Jim Lane

Well, this could not have happened at an uglier time, the other night I started up my truck at a job and I heard a high pitched whine coming from under the hood like a bad bearing and then I also smelled something burning like plastic, I stopped in a very dark parking lot to check and determined I could make it home.

When I got home I checked under the hood, all of my battery connections but I found nothing wrong, but by now there was no small or sounds.
So today I noticed my air conditioner was not very cold, fact it was almost nonexistent, when I came out of the nice cool West Covina Mall after lunch at Red Robin I found my cab was 135*
So I took it home and started check it out.

R-12 refrigerant.

With the gauges installed:
Low= 50-60 PSI
High= 160-175 PSI @ about 1000 RPM
Ambient Temp. 98*
Evap Temp. 90*

Refrigerant charge was slightly low, throttle up and let off, you can see a wave float past the sight glass but no bubbles or streaks.

Rev the engine to about 1500 RPM:
Low= 38 PSI
High= 190 PSI
Ambient Temp.= 99.9*
Evap Temp. 80*

All of the components appear normal, no leaks.

I am thinking the compressor is bad or possibly the condenser, after I had replaced my evaporator with a new aftermarket piece of junk, it has never really cooled good.

Oh yes, plenty of airflow, both electric cooling fans and an an external blower into the radiator.

And wierd part, it does cool a little at night when I don't really need it tho not much.

So people, give me some input.

Also anyone know the dimensions on the 1991 non-IC condenser so I can replace it with a parallel flow?

Thanks in advance.
Jim

209trucker

My guess would be the condenser. I had the same symptoms in my 03 Sierra, when it was hot outside, the A/C would blow air just slightly cooler than the outside temp, and at night same thing, so the air felt cooler being it was evening. Replaced the condenser and it blows ice cold now, but I'm no A/C guru either.

bigragu

Hey Jim the high pitched squeal noise you heard is exactly what mine did and sounded around 6 months ago. I saw smoke coming prom the clutch pulley area and a few hours go by I come back to the truck and see a hardened black paste on the ground directly under the compressor. Clutch had seized up. Luckily I carry a non a/c bypass belt to get me home. Swapped out for a new compressor and filer drier months later and with R12 back in all is good. I know a couple of years back my expansion valve went out which caused pressure and my freon shot out of the compressor pressure relief valve. I think for years running low on coolant led to my compressors death

thrashingcows

I too was going to say the AC compressor is seized, or working on it.

I was driving a rental Freightliner last week...when it was screaming hot, and the AC compressor did exactly as you described. Squeal like a bearing, and smoking. There was melted something coming from the front of the compressor.

Jim Lane

The high pitched whine sounded like bearing, vacuum leak or maybe even high pressure being vented from the system, it did not seem the change with engine rotation, the smell was like insulation or maybe friction material, I looked under the clutch and there looked like some flecks of maybe the clutch but it still seems to be working at least turning.

It does not look like I can get much of a differential between suction and discharge, I was trying to figure out a way to check the compressor while in the system but there is no way to isolate it.

Some of the commercial systems I work on you can isolate them with valves and check the compressors valves and pistons, Ford/ York with the Rotolock valves were an example.

Since I cannot get the suction side down into the 20's or teens I was thinking either the condenser was blocked or maybe the compressor head gasket.

The truck had been sitting for about an hour at night when it first happened so the system should not have had much pressure in it.

Last July I had replaced my leaking evaporator with an aftermarket one I got from OReilly's, I had to reject I think 5 evaporator out of the box because they were sloppy garbage, I finally got one I felt I could work with, it took about 20 minuets in a vise to massage it into shape where it would fit the case perfectly (more on that story later) the evap now fits perfectly and is completely sealed using aluminum tape.

BUT I just could not get the temps as cold as I was able to get with my old leaking evaporator, this compressor was just 3 years old.

Also what are your thoughts about installing an inline filter ahead of a Parallel Flow condenser since the passages are so minute?


Jim

sooty

check the relief valve near the high side connect, for evidence the system discharged refrigerant and oil, evidence something got restricted, condensers fail from debris discharged out of failing compressor, filter dryers fail when silicate pack releases into system, the expansion valve wont pass any debris, a partial restriction after discharge, will bring pressures back down, with reduced cooling, if its mine, and debris is evident in system, id start from scratch replacing to new.

bannerd

That noise is what happens when the compressor runs out of oil or improper lube. Sure the clutch will work fine but.. the rubber crank seals are probably burnt out. You would have to remove the compressor, take it apart and replace the o-rings. Hands down that is what the problem is. Without those o-rings you'll never get your high pressure charge. The compressor can crank all it wants. Sort of like my heart murmur.

Rampage1967

Sounds an awful lot like a compressor failure to me.

Angry Johnny

I would agree. I got a new condenser from Rock Auto for my 92 and it is a newer configuration suitable for R134a. I would replace the condenser, drier, h valve and compressor. Flush out your evap and all the lines.

Also I've noticed in previous posts you said your compressor didn't cycle off and on. It should cycle when the evap (actually the suction line where the cycling switch probe is) reaches a certain temperature. I don't remember what that temp is but I think it's around 34-36 degrees. If yours never cycled you need a new cycling switch as well.

I've seen your pic of the thermometer reading in the teens and that is just not right, that is really hard on the compressor.

Jim Lane

Just an update.

I went and ordered a re manufactured compressor from OReilly's Wednesday, so I could pick it up on Thursday, yesterday just because I knew it was going to be an issue, I also ordered a new H-Valve and a new receiver/ drier, he tried to give me a receiver/ drier that had been open and could not understand why I would not take it, also the computer showed the valve for the inter-cooled truck, had to straighten him out on that also.

So finally about 9;00 P.M. I got the compressor and went home, I was planning on installing it when I got home and charge it by tomorrow afternoon when it would be about 100* but no luck on getting the other parts tonight.

So I got home and started taking the truck apart, I was going to at least get the new compressor in and connected till I took the new compressor out of the box and was going to drain all of the oil out if it till I found there was NO oil in the new compressor, also with the ports open there was no way I could get the compressor to turn, it is seized up solid.
This is my typical luck that I have trying to find parts, this new re manufactured compressor is junk, so I picked up my tools and called it quits for tonight. I will have to call and deal with this junk in the morning.

I pulled the head off the old compressor and found the reason it stopped working, I found bits of plastic stuck under 2 of the reed valves holding them open, looks like the plastic coating separated off from the inlet gasket and got sucked into the compressor.

Jim

Angry Johnny

Not sure on the non IC trucks but I was able to get a new compressor for mine.

maybe368

Jim, while you have the system open, change the high pressure relief valve on the manifold at the compressor, it has an o-ring that needs to be changed anyway. I didn't and it failed and blew the charge, only about 20 bucks and well worth it...Mark

sooty

I got the later water outlet/bracket for the sanden compressor, modded the lines, very minimal

Jim Lane

Mark,
Thanks, I already replaced the relief valve last year after I lost a partial charge.
OReilly's didn't have a clue what they were but my local AC shop had them on the shelf.
Jim

Jim Lane

This is what I am planning on doing in the future just not in the middle of a heat wave however I have not had luck in finding the lower water outlet/ compressor mount, the SD-709 is not the perfect replacement but new larger displacement compressors are readly avalible, I also want to make some custom hose connections that are easier to repair.
Jim