A/C Question 1985300SD
 

I cannot get the compressor to engage. I ran a direct line from the battery and the compressor runs fine. I have bypassed the pressure switch but that did not help. Does anyone know of any shortcuts to find problem I am tempted to run a 12 volt switch to compressor,it is hot in S.C. Help

I don't know if the 1985 SD's A/C is the same as the D and TD, but there is a thread going on right now related to those that you should check out:
http://www.peachparts.com/shopforum/showthread.php?t=225509

No... bad idea. The various relays involved provide info to shut the compressor down not only when you have enough cool air, but also when there are other problems that could ruin your compressor (or even your engine) if it didn't disengage. Troubleshoot the problem or take it to someone who can. If you want to do it yourself, then jump in on the other thread - also good to see if you can get the wiring diagram for your system. If you don't have access to one, you can ask around here and someone can probably help you out with that.

Why is everybody always looking for shortcuts?? Troubleshoot and fix the problem. :idea:
I'm just sayin'..........

You want to check out <Klima> testing in search. My '84 just has a relay, but in '85, I believe they went to Klima. One guy here has a whole list of shortcut tests to figure it out. Wish I could remember who it is, but it was someone smart and creative.

Shortcuts are nothing more than a quicker path, found by trailblazers, and passed on to others. Think of the Oregon Trail, Panama Canal, etc. Nothing wrong with intelligent shortcuts.

Here's the entire set of tests to determine the issue when a Klima is present. Note that the vehicle is an '87.............the '85 is slightly different.

http://www.peachparts.com/shopforum/showpost.php?p=1546012&postcount=70

I believe on the '85 there's a switch on top of the camshaft cover which opens the compressor circuit during full throttle.

Kilma switch
 

I read a link where you could short out jumper #5 and 7. I did that and A/C started working. Does that mean that kilma relay is bad or what. This was what I was asking for when I asked for a shortcut. My 1984sd does not have a Kilma. Thanks for the input.

As far as I understand it, jumping pin #5 to #7 is simply putting 12 volts to the compressor. Again, you could do it if you want, but it's not really solving the problem. Either the Klima is bad or something feeding info to the Klima is not functioning properly - or something else is wrong (low refrigerant) and the sensors and relays are fine and doing what they are supposed to be doing. Now, that might not help you much, but you'll have to dig around to find out. Try jumping various sensors (i.e. low pressure cut-out, etc) to see what you get - the more info you have the better off you will be. Have a look at the Klima first and try to find a wiring diagram.

You might find something useful here:

Kilma relay
 

First of all I would like to thank all for the information provided. The pressure switch is good. I am in the process of checking out other things. I jumpered #5 and #7 pins on kilma and the compressor works. I will troubleshoot and use the process of elemination. I had no idea that the kilma looked at so many functions. My 1984300sd does not have one on it.