2nd Gen Non-Engine/Transmission Ice cold AC under load, warm air at idle?

[GBrock]

While under way, my AC blows ice cold. Once I come to a stop for more than a minute, it starts to loose the ability to cool and within 2 minutes warm air blows out. My diesel mech suggested perhaps I needed a charge of Rc 134. I tried that to no avail. Another non-diesel mechanic said it's my fan clutch going out. Sounds reasonable to me. Has anyone experienced this? Is replacing the fan clutch a costly fix?

 

[BILLVO]

Yes the fan clutch would be the most likely problem with the details you gave. Have you cleaned the condensor and radiator out also?It is easy to change the clutch but it takes a special wrench to remove it. Not sure the cost of a new one would guess about $75-$100 range.

 

[Joe Mc]

I don't think that R134a looses it's punch/ability to exchange heat - I could be wrong though. I think the problem is lack of air flow accross the condenser. I would clean the condenser coil first - then see what happens. If it were the clutch fan you would also be running hot - yes?

 

[BILLVO]

I don't think that R134a looses it's punch/ability to exchange heat - I could be wrong though. I think the problem is lack of air flow accross the condenser. I would clean the condenser coil first - then see what happens. If it were the clutch fan you would also be running hot - yes?

No r134a doesn't loose cooling ability,unless it leaks out :-laf .

No it would not run hot with a bad fan clutch, if these engines are not working they will not get to hot. I know of several people that have run with no fan at all for years with no problems. You manual transmission guys can get away with that. With auto transmission you need to keep it to keep oil cooler. But it also helps to cool down the condensor when idling. If you had gauges on the ac system the high pressure side will be very high due to low cooling effect of no air movement through condensor.

 

[JJPage]

You are most likely low on charge. R134a is a mixture of several different refrigerants, if you have a leak, (and they all do leak,with an open shaft compressor the seal will leak) the refrigerants will leak off at different rates, so you end up with a mixture that is different from R134a. The reason it is cooler when you are traveling is two fold, (1) you are moving more air across the condenser so it is removing more heat from the hot gas and doing a better job of condensing it back to liquid, (2) as your rpm increases your compressor spins faster, as it speeds up your low side pressure drops, pressure and temperature are relevent, the lower the pressure the colder the temperature. That is why a system low on charge will freeze the evaporator, the refrigerant freezes the condensate to the coil. Your best bet is to evacuate the system (pull into a 500 micron vacuum) and recharge to factory specs. It should be marked on the drier, lbs/oz.

Just my 2 cents.

 

[B.G. Smith]

Check and see if your vacuum pump is keeping up, could be no vacuum at idle and the blend door is opening. Should be above 17" at idle. bg

 

[dslmacdown]

You are most likely low on charge. R134a is a mixture of several different refrigerants, if you have a leak, (and they all do leak,with an open shaft compressor the seal will leak) the refrigerants will leak off at different rates, so you end up with a mixture that is different from R134a. The reason it is cooler when you are traveling is two fold, (1) you are moving more air across the condenser so it is removing more heat from the hot gas and doing a better job of condensing it back to liquid, (2) as your rpm increases your compressor spins faster, as it speeds up your low side pressure drops, pressure and temperature are relevent, the lower the pressure the colder the temperature. That is why a system low on charge will freeze the evaporator, the refrigerant freezes the condensate to the coil. Your best bet is to evacuate the system (pull into a 500 micron vacuum) and recharge to factory specs. It should be marked on the drier, lbs/oz.

Just my 2 cents.

R134a is not a blend! 134 is Tetrafluoroethane, a single pure chemical compound. R401, 404, 408, 409, 500, 502 and those type are blends.

 

[scotmartin]

dslmacdown is correct. It is the R-12 "drop-in" replacements such as 414a and 414b that will seperate under leaking conditions and must be completely replaced even if some of the charge still exists.



I had the same problem that the thread starter had with his truck. It turned out that it was my fan clutch. I was surprised that the engine temp was not affected.



Scot

 

[JJPage]

Sorry about the misinfo on R134a, I guess my 2 cents is only worth 1 cent.

 

[GBrock]

Yes the fan clutch would be the most likely problem with the details you gave. Have you cleaned the condensor and radiator out also?It is easy to change the clutch but it takes a special wrench to remove it. Not sure the cost of a new one would guess about $75-$100 range.

Turns out this was the fix... cleaning the condensor/ radiator out.



Thanks for all the help, guys.

 

[BILLVO]

Your welcome. That what its all about here. More often than not its the simple things that are overlooked the most.