A/C problem

[nukefission]

Truck in question is a '95. On a hot day, the A/C will work fine within the first ten minutes of starting up and driving. After that (when it gets hot, or when the engine gets loaded up a lot like from accelerating onto a highway), the A/C cuts out and doesn't blow cold anymore. I checked the low side pressure with a cheapo DIY refridgerant filler gauge and found that it was within the normal range when the compressor was engaged (whether it was blowing cold or not). Adding refridgerant did not seem to make a difference. Sometimes I can here a relay (I assume A/C clutch) clicking on and off rapidly, but those are random occurrences as far as I can tell.

I'll be taking it to a friend who's more experienced at A/C diagnosis than I am, but I wanted to get some input from here on whether there are any common component failures (relays, switches, etc) on these trucks that I should be aware of.

Thanks.

 

[fourwd1]

I've never had or heard of a switch or relay problem with the AC. The compressor clutch going bad is fairly common (happened on my Trooper), and the front seal on the compressor blew out on my 84 (higher pressure from the R134 conversion).

 

[fourwd1]

That's not to say a switch or relay won't go bad, it's just not a common problem.
(just to be clear)

 

[nukefission]

Thanks. I took it to my friend's and we narrowed it down to the expansion valve. We think there's some blockage there because the sight glass doesn't show much movement and the low side line sometimes pulls a vacuum. I got the valve from Advance and will be putting it in shortly. We'll see how it goes.

 

[nukefission]

Looks like the expansion valve was indeed the culprit. Replaced it and recharged the refridgerant, all is well now.

 

[nukefission]

Looks like I spoke too soon. Over the past few days the cooling capacity of the A/C has gone down. The fluid in the sight glass is a dark brown color but clear with no bubbles. I put more refrigerant in it, thinking some had leaked out. The new stuff contains UV dye that I had hoped would reveal the leak. So far, no leaks at the easily visible locations. Only place left to check is the evaporator...

 

[Hen_Feen1034]

Nuke did changing the Evaporator fix the problem? I'm having the same problem with my 95 4Runner and found this thread in a search.

Thanks!

 

[Hen_Feen1034]

Guess I'm kinda hijacking this thread but here's a small update...replaced the evaporator and expansion valve, tried recharging and the compressor clutch turned over once and that was it. Put an entire can in the low side without the clutch engaging, figured the expansion valve was installed incorrectly or I forgot to clip down the pressure switch or something, took everything apart again, obtained a new expansion valve but this time threw a vacuum on there. I was able to get a -12 vacuum but it only held about 10 minutes before it went to zero so I definitely have a leak.

I'll be adding leak detector tomorrow hoping the clutch will engage...more to come.

HEN FEEN