I have acquired a 1992 lumina with a 3.1engine and an odd problem. The AC and the speedometer only work together. Is there a connection between the two? Sporadically both come on and work fine. I figured the speed sensor to be the speedo problem but I'm unsure how it can affect the AC. And by AC I mean the compressor, the fan blows but the compressor doesn't engage. Any help would be greatly appreciated as this car is in other wise great shape with only 70k miles.

 

You got two different problems. Check voltage to the clutch. The speed sensor is probably bad, does it shift when the speedometer is not working?

 

Thanks for the reply. I'll check the voltage, but shifting is fine no matter if speedo is working or not, but if the AC works then the speedo works or the other way around. There definitely seems to be a connection. I have had so many other things going on I just haven't had time to work on it

 

I can't see any correlation between the two, but either Haynes, Chilton look at the wiring schematic see if there is something both have to have to work.

 

Looking at an electrical schematic, shows speed sensor input to ECM, and output to A/C system, both are next (physically) to each other. I'd suggest pull the connector, and use a non conductive electrical cleaner. Don't overtighten the connector when reinstalling it. Give that a shot.