1990 vette
The Automatic Climate Control has no display and the heater-fan is running full on. The buttons are all unresponsive. There is a backlight to the system, so I know it is getting power, but nothing shows on the display

 

Check the '90 FSM, Section 8A, for diagnosis. You should find a flow chart leading you through the procedure step by step. The info is quite detailed.

 

guess im going to have to find a manual to buy

 

Plenty of sources, new and used. Originally published by Helm, Inc. Most aftermarket vendors sell them. Could be on the CF "For Sale" forum or Ebay. Get the red, not white, covered edition.

 

Gotta love eBay.

Just picked up the FSM 3 book set for $50 used. Soon I will be tracking down problems like a pro.

 

That's the best move you could've made. Post back with your progress!

 

I don't have the 90 prints but don't assum it is getting proper power. Some of these boxes get power from multiple sources. Check ALL the fuses first carefully, you might find something. Fuse links or Maxi fuses to. Check connection on rear of controller.

Additional suggestion;
Also look at the connector for the blower module on the top of the evaperator box. Look at the pins and wires to see if anything looks burned. I beleive an open connection can make the blower run full bore.

 

well, no point in coming here for advice and then not following it.

 

Not sure where your going with this post...but you may still need some additional "help".

This time of year is "fraud" central for Fleabay (record numbers this year from what I understand) - I do hope you actually get what think you've "won". You can get the occasional deal on there but there is a ton of garbage on there and it is all "buyer beware." If everything goes well $50 is a super sweet deal for all 3 of the "complete" books (3 red FSMs to include the LT5 and the related supplements would be "complete").

The FSM you've acquired will contain some basic versions "black box" type of the AC electrical diagrams (non too specific though) for most portions of the control head's internal circuits but with it and a voltage meter in hand you should be able to at least find/do some basic input/output voltages to checks.

From what your describing if the rest of the AC system is "ok" then your controller is most likely problematic/"toast"..which is not that uncommon for the 90+ C68 units. I have heard of people repairing or having these units repaired though - you may want to do some "searchs" here on the CF. I you decide to replace it totally, and if it were me, I would not buy a replacement control unit off of flEaBAY (probably was removed problematic units already) - you'd have much better luck actually getting fully functional working unit from a CF "parts" VENDOR.

 

As a general rule, I would not buy electronic pieces from eBay

Especially not used ones.

And used is where you get the best deals on eBay.

most times I find as good or better deals on new items on amazon.com

 

If you pull the controller out, I would at least look very carefully at the solder connections. Especially the bigger pads. Re-flow anything that looks cracked.

Check the pin connections for the interconnecting boards and clean them.

Worth a shot.

 

Check the AC Clutch Fuse in the drivers compartment fuse box.

 

wow, a LOT of things to check, hard to believe how complicated it is, don't suppose there is a way to eliminate it and use a mechanical system?

 

There are 60s cars still out there.........

 

You could just forget the whole thing, and open the window if it gets hot.

 

A simple no would have worked

 

Yeah but C4s aren't simple.

Even disabling and removing systems requires extensive knowledge. just yanking something could leave a car disabled. I sure spend a lot of time in the FSM. It's pretty worn after only 10 months of ownership.

 

No offense intended- sometimes a little fatalism helps keep us sane.

 

NO, really i appreciated the comedy LOL