1989 r1500 burb, 5.7 AC troubles.

Wasn't sure where to post this, so this seemed like the best place. I'm having some issues with my AC, and looking for answers as to where to start. I have an idea in my head what the problem is, but I wanna see peoples opinions.

Ready?......


Here goes.


I just recently converted to R134, purged almost all of the R12 or whatever out. Drained the compressor and blew all the mineral oil out of that too. Did new o rings and seals, new orifice tube, new air dryer put 8oz? Of PAG in the compressor. Pulled about 28 or 29" on it for hour and half, then charged with... 48oz of freon. R134. (whatever quantity the manual called for rear and front AC), I knew I had to get the amount right because towards the last can, the compressor wasn't kicking out anymore.


When I turn the AC on, clutch engages, AC starts blowing out "fairly cool" that's not an issue. But the truck goes from a nice cool 160 like it always runs to sometimes 180-190? When driving around town. AC still blows out nice and cold.

And if I have the truck just idling in park, the truck will be running more like 210 if left for 45 min, and AC isn't even cold anymore. This only happens when I run the AC.

The truck will idle for hours at 160. No issues with engine cooling or anything until the AC is running in park. Truck has always ran really cool with the big HD radiator in it.

Any tips or advice would be appreciated. Have a beach trip coming up soon and don't wanna ride around everywhere with windows down for ONCE in my life. Lol

Fan clutch issue? And add an additional electric fan. I ran HD clutch fan and different fan blade on mine.

yevgenievich said:

Fan clutch issue? And add an additional electric fan. I ran HD clutch fan and different fan blade on mine.

Click to expand...

Does the AC running normally increase engine temperature?

Like I said the truck stays at a cool 160 at all times until the AC runs.
It'll stay running at 160 for hours and hours just idling.

It's only when I have the AC turned on it starts getting hot, and like I said, the AC will stop blowing out cold.

I agree, it sounds like you're not getting enough air through the condenser and radiator. I bet your high side pressures are up there too when it happens.

Markmx6 said:

I agree, it sounds like you're not getting enough air through the condenser and radiator. I bet your high side pressures are up there too when it happens.

Click to expand...

Ok I guess I should've expressed I'm kinda dumb when It comes to this AC stuff.

So you think the condenser is getting too hot?

And increased high side pressures kill the cool AC?

This truck 5 or 6 years ago ran with AC blasting cold (R12) idling at hot outdoor temperatures and didn't have these issues.

That's what confuses me.
What changed.

I'm trying to ensure i didn't screw up somewhere.

R134 runs higher pressures. And fan clutch could be weak as well compared to before.. Also with conversions, I don't follow exact charge amounts and go by pressures and performance.

yevgenievich said:

R134 runs higher pressures. And fan clutch could be weak as well compared to before.. Also with conversions, I don't follow exact charge amounts and go by pressures and performance.

Click to expand...

I'm wondering if
A I didn't put enough in,
B the compressor is dying,

I didn't wanna let on to anyone on this, but the mf is noisy when it's on.

A/C is fairly simple in idea. I'm bored and I'll give you a very basic rundown. (or anyone else who comes across this thread later)

The refrigerant is compressed by the compressor and it is changed from a low pressure gas to a high pressure gas, then it is run to the condenser where it will maintain the high pressure, but become a high pressure liquid. This phase change is very important. You want the pressure high enough that the temperature increases above the outside air temperature. That way the air blowing through the condenser will actually reduce the temperature and actually subcools the refrigerant. Then you should have a lower temperature, but high pressure liquid that goes to your orifice tube/expansion valve.

That is basically just a nozzle. When the high pressure liquid passes through the orifice tube it will have another phase change back into a low pressure gas. When that happens it drops temperature by a fairly large margin. That gas is evaporating and obviously that happens inside the evaporator. So now you have a low pressure gas that runs back to the compressor. and the cycle starts all over again.

Now the part of this that applies to you is that if you have too much refrigerant in the system then the high head pressure will elevate the temperature in the condenser too much and you are now sucking really hot air into your radiator and it loses it's effectiveness and the engine runs hot. The other likelihood is that you aren't passing enough air through the condenser and radiator and the condenser becomes "heat soaked" and will also not allow your radiator to work effectively.

Short story, you either have a fan clutch that failed/is failing or you have too much refrigerant in the system... I would probably make sure the fins are clean on everything too..

Edit: I didn't see your new post when while I was typing. The noisy compressor also makes me wonder about overcharging...

I usually prefer my low side pressure to be lower than factory when you do a conversion, some old low pressure switches were adjustable, or you can just buy a new one from a later model truck, they usually have a schrader valve behind the switch so you won't lose refrigerant when you change them.

