2001 Dakota SLD 4x4 4.7l V8... I'm not a mechanic, and I don't have many tools, but I do like to do simple stuff, or at least diagnostics, before bringing the truck to the mechanic. I like to at least sound like I'm informed...

Recently I noted that my AC had stopped being cold, so of course I recharged it. I noted that the clutch is not engaging, even after waiting a bit after recharging and checking again. The air is plenty cold now but the clutch hasn't engaged in a while now. All that happens when I turn the AC on is the idle speed goes up.

First, could this be a simple fuse problem? If so, which one? It's not obvious which might go to the AC.

Somewhere in the cobwebs of my mind, I seem to remember that maybe the clutch can get stuck off if the freon gets too low (which it did before I recharged it), and there's a way to force it to engage? Might be way off on this!

Anyway, if there's any simple fixes I can try, or simple ways to diagnose the problem so I know what needs to be repaired, I'd appreciate any advice. I don't have a voltmeter.

 

It may be just too low on refrigerant. How much did you put in? Jump the low pressure switch momentarily. That should force the compressor clutch to engage. There is fuse for the compressor. Not sure which one it is. If the fuse box lid does not have a fuse legend printed on it, you can just pull them all out one by one to see if one is blown. You can get a voltmeter for around $10. You should invest in one and also a chiltons or haynes manual if you are going to be doing any kind of do-it-yourself work on your vehicle.

 

It can also be overcharged. If the pressure is to high it won't engage the clutch either.

Put a real set of gauges on the system, not from a can, and check the high and low pressures. You'll have to jump it for the test.

 

stick a screw driver in one of the ac lines and see if any refrigerant comes out, if it dosent its empty or low. If it dose, check the levels with a proper gauge. Been mentioned that you could of put to much in there.

Get a voltameter and check your fuse, you should have a clutch fan relay for that model (might want to google that) and make sure you getting 12 volts on the positive.

turn the truck on (dont turnt he motor) and have somebody near the ac compressor. Turn on the ac and see if the the ac unit engages, you will hear a click and fan sound start. Be sure not to mix the blower sound with the ac unit.

It could also be possible that your one of your pulleys could be off and your belt not properly grabbing the ac pulley.

If you want to be lazy, if there is a AMCO around you, they do free ac testing.

 

This is crazy don't do it unless you understand how dangerous it is and wear the proper protective eyewear.

 

its not a issue, just dont smoke.

 

All it will tell you is does the system have any pressure in it nothing more than that so as a test its worthless anyway as he pumped Freon in it already.

Gauges that's what you need

 

Yea, please don't go sticking screwdrivers in the pressure ports. Ever had r12 sprayed into your eyes? Me neither and I never want to. Get the system properly checked if you don't have gauges or know how to use them. The jumping of the low pressure switch will only tell you your low in refrigerant.

 

Just so I'm clear - if I jump the low pressure switch (and I'm sure I've done this in the past, now that I think about it), what reaction means what? I mean, if the clutch engages, that means I'm too low (or too high) in refrigerant, right? But if I jumper and the clutch still doesn't engage, does that tell me anything specific about where the problem is?

 

First, the a/c system doesn't use R12, it uses R134a. R12 was fazed out about 1992. R134a isn't poisonous, but can cause some frost bite right out of the can. He isn't gonna get any in his eye unless he can get his face right down close to the shrader valve when he pokes it with a screwdriver. Otoh, poking the shrader valve with a screwdriver won't tell him much either. Could be a bad fuse, could be low refrigerant, even could be that he has a bad pressure sensor.

We all want to do for ourselves, and don't want to PAY someone whose qualified to diagnose problems. Fine. But with A/C, if you don't know what you're looking for, or have some basic idea about what the system does, you are well ahead to take it to a shop and say, "I added some refrigerant because my a/c, and that didn't fix it." And let the guy who's trained and certified by the gov't have a look and see what's actually going on.

It isn't lazy to get things you don't understand checked out by someone who does.

Lots of places, they'll check your A/C for nothing, but even if they charged, it usually isn't more than about $40 or so. Dumping R134a into a faulty or leaky system is wasteful and foolish.