZ06

Not always. At least not when I was having issues. Mine would come on but the air was mild at best.

BackinBlack00

No sound from the actuators, tried changing modes/redirect air to foot and windshield and that does work but still no cold air.

The compressor does turn on, clutch engages when turned on a the AC head unit. I can see it spin compared to when the AC is off.

I say no apparent leak as in trying to say nothing obvious. But the compressor turns on and stays on.

huesmann

A refrigerant leak won't be obvious.

BackinBlack00

Bill,
is the "instrument panel electrical center" same as the fuse panel under the dash on the pass side?

That is the only fuse I see on that diagram, please correct me if I'm wrong but if that is the only one, if that 10A fuse was out then the HVAC unit would not work at all and mine is working.

The problem started right after the dashboard flickered like it was a short. What AC related part would fail related to a short on dashboard? All else on dashboard works.

ZZ06

If it were me, since you say the clutch engages and stays engaged, check the low side pressure just see. You might be surprised...

Bill Curlee

Yes... The only interior fuse box is in the passengers foot well.

When you say SHORT, think of BLOWN fuse, smoke, fire and flames.

Intermittant connection, poor connection, bad ground ect.. would be more on the line of whats happening.

Check the fuse and make sure that it is solid in the fuse slot. I break an old fuse in half and insert one blade into each one of the fuse slots. Called a push pull test. The fuse blade should see equal amounts of GRIP on the blade of the test fuse blade during insertion and removal.

If the HVAC Head is functional, I dont see power or ground to the head unit being an isssue.

If the logic in the module is bad, it just plain wont work.

Some more HVAC Schematics

BackinBlack00

Finally got around back to it, just before we start the 110+ degree week next week!

Bill, thanks for the schematics, I found and checked all the fuses, all are ok. I also got me the Haynes AC book and did some reading.

Got my manifold/gauges got them connected here's what it read.

Engine off - Low side = 120 High side = 135

Engine on - Low side = 110 High side = 135

From what I read in the book, either the expansion valve is stuck or compressor is bad. Before the AC stopped cooling the compressor was a bit noisy but it was blowing cold then suddenly it just stopped blowing cold. My guess, its the compressor. Now I got to get the system drained so I can work on it. I'm looking at which compressor/accumulator/orifice tube/oil kit to buy to install.

ZZ06

I believe 8VETTE7 has the spec(as do others) for the low and high side requirements. IIRC, those pressures are off. Both of them. High side should be higher. A lot of the pressures you see will be determined on ambient temp outside. I know for a fact if your low side pressure is 110 with it running (compressor clutch engaged) it is way too high. Hence you may have found your problem.

Bill Curlee

Either the orifice tube is clogged or the compressor is shot or BOTH!!!!

redzg

Compressor is turning? For certain?