First off, I'd like to say I partially know what Im talking about so this may be slightly interesting for experts.
I purchased this truck used, I have never seen the a/c work. The blower works fine, and the vent selector works.

The compressor will not engage unless I manually hotwire it to the battery.

I have jumped the lowside & highside pressure switches

I have swapped the compressor clutch relay under the hood.

I started to change the interior control switches, but I can feel the relay click when my wife turns the control **** to a/c, so Im assuming the control ***** are fine.

What is between the relay & the compresor that could be causing it to still not come on?

 

99 dakota v6

 

You need to put a gauge set on and get a reading first.

Then we can answer that.

Find a shop that does a free evaluation if you can many will.

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You have two sensors on your system a 1999 Dakota a low side and a high side. One checks the low side pressure the other the high side pressure if either is out of range the A/C will not engage the clutch will not engage. If you are forcing it to engage when it doesn’t want to you are in danger of burning up your compressor. There is usually a reason the clutch is not engaging forcing it to engage is only used to test things out not to keep it running.

Note I have rarely seen those sensors go bad but it can happen

Click on my bottom sig and go to page #3 for more info

 

Im not trying to keep it running. Im only trying to test the system before I go have it recharged. Obviously there's a problem if it wont try to engage when I jump both of the sensors. Im simply trying to make sure the system will even engage before I charge it, it seems like there is a electrical problem somewhere.

 

If you can force it to run by jumpers then all wires are working. Correct.

Just the fact you can get it to run with the jumpers says the wiring is OK.

 

Im confused at first you said you could get it to work with jumpers now you say it will NOT?

 

I don't think I explained my situation clearly in my intial post.
The only time I have ever seen the compressor clutch engage is when tested it by jumping it straight to the battery for a second. Other than that, it will not engage, whether I jump both switches or not. I know for a fact I have a freon problem, but Im not going to have the charge done until I know why I cant just fool this compressor into coming on for a second. I can feel the PDC's Compressor Clutch relay click when I have my wife turn the ac **** WHILE THE SENSORS ARE JUMPED. But what could be stopping it from attempting to come on? If the sensors are jumped, the system doesnt know there is a freon issue, right?

 

Your compressor may be frozen/busted up and will not turn at all.

 

Have you see the compressor turn over at all?

 

If I undo the compressor clutch connector & hotwire it directly to the battery, it will engage.