1985 FJ60 AC troubleshooting help needed!!

[dshock]

During a 60 mile drive today the AC in the truck slowly got warmer. I have had the AC freeze up a time or two on extremely hot/humid days (it is 98 F). I turned the AC off and let the fan blow. When I got to our destination I noticed no water.

I started to do a little more investigation. Checked the fuses - everything ok. I noticed that at idle, the high idle wasn't engaged. Upon further inspection the AC clutch wasn't engaging either.

I put a jumper to the clutch and everything works - cold air. Of course, no temp control.

So what do you'll think? Is there a relay, thermostat, or other control that I can replace or troubleshoot?

Thanks in advance for your help!
Dan

 

[Michael Hanson]

Froze up,give it a couple hours to melt ice.Then charge system with prob. 1-2 lbs.freon for that year should be R-12,use manifold gauges or if you dont have them get a a.c. man If its been several years prob. a very slow leak,leaked out this summer look for a major leak that needs to be fixed. 2 cents Mike

 

[upwindpoint]

Without the high idle the A/C clutch won't engage no matter what. There's a module on the face of the condenser box ( right under your glove box) that has a knob to adjust at what RPM the clutch engages.
As far as the warming up- yeah- frozen solid or leaking.

 

[dshock]

upwindpoint, thanks for the tip about the module on the condensor box. It could be part of the problem.

Just to clarify - it is not freezing up, this time. When it was blowing warm air, I pulled over even after 20 minutes of sitting engine off - fan running, there was no water running out of the truck, at all. In previous cases, there was a puddle 3' in diameter. This is a different problem than what I experienced before.

Regarding Freon level, it could be low - it has been at least 3 years since anything was done to the AC on this truck. However, if I jumper the clutch it blows cold - so at least for now it is not so low that Freon level is the cause of it blowing warm air - though it is likely the cause of me experiencing coil freezing, on previous hot days.

The signal is not coming through to turn on the clutch and/or activate the high idle. Somewhere in the electrical circuit there is a fault. From upwindpoint's comments, it could be the high idle solenoid at fault. Are there other items?

We will see what I can figure out with the FSM, tomorrow.

Thanks,
Dan

 

[Granite Grinder]

I believe that if the freon level is low, the clutch won't engage.

 

[dshock]

Anyone have any info about low Freon level causing the compressor not to be energized. If there is a low pressure safety or something that would actually make sense based on my experience with the truck. How can I verify this?

Thanks,
Dan

 

[Granite Grinder]

Anyone have any info about low Freon level causing the compressor not to be energized. If there is a low pressure safety or something that would actually make sense based on my experience with the truck. How can I verify this?

Thanks,
Dan

That I can't help you with, but I do know the compressor is lubricated with the freon, no freon = no lubrication. It's a fail safe so you don't burn up the compressor. Might try a search, there has been lot's of discussions about AC in the past.

 

[upwindpoint]

FSM says there IS a low pressure switch, not sure where it is though.

 

[torfab]

Chances are you're low on freon, and it's time to replace it. The pressure switch is in the condenser box, and it will turn the system off to prevent the pump from burning out.

If you've already switched to r134a, then I would suggest refilling the system with a bottle from the autoparts store. If not, then this might be the time to do that - the shop will just install a high and low pressure port to the system and refill it with r134a after evacuating the r12.

 

[dshock]

Well guys, the plot thickens....

We filled it with R12 today (frankly, I think that i may be a little over full - any ideas how to tell - I watched over his shoulder, and felt that he was mostly concerned about emptying the second 14 oz. container - rather than leaving me with the optimum charge).

So now, the compressor is cycling too short. It only cools the vent air to about 57 degrees before kicking out. And, the air climbs back up to about 70 before it kicks back in again. I am not sure what is going on - and I am no expert here, so any relevant education is welcome.

I jumpered the compressor and let it run and it was blowing 48 degree air after about 5 minutes at idle speed. This makes me think that the issue is largely related to the cycle and not the compressor, evaporator, condensor...

From searching I have a few questions:

1) what is a expansion valve and what happens if it goes bad? I noticed that the previous owner had to replace it about 9 years ago.

2) what are the symptoms of a bad compressor? I have 200 psi on the high side when the compress ro is running. And, the leak seems to be very slow, so I don't think that the front seal or other compressor leak is to blame.

3) dryer?? do I need to replace the dryer periodically?

4) pressure switch? Does a late 1985 have a pressure switch? From the reading that I have done, there seems to be some disagreement about whether the early trucks have one or not. And, we couldn't locate it, today.

Thanks,
Dan

 

[Michael Hanson]

R-12 mine blows 38 degrees. You have a leak somewhere and are not holding pressure,thats why you needed more freon.Look for oil leaks at connections and compressor and condensor. 2 cents Mike

 

[dshock]

It had last had the AC serviced in 2001. It has very slowly been loosing freon...

We inspected it for leaks, and don't see any evidence of leaking oil/freon.

Something happened when I was driving it on Friday. It was working ok and then it wasn't...in a matter of minutes. I added Freon, but that isn't the problem (at least solely...). Something electrical is causing it to short cycle... or something is wrong with the mechanical system (dryer, expansion valve, etc.).

Any help is appreciated.

Regards,
Dan

 

[1972FJ55]

From what you're describing, the system works fine, except it cycles off before cooling adequately. It's possible that it's overcharged, usually you will see the high pressure gauge reading 300+ , and the low side will be high as well. When charging, you want to just clear the sight glass-no bubbles. To try and answer your questions, 1) if the expansion valve were going bad, usually the low side pressure will be very low <15psi or it may go into vacuum. It could also stick open, in which case you'll have high low side and low high side pressures. 2) If you have a slow leak, and no visible signs, it may very well be the front seal, but I'd leave it alone if the leak is slow. 3) As long as the system is sealed, no need to replace the drier. 4) I think that there is a low pressure switch on the line by the expansion valve in the evaporator case.
I suspect the amplifier adjustment may be off. I'm sure I've seen some posts on how to adjust it.
Does it cool better at speed versus in traffic? I'm wondering if there isn't enough airflow thru the condenser. You might check it for debris or the fins being folded over. How's the fan clutch?
Good luck,
Rex

Well guys, the plot thickens....

We filled it with R12 today (frankly, I think that i may be a little over full - any ideas how to tell - I watched over his shoulder, and felt that he was mostly concerned about emptying the second 14 oz. container - rather than leaving me with the optimum charge).

So now, the compressor is cycling too short. It only cools the vent air to about 57 degrees before kicking out. And, the air climbs back up to about 70 before it kicks back in again. I am not sure what is going on - and I am no expert here, so any relevant education is welcome.

I jumpered the compressor and let it run and it was blowing 48 degree air after about 5 minutes at idle speed. This makes me think that the issue is largely related to the cycle and not the compressor, evaporator, condensor...

From searching I have a few questions:

1) what is a expansion valve and what happens if it goes bad? I noticed that the previous owner had to replace it about 9 years ago.

2) what are the symptoms of a bad compressor? I have 200 psi on the high side when the compress ro is running. And, the leak seems to be very slow, so I don't think that the front seal or other compressor leak is to blame.

3) dryer?? do I need to replace the dryer periodically?

4) pressure switch? Does a late 1985 have a pressure switch? From the reading that I have done, there seems to be some disagreement about whether the early trucks have one or not. And, we couldn't locate it, today.

Thanks,
Dan

 

[Michael Hanson]

Are you sure there are no leaks at the compressor? Mike