1990 Toyota P/U A/C

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Old 06-17-04, 08:15 PM
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1990 Toyota P/U A/C

1990 Toyota P/U 4 Cyl FI A/C (R-12) started blowing semi-cool air and that only when moving. Figured it was a little low and brought it to A/C guy, who properly checked with gauges and agreed I was a bit low. So here we are, me watching him begin to add R-12 and dye with the proper equipment. He had just pointed out that it was "running high" (appx 50 PSI) when what he later called the expansion valve released with a brief "PSSSSSST!" At this point, he unhooked all equipment, unplugged the compressor, and said he would call me with a price, all the while leaving me more or less in the dark about exactly what was up.

I'm wondering if anyone could give me a heads-up on what may be going on here. Is it possible that a clogged evaporator core could be the culprit? Something else? It is my understanding that an expansion valve acts as more or less a relief valve for excess pressure release. Please advise if I am wrong. Needless to say, I intend to have my A/C fixed, but I would prefer to have a bit of knowledge about what is going on and this chap is rather tight with his smarts. Many thanks for any opinions or replies.
 
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Old 06-18-04, 02:42 AM
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No, The expansion valve for that vehicle is not even visible. It's under the dash. That is not the job of the valve anyway. You make be referring to the high pressure blow off valve. You say 50lbs, that would be the suction side. What was the high side? It sounds like he may have overcharged the system. He may be assuming the expansion valve is clogged or not working, preventing circulation and, in turn, cold air. Condinually adding freon would lead to high pressure blow off. Turn on the A/C while feeling the small line going into the firewall. That line should get warm. If you don't feel it getting warm right away, that indicates no refrigerant travel and a probable blockage. Could be drier or expansion. Should change both in that case.
 
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Old 06-18-04, 03:17 AM
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The expansion valve is the point where the high pressure become "low pressure".

Think of it as a controlled "sprayer". It restricts the freon as it flows into the evaporator and thats when the freon has the ability to remove heat. And that feels cold to use.
 
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Old 06-18-04, 06:49 PM
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Thanks for the reply, good people. Desi, that 50 psi reading was the high side or at least that is what the chap advised. the freon was being added with a monitering or scale type device (i say that because he set the tank on what appeared to be a scale that had numerical buttons on it that he seemed to punch a code or amount into). It was maybe a minute into the procedure when he said the high side was reading high, showed me the reading, and then that particular valve did its thing. (sorry not clear enough) Any idea of what a fair estimate I should expect for a valve and dryer change? Seems it may be a doozy, removing dashboard and such. SE LA area

Thanks again for the invaluable advice, good people. Wonderful forum.
 
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Old 06-19-04, 02:36 AM
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No, that reading couldn't be the high side. It would take close to 400lb to cause that valve to spit. The ambient pressure alone would be much higher than that. That has to be the suction side.
It's really not that hard to change the expansion valve in a Toyota. The whole job with the recharge, drier and everything will probably be around $400-$600. This is only a guess on that diagnosis and a knowledgable tech needs to determine if in fact, that's what's happening.
 

Last edited by Desi501; 06-19-04 at 03:50 AM.
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Old 06-19-04, 11:16 AM
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Thumbs up

Desi, the input is greatly appreciated. The price quoted was in that range. I'll be having a couple different shops check it (test it, ...), compare diagnoses & prices and go from there (hoping all diags are same ) With the advice and info provided by you guys, I can dig a little better what these people may be telling me next week. I'll be posting the outcome. Thanks a bunch
 
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Old 06-21-04, 05:55 PM
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All diags are coinciding with the last two prices running in the same ballpark (unlike the first chap, who wanted an ungodly amount) so I'll be getting it tended to later in the week.

One question, though.

The more reputable (and informative) shop keeps trying to sway me into "converting" from 12 to 134 by changing the oil in my compressor, as well as the dryer and valve replacement, and, of course, charging w/ 134.

From what I've read, most of you guys frown on this deal. Although I intend to stay with 12 at this point, even at the absurd price, I would appreciate any comments on whether this would be beneficial or catastrophic.

Thanks.
 
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Old 06-22-04, 03:19 AM
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Although R134 is a good refrigerant, it requires some differences in the engineering of the system. It usually works better with a larger condenser and barrier hoses. Putting R134 into a system engineered for R12 is rolling the dice at best. If it contacts any of the oil from the 12, the oil turns to jelly and this can be a problem, depending where it happens. The reason they are trying to talk you out of it is because the don't keep any around any more. The hassle and the price make it easier for them to sell everybody the R134. Once you have repaired your leak, the cost difference is not that serious and the system will be much more reliable in the future.
 
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Old 06-22-04, 03:40 AM
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Desi, thank you for your advice. This forum has been most helpful - I'll continue to read it on a daily basis just to learn. It will be the first place I come to if I have a more than basic (in my eyes) problem with either my Yota or my Intrepid.
 
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Old 06-22-04, 03:34 PM
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In my opinion 50 psi on the low side is a bit high for a restriction in the high side and will not ever cause the pressure to blow off on the high side at 50 psi.I would recover the refrigerant from the system and start from ground zero with an accurate charge of r-12.Sounds to me like there may be something else in the system like air or a refrigerant mixture r-12 and something else.Did this bozo have 2 hoses hooked to your a/c system or is he a lo side pumper upper?Maybe the compressor is leaking internally causing the high side to bleed pressure to the low side.Which would mean your system is not even low.If this vehicle uses a fan clutch which I'm sure it does it may not be functioning properly.Heed my advice before you dump the money in it.Call around and have it recovered by someone who can tell how much they took out of the system so you know if it's overcharged.Post back with results.
 
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Old 06-22-04, 05:06 PM
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I'm assuming it was overcharged, mostly because he kept adding, trying to get cold air until it blew off. Probably didn't have a high side connected either.
 
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Old 06-22-04, 07:04 PM
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I can safely say that hoses were hooked up to both ports on the compressor during the filling procedure and that the chap was monitering the gauges, as well as the scale-type apparatus that the 12 tank was sitting on. It wasn't just a hook up on one side (I've seen that) and holler "Let me know when it blows cold, hoss" thing.

Not takin' up for the dude, just trying to take you guys to the scene.

Thanks... your pondering is appreciated!
 
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Old 07-06-04, 05:53 PM
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Expansion valve and dryer changed, as well as this little Lego-looking gizmo (pressure switch, maybe?) attached to the expansion valve, which showed an obvious leak where attached. All is cool, real cool

Thanks again, good people. The invaluable info provided on this forum allowed me to hold a knowledgable conversation with these folks without them having to draw pictures in the dirt on my behalf.
 
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