A/C Occasionaly Turns Warm

[Duplex Dave]

Got My '97 last Nov. The A/C always blows nice and cold, strong. Recently in the 100 deg. weather 2 weeks ago the A/C just started blowing warm. I switched the intake to fresh air and it slowly went back to normal. I figured it was the extreme heat.
Yesterday it started doing the same thing only it was about 80-85 degrees. So, could a line be freezing up? Should I run it on fresh air all the time? Anyone else have this happen?
It normally blows very cold compared to my T-100 so I think the refridgerant should be good.

 

[Brentbba]

Not positive, but recall reading that our 80's have what basically amounts to a kill switch on the A/C if the engine gets to hot. It might just be that.

 

[1973Guppie]

I would keep an eye on what your actual car temps are (not the guage) when it happens. This will tell you if it is the ac kill switch or not. If you find the ac is cutting out under extreme engine temps then you need to look at your cooling system. Most likely the fan clutch is having problems. I had the same issue on my 80 with the ac cutting off in extreme heat. Got a landtank blue fan clutch and has never happened again. Good luck.

 

[Duplex Dave]

Brent and Noah, thank you for the great info. Ths newbie still has a lot to learn about our amazing vehicles...
I'm a little suspicious regarding the cooling system. The first time I took off the radiator cap there was a lot of pressurein the line, the wierd thing is it had not runfor 3 days? I took it in for a bunch of general tune up work and the mecanic told me someone had bypassed the transmission radiator? So I had them put it all bac to the stock set up. This is not my daily driver. Is there an aftermaket temp gauge I can install to see what's really going on?

 

[landcruising]

Given someone bypassed the transmission that makes me think you may have radiator clogs and they bypassed to keep the engine cool. You should start by checking actual engine temps with either a scanguage or you can by a phone app $5 and bluetooth OBD2 adapter from ebay for $10 to check temps. Of course this require a smart phone. I believe AC temp sender will shut it down when coolant hits 225 degrees.

1. Do you have green or red coolant, if green you may have sludge build up from mixing. ( this was my situation, the red was probably not flushed correctly when converted and the 2 don't mix well)

2. If your radiator is original it probably needs replacing. (Mine did due to number 1.)

3. it could also be the expansion valve in the evaporator under the dash. (Mine was bad along with the compressor and condenser $700 in parts)

4. As Noah mentioned a blue fan clutch adds more resistance than original and when modified with heavier oil means even air flow when at lower speeds and idle thus reducing engine temp.