HVAC schematic for 91 OCC?

My OCC has digital HVAC and for whatever reason it will not activate the compressor clutch. I'm able to hotwire the clutch and get cold ac, but would prefer to fix! Does anybody have a schematic?

There are FSMs on ebay for under $40. The book has 6+ pages of trouble shooting for the HVAC system.

Just a though...is the clutch relay working? Did you check the fuse?

Hey Don before you do anything else just disconnect your battery for 1 minute and then
reconnect.When you restart the car dont touch the AC climate control.Let it go thru its
2 countdowns beginning at 30 and you should be fine.Dont laugh this works and its easy.
Jim

When I was testing the fuel pump power path on the chevy, I made a set of five male/female spade jumper wires to space the relay away from the plug for troubleshooting. One of the five jumpers has another wire tied in that can be used to put power onto one of the terminals or power a light in the cockpit for indication purposes.
I have determined using these items that the relay is working, and that the cycling switch is working (indicating proper freon charge) but that there is no power to the cycling switch (I'm assuming that the controler powers it)
This wagon is still on r-12 and blows cold when the clutch is engaged, so I prefer to assume the freon charge is okay. I don't have r-12 gauges and would prefer to not change over to 134 unless I have a clear indication that the problem is a less-than-adequate freon charge.
I've got the battery currently disconnected and I'm crossing my fingers!

P.S.... I really love that folks are so helpful here, and I'll do everything I can to do my part by posting up my troubleshooting and conclusions to hopefully be helpful also!

You guys are freakin awesome!
After battery disconnect and two 30-second countdowns, my a/c is now working!
I'm now noticing that the compressor clutch is engaged during heater settings as high as 90 degrees (?)
Since I hadnt noticed this before, I'm wondering if this is perhaps normal for de-humidification purposes(?)

Glad that worked for you Don.My OCC does the same thing and my owners manual says that this
is normal.When your compressor starts cycling on and off at a rapid rate it usually means you are
low on freon.I would resist changing to R134 until you absolutely have to because the R12 cools
so much better with these older systems.
Jim

AzDon wrote:

You guys are freakin awesome!
After battery disconnect and two 30-second countdowns, my a/c is now working!
I'm now noticing that the compressor clutch is engaged during heater settings as high as 90 degrees (?)
Since I hadnt noticed this before, I'm wondering if this is perhaps normal for de-humidification purposes(?)

Yes

Yup that's it. I had the same issue. My freon went down and the system recognized and correctly killed power to it. I repaired the leaky schraeder valve and filled it back up with R-12 and it wouldn't work. Drove all the way to Daytona and back, and then thought about it some more and the battery trick worked. I was pretty happy too .

I really don't want my compressor running full time when I want heat, because it diminishes and delays getting heat and because it's a waste of fuel! I'm gonna wire a switch into the blue wire at the cycling pressure switch to disable the compressor and hope it doesnt trigger continuous need for resets

Don,I just put my system in the economy setting and that stops my compressor from engaging.
Jim

Thanks Flash!
You just saved me a WHOLE LOTTA work! I appreciate the info!
Don

Don,are you being sarcastic?Sarcasm is not to be tolerated on this site!
Jim