ReneB64

Hey all,
depending your your past experiences. I have a 1993 toy 4x4 3vz and recently developed a problem with the ac. It runs very cold, and blows good, but after about 10 minutes it starts to blow warm air. If I turn it off for a while, it will sometimes work again, but it is hit and miss. I figure it is not freon since it blows cold in the begining. I found a troubleshooting guide, but the closest problem is refers to is intermittently having cold air. It says maybe magnetic clutch, expansion valve, moisture in system, or ac amplifier faulty. I was thinking maybe the AC cutoff relay, if not that then maybe the AC amplifier. Anyone have any experience with this? Where is the ac amplifier anyway, and what does it do?
Thanks

KellyKel

Hmmm. I would post up on the Auto AC Forum. These guys know AC.

http://www.autoacforum.com/categories.cfm?catid=2

ReneB64

Hey,
Thanks for the input, maybe I will get a few others with ideas.

abecedarian

If it's blowing warm air even when the compressor is running there could be a charge problem. In case of being too much undercharged, there is a circuit that detects this (the amplifier) and should shut the compressor off. It should also be able to detect a severe overcharge situation but may not in all cases and this could cause the compressor to lock up.

The amplifier is behind the dashboard, above the glove compartment, if I remember correctly and is there to monitor the evaporator temperature and refrigerant pressure and cycle the compressor on or off as necessary to maintain a consistant temperature as well as to turn on the a/c idle up valve so the engine idle rpm doesn't drop when the a/c is on.

Unless you've got experience working with A/C systems, take it to a shop. HFC-134a conversions are a bit temperamental and usually require more refrigerant to work at the same level as R-12, but it's a very fine line between not enough and too much due to the expansion valve / orifice not being designed for 134a and whether or not the compressor can cope with the higher pressures 134a requires.

ReneB64

Thanks,
So, it is possible it is the relay, or unlikely?

superjoe83

does the compressor ever cycle when the ac is on? if it blows really cold the compressor may not be cycling and the evaporator is freezing up.

ssupercoolss

if the compressor is running while it is blowing the warm air, check your valve that shuts the coolant off to the cab. make sure you dont have hot coolant going into the cab.