AC in my 91 B2600 not working. AC button lights up on the first press and compressor comes on as the engine idles up slightly. Then after a few seconds engine idles back down to normal and doesn’t idle up again. Guy I bought it from says they converted it to R134, and it never really got cold after they added R134. I think it’s the compressor since it’s not clicking on and off after that initial one time. Truck only has 90000 miles and completely untouched. And wasn’t driven much at all. Any help is appreciated.

 

Budgy - the solution to your issue is to sell the truck to me if it's rust-free and nice.

Barring that, I'm in Arizona and know a fair bit about automotive AC, and on these trucks.

First of all: NO ONE converts a perfectly-working system to R134a, folks do this when they have a leak or a faulty component and mistakenly think that conversion to R134a is less expensive, but it really isn't unless one has additional leak issues. You see, R134a requires different oil than the R-12 type mineral oil, so the R-12 mineral oil needs to be removed first. OK, your system has been converted, so stay R134a at this time. If a real shop did the conversion, by law there should be an underhood sticker stating this.

I'll assume that you know how to visually confirm that the AC compressor clutch has engaged and that the compressor is turning. That means that the inner part of the compressor (drive plate) is turning when the AC is on, as opposed to just the outer AC pulley freewheeling.

Next would be to measure both high side and low side pressures at about 1800 rpm with the AC on. Post those. If you don't have a real gauge set, Autozone in warmer parts of the US has free loaner units. Post those values. So that's where to start. Also post whether your blower fan works in all 4 speeds.

However, the only REAL way to tell if the system is low on refrigerant is for a shop to pull out the refrigerant and WEIGH it with their special equipment. A real AC shop also should have a combination of UV dye/light/goggles, electronic sniffer, soap bubbles, and visual examination to look for leaks. Most likely there is a leak, as 70% of auto AC issues are due to refrigerant leaks. But adding any sealer or refrigerant containing sealer will likely ruin your AC system, and no shop will service it if sealer is in there (they test).

 

This truck is a time capsule. Absolutely the most perfect Bseries I’ve ever seen. 90,000 original miles never wrecked, interior is a strong 8 out of 10. Underside and on top of motor no leaks. Completely stock and untouched. Yes all 4 speeds work on the inside. AC button stays lit at all 4 speeds too. More than likely it will go in the shop I was hoping it would be a relative easy fix, but I’m wondering now. I would rather a shop with AC knowledge handle this one I think.

 

Should be a good idea; these systems are simple as far as AC systems go. My 1988 B2200 uses R-12 and works good in Arizona, but I've had to replace the compressor a few times and the evaporator once (leak), and needed a the high pressure line crimp professionally repaired in the 25 years I've had mine.

Fall 2018 the AC compressor seized in my 2004 Frontier at 104K miles, but the same compressor in my 1998 Frontier at 245K is still humming along; both have great AC, and both are factory R134a.

 

Well there is a decal under hood that states the R134 conversion was made, but no date or who did it on there. Just states it has been done. I have a receipt from the previous owner of purchasing a new R134 compressor I think in July of 2011 or so. I don't think it's the AC relay in the glovebox as all the speed settings work. Whats weird is when i hit the AC button in the truck, it lights up and the truck idles up slightly for a second then goes back to normal idle. Hoping its a simple issue when I take it in. But the clutch doesnt engage at all. Can overcharging or undercharging cause the compressor not to engage?

 

Undercharge would cause the compressor clutch to fail to engage.
With an overcharge or a blockage, compressor clutch could engage for a very short time, then disengage to protect the system.

Sounds like the shop visit is a good idea, but maybe wait until spring. My guess is that there's a leak which needs to be found and repaired. Good that it seems that a shop did the conversion.

 

Well, come to find out it was just low on refrigerant LOL. Put one can in today and the compressor kicked right on. So it was really low and when one can was added the gauge was just into the "Acceptable" GREEN range. Should I add another can and get that in the middle of the GREEN good to go range? How many ounces of refrigerant does this thing take? That would be two (2) 12 ounces can added once I add one more can this evening. I would like for the gauge to read about in the middle of the GREEN range on the gauge.

 

NO ! And especially NO if you added refrigerant that contained any type of a sealer, like AC Pro. Because now you have a compromised system that no shop will ever work on, their equipment can detect sealers, and that contaminates that.

Bud - if you were that low, you have a leak that should be fixed, illegal to add refrierant to a system with a known leak except for leak detection investigations. You really need a set of real R134a service gauges https://www.harborfreight.com/search...%20gauge%20set, or at least get loaner set at Autozone. Because refrigerant is best added by weight, and the ratio of refrigerant to refrigerant oil is pretty critical. Unless one charges refrigerant by weight, your best chance of getting close is by the HIGH side pressure at about 1800 rpm, not the low side pressure.

Since you're not likely to listen to me, I'd say capacity for R134a would be about 24 to 26 oz. If you vent the hoses properly, maybe you can get 85 to 90% of the can contents in. But if your system really needs two cans, then it was almost empty. And will be empty again pretty soon.

 

I added refrigerant that had no anything in it. Just refrigerant. I know not to use stuff with stop leak or other crap like that in it.
Yea there may be a leak. And I plan on getting it looked at as soon as can.

 

Great.

You can look for oily residues at fittings, hose crimps, etc. for a visual examination. You can also buy a big container of kids bubbles at Dollar Tree and put that in a spray bottle and look for bubbles. Using UV dye/light/goggles and electronic leak detector involves more equipment, may be better left for an AC shop. I use a combination of all four techniques to try to find leaks. Don't overlook that service valce caps are a big part of keeping refrigerant in.