AC warm when idling - aux fan ok

[Semblance]

So my ac blows noticeably warmer at idle. Still a little cooler than ambient air, but not enough to deal with the latest heat wave. Cools off a lot when I get the car moving to about 40mph. I searched and found that the aux fan could be the cuprit, but I checked and mine is running fine at idle with ac on. The ac system will lose charge over time so I know I have a slow leak, but I just recharged it about a month ago.


Any other thoughts?

Oh, and it's nice and cold at idle when the engine is cold, but that's usually in the am when the air temp is also much lower, so I'm thinking it's maybe not related. But what do I know.

Any help appreciated...

[jlevie]

Could be a worn compressor or a bad expansion valve. Check system pressures when the charge is correct. Also if the system has been converted to 134a, overall performance will be down and that will be noticeable at idle. 134a needs a larger evaporator and condenser. You can't do anything about the evaporator, but a parallel flow condenser helps.

[Semblance]

ah, ok. yeah, PO converted to 134a. the whole system probably needs a once-over anyway.

thanks!

[702pjc]

Could be a worn compressor or a bad expansion valve. Check system pressures when the charge is correct. Also if the system has been converted to 134a, overall performance will be down and that will be noticeable at idle. 134a needs a larger evaporator and condenser. You can't do anything about the evaporator, but a parallel flow condenser helps.

Why is it that every time there is a thread regarding A/C temps people feel the need to call R134a systems inferior? There are just as many other posts of people claiming the same performance from R134a if you do a full conversion including a spal fan. So which is it?

[NeedaE30]

my old e36 m3 had r134a and that thing blew frigid artic winds

I've owned 3 e30's and never had a working r12 system so i cant compare but i see no reason to have anything blowing colder than what they do, when they are charged and working properly. whether it be r12 or r134a

Sorry i cant help you fix your a/c.

[vpilarrt]

I moved the AC diode output wire (black) (inside the fusebox) from pin 86 on K1 to pin 86 on K6 so that the Aux Fan runs on high when I turn on the AC. Helps with cooling the freon.

[Semblance]

If I understood Jim correctly, it's not that 134a is inherently inferior (I can tell you my e46 is FAR colder) - but that the e30 components such as evaporator and condenser aren't optimized for 134a so you don't get as much cold.

Thanks for the diode trick - but I hear it will blow cold without that if it's working properly. It blows cold enough when at speed, and when it's not 105 degrees out. So I'm thinking it just needs an overhaul. Hasn't been properly serviced in 10 years, and I know the compressor has a slow leak.

[jeffnhiscars]

Why is it that every time there is a thread regarding A/C temps people feel the need to call R134a systems inferior? There are just as many other posts of people claiming the same performance from R134a if you do a full conversion including a spal fan. So which is it?

The simple answer is "it depends". I have 2 converted cars with new updated (ie 134a designed) compressors and and I sold a converted car with an otherwise bone stock system with, I suspect, a swapped expansion valve and they all blew high 30s at the vents.

As Jim said, the biggest issue is design. An e30 compressor on r134a will never be as efficient as one designed for r134a largely due to the different head pressures. My theory is that if you get everything just right, which is as much art as science or luck, you can do well with minimal changes. If you want it reliable and predictable then you go the extra mile.

FWIW the easiest way to improve cooling at idle in any system is to jump the resistor and swap the low speed fuse for a 30a (and no it wont overload anything).