bt95formula

iTrader: (2)

My a/c will come on and run sometimes. It has been running and blowing cold then the air from vents gradually gets warm. Turn A/C off, wait a while turn back on and will work but does same thing over time. Cannot always repeat this. Sometimes I cannot get compressor to engage at all.

Things I have done are: check coolant level, replaced radiator(small crack), Check level again, replace wire and plug to coolant temp sensor (when you touched the wire/connector idle would drop, has since fixed that problem), fans are all working(sometimes will run at 1st start up of day, not sure why, maybe related) if I unplug the pressure sensor on a/c line, compressor usually kicks on, then turns off. Swapped relays around everything still works as should. I had system evac and refilled with dye and no leaks found yet. Pressures read
100 low side static
91 high side static
29-30 low side comp running
148-175 high side running (1st check 175 then checked again at home with same gauges 148, I think I had the valve open on both and let it equalize, low side shot up)
temp on dash guage 210 constant(I know, not accurate)

I have researched this for about 2 weeks now (bought car off of member here with blown motor and purchased long block from him and had him rebuild motor and install) A/c has not worked normally since purchase.

things I know I need to look at are the a/c pressure switch and coolant temp sensor. I hope I didn't miss anything. Sorry so long but could someone maybe point me in the right direction. Thanks

LS6427

iTrader: (2)

If you're having issues with the A/C pressure switch you need to fix it before worryiong about anything else. If its bad it will turn the compressor on and off randomly, which is directly the cause of the air suddenly blowing warm.

Fix it.

Coolant temp sensor has nothing to do with the A/C system.

bt95formula

iTrader: (2)

Is the pressure switch the cause of the problem? The reason I mentioned the coolant temp sensor was I thought I read in another post that if it is reading incorrectly (or correctly)it will trigger the fans which will in turn shut down the a/c? Is this correct?

LS6427

iTrader: (2)

It would be a first for me to know that the temp sensor or the fans can turn the A/C compressor on/off. But that pressure switch is there to do exactly that. It reads the pressure of the refridgerant in the system, when it gets low it shuts the compressor down so it doesn't burn up.

But yes, the coolant temp sensor can cause the fans to go on and off and freak out if its going bad. But as far as I know, it has no ties with the a/c compressor.

Change both.

bt95formula

iTrader: (2)

Thanks for the help. That was going to be my last resort but I will replace both to be sure. Thanks again

CamaroSS22

iTrader: (1)

be sure to check the expansion valve too, its a long shot but if the valve begins to open more then normal it will cause the high pressure side to drop and cause the low side to come up. I had the same problem with mine.

bt95formula

iTrader: (2)

Thanks for the advice. Someone at work had mentioned this as well.