A/C Weirdness.....

[MrZero]

I'm at work and don't have my manuals, but I wanted to see if any of you guys had any thoughts about this off the top of your head. I posted a couple weeks ago about an AC conversion. I figured I was out of freon. This morning on the way to work, for whatever reason, I flipped on the AC. It blew COLD. Not just cool, but cold like it always has. Obviously I have freon and probably don't have a leak at any component. So what's failing? An electrical switch in the system somewhere? I'm going to look over the manuals tonight, but I was curious to see if you gurus could get me thinking in the right direction.

Thanks,

--ZERO

10/85 FJ60

 

[swank60]

I'd check the expansion valve. Not that I know how, mind you...

 

[Vortec62]

Sounds like loose wire type wierdness to me. My rig is an '88 FJ62 so the wiring may be a little different but...

I'd start by pulling the wire that goes to the compressor clutch and checking with your volt meter. It should come on when the A/C button is in and the fan is on. When I was checking my system out I got about 10 or 11 volts on this wire. If the clutch wire doesn't come on the next thing I'd check is the pressure switch.

On mine the pressure switch is wired into the A/C amplifier which was on the air ducts in front of the passenger seat. Mine was 2 yellow wires going into a multi-wire connector on either side of a blank spot in the connecter housing. I'd unplug harness from the amplifier and check the continuity of the pressure switch. If the system is low on refrigerent the pressure switch will open and there will be no continuity. When there is refrigerant there will be continuity and the compressor should turn on until it get up to xxxpsi and the pressure switch will open again and shut off the compressor.

Since you say your system blows cold when it does work I'd bet that mechanically everything is OK...the only moving part is the compressor. Intermittant problems are usually loose wires or faulty sensors. In this case it could be the clutch on the compressor too.

That's about what I know...Good Luck!!!

 

[hj60]

The expansion valve is a mechanical part, too.
And to check it, run the A/C and look for frost near the evaporator inlet.
That'd meant the TXV is stuck closed or nearly closed.
If it's stuck open, your compressor would likely not cycle off, IIRC.
I'm having a similar situation with my A/C in my apartment. Always works
fine when the maintenance men show up, though. :-\

 

[MrZero]

Well, I'm hoping it's something electrical or otherwise outside the closed system. R12 is EXPENSIVE.

--ZERO

 

[dd113]

If it is cold then stops being cold I bet it is freezing up. This is usually caused by crap in the filter/dryer. Usually it will blow cold a while then stop. Turn it off wait 15 min of driving then see if it will blow cold again. If so the interval between freezing and thawing will shorten and eventually it will just be frozen. Hook the gauges to it prior to turning the AC on then run it and see what the gauges say when it cuts off. You should see a hi side pressure change. I think it will go up but not 100% sure on that. The way to fix it is to replace the filter dryer and vac the system to get all the crap out then recharge.

 

[HZJ60 Guy]

What is AC?


TB

 

[hj60]

[quote author=HZJ60_Guy link=board=29;threadid=17484;start=msg169372#msg169372 date=1086398885]
What is AC?
[/quote]

Alternating Current.

 

[Mudshack]

[quote author=dd113 link=board=29;threadid=17484;start=msg169316#msg169316 date=1086391134]
If it is cold then stops being cold I bet it is freezing up. This is usually caused by crap in the filter/dryer. Usually it will blow cold a while then stop. Turn it off wait 15 min of driving then see if it will blow cold again. If so the interval between freezing and thawing will shorten and eventually it will just be frozen. Hook the gauges to it prior to turning the AC on then run it and see what the gauges say when it cuts off. You should see a hi side pressure change. I think it will go up but not 100% sure on that. The way to fix it is to replace the filter dryer and vac the system to get all the crap out then recharge.
[/quote]

I think that you are on to something. I live in Houston and my LX450 started doing the same thing last night. Ironic, since it was fine before taking it into the shop. But it runs great for about 5 min, and then nothing. Just damp air. Had a similar problem in an old apartment, and the lines were freezing up due to the lack of freon. This does not sound like a or job. Any advice?

 

[hj60]

There are EPA/legal issues with doing it yourself. If you vent any
refrigerant to atmosphere, you could be heavily fined. (Of course, that's
only if you get caught.) They do allow for you to work on your own
system, though.
But, that's not my point. My point is this: Before you do anything
expensive, of bring it to a shop, blow out your condenser. Get the leaves,
grass, insects, birds, McDonads bags, etc out from between the fins.
(Can't hurt to do the same fr your radiator and trans cooler while you're
there.) I can't believe I didn't think of that sooner. Airflow over the condenser is one of the most important elements of the A/C system in a
vehicle. And it's cheap.

 

[60wag]

Two thoughts on your AC issue:

The AC on my Acura Legend would occasionally stop working. I finally got into the evaporator box under the dash and found it full of pine needles and leaves. After cleaning them out, it worked fine. I think the junk in the evap core was restricting air flow and allowing the evap to either freeze up of get so cold that a temp sensor was shutting the system down.

The other possibility is that your idle speed is low enough that the AC amplifier (yea, the one with the blue knob) won't allow the system to come on. Try this: with truck idling, warmed up, turn on the AC and then look to see if the compressor is engaged. If its not, pull out the choke to speed up the engine to 1300 rpm or more, then check the compressor again. If speeding up the engine makes the AC work, then you can up the idle speed a bit or monkey with the blue knob to lower the turn-on threshold - probably a little of both so you don't have to suffer with the engine racing at idle.

 

[jhstatts]

Good to know about blowing out the condenser... I need to check that on mine.