Its clogged.
Runs fine until the clog catches , hampers flow, runs hot because the flow restricts through the condenser.
Right?

Is it bent at the driver corner?

Aint the orifice tube thing that little filter lookin deal they always tell you to change?
Why?
It's just a fvcking screen...might oughta try that again?
You can look at it without losing charge, right? I really dint know..
I do NOT know wtf im talking about AC.
Ahh too bad I didnt see that post first.∆∆∆
,That sounds very reasonable. I think we were typing at the same time yo.

Markmx6 said:

A/C is fairly simple in idea. I'm bored and I'll give you a very basic rundown. (or anyone else who comes across this thread later)

The refrigerant is compressed by the compressor and it is changed from a low pressure gas to a high pressure gas, then it is run to the condenser where it will maintain the high pressure, but become a high pressure liquid. This phase change is very important. You want the pressure high enough that the temperature increases above the outside air temperature. That way the air blowing through the condenser will actually reduce the temperature and actually subcools the refrigerant. Then you should have a lower temperature, but high pressure liquid that goes to your orifice tube/expansion valve.

That is basically just a nozzle. When the high pressure liquid passes through the orifice tube it will have another phase change back into a low pressure gas. When that happens it drops temperature by a fairly large margin. That gas is evaporating and obviously that happens inside the evaporator. So now you have a low pressure gas that runs back to the compressor. and the cycle starts all over again.

Now the part of this that applies to you is that if you have too much refrigerant in the system then the high head pressure will elevate the temperature in the condenser too much and you are now sucking really hot air into your radiator and it loses it's effectiveness and the engine runs hot. The other likelihood is that you aren't passing enough air through the condenser and radiator and the condenser becomes "heat soaked" and will also not allow your radiator to work effectively.

Short story, you either have a fan clutch that failed/is failing or you have too much refrigerant in the system... I would probably make sure the fins are clean on everything too..

Click to expand...

Excellent! I appreciate the run down.
My buddy that does residential HVAC for a living, he gave me the run down on how home AC works, admitted he didn't really know how the truck AC works, but told me things like a new air dryer, orifice, and compressor oil and all was needed.

Like I said, as I was putting the last can of freon on (not that **** you just pump in, actual freon) the compressor engaged, and never quit afterwards. I feel I either don't have enough now, or just enough. I don't think I have a condition of too much.

So it sounds like it's a cooling problem then.

Rusty Nail said:

Its clogged.
Runs fine until the clog catches , hampers flow, runs hot because the flow restricts through the condenser.
Right?

Is it bent at the driver corner?

Aint the orifice tube thing that little filter lookin deal they always tell you to change?
Why?
It's just a fvcking screen...might oughta try that again?
You can look at it without losing charge, right? I really dint know..
I do NOT know wtf im talking about AC.
Ahh too bad I didnt see that post first.
,That sounds very reasonable. I think we were typing at the same time yo.

Click to expand...

I understood if you didn't change that orifice tube, it'd really screw up the system.
When I did pull it out of the line, it was nasty. So I replaced it.

To clarify, I'm not an AC person, neither do claim to know anything. I just went by what a professional residential AC guy told me. The freon amount and pag oil amount I looked at via charts and the web.

What kinda pressure am I looking for on both low and high side, truck at temp, AC running?

I can report back this evening with those numbers, maybe that'll give someone a clue.

Vbb199 said:

Excellent! I appreciate the run down.
My buddy that does residential HVAC for a living, he gave me the run down on how home AC works, admitted he didn't really know how the truck AC works, but told me things like a new air dryer, orifice, and compressor oil and all was needed.

Like I said, as I was putting the last can of freon on (not that **** you just pump in, actual freon) the compressor engaged, and never quit afterwards. I feel I either don't have enough now, or just enough. I don't think I have a condition of too much.

So it sounds like it's a cooling problem then.

Click to expand...

They both work on the same principles, just different ways of doing it sometimes. I do commercial and industrial A/C as well. There are some things that are different though. I don't usually pull as deep of a vacuum on cars because of the rubber hoses. If they are new then you are fine, but as they get old you can cause them to leak by pulling a deep vacuum (which is measured in microns)

I do always recommend changing out the orifice for the above reason, but they are dirt cheap, so why go through everything else and wimp out on that. The accumulator/ receiver drier is also good to change because it helps keep moisture out of the system and since you don't pull down to a deep vacuum and use nitrogen to dry the system out you will always have moisture in the system.

For pressures, generally speaking I like to see around 30-40 PSI for the low side and the high side will also depend on your outside air temperature. If it is 100 degrees outside then you should be around 150 PSI. Also the low side will drop as the cab gets cooler too...

Here in Phx it isn't unusual to hit 118 degrees so my high side pressure may be around 210 PSI