spideynut

I have a 94 4runner v6. A/C Blows cold most of the time but latley its been blowing worm for a few minutes then cold again. I checked the compresser its not turnig when warm. The green ac light is on. Ofcoarse compressor is on when its blowing cold with green a/c light on. Any tips on what to check next would be great. Brad

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93YotaGuy

Sounds like your expansion valve may be clogged or the condenser is not being sufficiently cooled.

Do you have the stock fan or an electric fan?

Has the AC system ever been serviced?

Have you ever replaced the expansion valve?

I would probably start by making sure that you have enough freon in there. Likely chances are that you may be low causing the compressor to run intermittently.

spideynut

Everything is stock. No i have never serviced it. Where is the expansion valve? If freon was low would it be so cold when its actully running?

93YotaGuy

You might want to service it.

Hopefully, the refrigerant will be low which causes it to work intermittent. Therefore the compressor would kick on after the system builds up enough pressure and then shuts off when the pressure is not sufficient.


The expansion valve is located underneath the glove box in the cooling unit. Sometimes when they get clogged the pressure builds up and when the pressure is sufficient it blows out of the expansion valve cooling the cooling unit.

Check out the FSM and try to diagnose the problem. If you have enough pressure in the system at all times then likely chances it is something else.

The system is not difficult to work with but it helps to have an idea as to how it works before you start messing with it. If you do decide to start taking it apart be sure to REMOVE THE FREON FROM THE SYSTEM. It is under pressure and the toxins will not only polute the air but will shoot out at you!

Good luck!

yodaLJ

Before you spend tons of money, check the simple things, most compressors have plugs on them, wiggle it and see if the clutch is kicking in and out. I had that problem with my peterbilt, I thought it was something a lot more serious, grabbed the plug one day checking the oil and found the problem. it only takes a couple minutes and could save you a lot of time.

spideynut

Will do guys. I've become spoiled with ac. When I was young I never used it windows where fine.
But now its 24/7 I never shut it off, morning ,day or night. And I work at 3am!

93YotaGuy

Yeah I hear you on that one.

Make sure you are maintaining what you use though. You wouldn't drive your truck for years with the same engine oil right?

In other words, don't neglect your system components and they will keep on working.

JBurt

So did it turn out to be the expansion valve?

spideynut

You know what it hasn't gotten hot since Feb. So still not sure. Been meaning to service it but little scared to mess with it since its workign fine.

wyoming9

These systems have both a high and low pressure switch that shut off the compressor.

It could be as simple as low pressure shutting off the compressor

A loose connection at either of these switches would also cause this issue.

Also if either of these switches is going bad it will do the same thing.

abecedarian

A partially blocked exp valve, or a low refrigerant charge could cause the pressure between the compressor and valve to rise faster than normal. You would get cold air for a moment, then the compressor would kick off until the pressure drops enough for the a/c amplifier to turn the compressor on again.

Were it the low pressure switch, the compressor would likely never turn on: that's a safety feature of sorts so the compressor doesn't run continuously if the system has too little or no refrigerant, which would then burn up the compressor.

Your's is a 94 so it should be HCFC-134a. You can likely pick up a recharge kit at O'Reilly's, Autozone, etc., and use that to put some in your system. DO NOT overcharge it. Likely, you only need 8 ounces or so, but only add as much as you need- no more. If the temp of the air coming from the vents is consistantly ~50F, you probably have enough refrigerant (give or take).

You should, however, take it in so someone with proper equipment can check for leaks.

gennro

Its the low pressure switch kicking it off at low rpms due to low refrigerent in the system.

abecedarian

It also could be low RPM's causing it to kick it off since the pressure depends on the speed of the compressor.

However, since it does kick on, there must be at least enough pressure and therefore enough refrigerant present to keep the low pressure switch from completely shutting down the system.

And that it does blow cold for at least a moment says there's refrigerant in the system.



And now I go off tangent: is the heater core being correctly blocked off by the valve so that no hot coolant flows through it?

spideynut

Not sure I can check. I did it the other day for the first time since feb. I was in the drive through a micky d's and sure enough went from freezing to warm. I immediately start hitting the ac button, sliding vent switchs etc.. but nothing. The drive through was all backed easy 15mins. Once we got back on the road 2-5mins it went right back to cold. Not sure coensidance or what but thats what happen.And cold ever since no drive throughs Brad