My AC is freaking out

[melinhead]

It's getting hot around here, well relatively Montana hot, but the AC is freaking out. Did a search and didn't really find a satisfying answer. Here is the situation.
1996 LX450 with 147 on the clock, bought it about 6 months ago and everything works great. Bought it with a brand new AC compressor. But the AC is freaking out. (Really first time using the AC, may have bought it with the problem)
Turn on the AC and it works fine and cold for the first min or two then there is a either fast or slow rhythmic clicking which sounds like it is coming from behind the dash, probably the heater control area. I can't tell on the fast clicking but on the slow clicking it seems to be turning the compressor on and off with the rhythm of the clicking. The RPM will flucuate a hundred or several hundred rpm in sync with the clicking. So I am guessing it is a control issue. No problems what so ever on the heater side it works like a charm. So do I need to swap out my whole heater control unit, or is there a specific AC part of the control unit that needs to be checked. Or is it an under the hood type of a problem? Any ideas or insight would be helpfull, and if I have to pull the dash and swap the control unit, any tricks to doing that?
Happy Mudding

 

[Dave 2000]

I am no AC expert so take this as you see fit, if nothing else it gives your post a bump. The compressor needs certain conditions to be met before it engages and stays engaged, things like gas pressure is one of them. If the compressor engages and then finds the pressure is to high/low it disengages the pressure alters and it re-engages and so forth. If you have an electric fan that is not working correctly or poor flow from a viscous unit this can cause this problem. If you find it stays engaged longer if you are driving at speed i.e. air flow over the condenser is higher then this might suggest insufficient air flow at low speed or idle. If you have the AC system with the 'AUTO' setting then the temp sender in the car could be to blame. I would have the system regassed before doing anything as again the pressure could be wrong.

Sorry I cannot be more helpful,

regards

Dave

 

[Truckasaurus]

Amp

There's an amplifier that has the misery of being in the wrong place, slightly to the left of the main HVAC control panel, which, if your windshield has ever leaked, a little water may have leaked down into it, corroded, etc.

Do a search for a/c amplifier. A couple other guys here have had to get elbows deep to remove/replace.

How do I know? I had a similar situation, where the LED's in the HVAC control panel would turn on, then all pop off simultaneously. Needed the truck to dry out a bit, so it was a random drop of water, not a long term corrosion thingy.

On the one hand, I hope that helps. OTOH, it's a spendy fix...though I'm sure you could do a 'WTB' on the Parts for Sale section, since there are quite a few 95-97's out there getting shredded.

Good luck!

 

[melinhead]

I'll check those things and my brother in law across the street has a code reader and I am going to see if it is pulling any wierd codes. Still quite a mystery. This is happening whether I am sitting Idiling or at speed on the highway. I am not sure that moisture is a prob but I can check the a/c Amp. I am hoping that the code reader will tell me something.

 

[Dave 2000]

I would get the pressure checked before touching anything else, these systems lose some pressure over time in particular if not used often during the winter.

regards

Dave