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A/C blows cold (sort of) but does not cycle

MrMGA on Mon May 05, 2008 4:00 PM User is offline

Year: 1995
Make: Isuzu
Model: Rodeo
Engine Size: 3.2L
Refrigerant Type: R-134a
Ambient Temp: 85
Pressure Low: 35
Pressure High: ?
Country of Origin: Japan

My Rodeo has 110,000 miles on it and all the original, never-serviced A/C parts. There is a very slow leak in the system; every spring I recharge it myself using the "id" kit. It usually takes one or two 13 oz. cans of R134. After this procedure, the A/C immediately blows much cooler air, but I think it should be colder. It is sufficient in ambient temperatures up to 90 degrees or so, but quickly loses effectiveness at 100 or 110 degrees (I live in the Phoenix area.) I've also noticed that the compressor does not seem to cycle on and off anymore. Could that be the cause of the problem? The fact that I do get a fair amount of cool air at all means the compressor must be stuck in the "on" position, right? How do I diagnose and fix the problem?

vdubspeed on Mon May 05, 2008 4:59 PM User is offlineView users profile

if it's anything like my car. It won't cycle unless it's filled properly. Once it's filled properly it will cool enough to tell the compressor to cycle on and off.

Find the leak.

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I

mk378 on Mon May 05, 2008 5:03 PM User is offline

Yes it would be best to find the leak. Then recover, fix leak, evacuate and recharge to specifications. After that you won't have to mess with it every year.

I suspect you are not getting the condenser performance that you used to because the fan clutch is worn out and there's 110K of dirt and bugs in the condenser. Measuring the high side while properly charged would tell.

MrMGA on Mon May 05, 2008 6:10 PM User is offline

Quote
Originally posted by: vdubspeed
if it's anything like my car. It won't cycle unless it's filled properly. Once it's filled properly it will cool enough to tell the compressor to cycle on and off.


Thanks for the quick reply!

I think it is filled properly, at least according to the gauge on the "id" recharge kit. The needle on the gauge is in the middle of the blue area, which appears to be around 35 lbs. The leak is very slow; in a year the gauge will read in the 20 to 25 lb. zone. This last time I used a special refrigerant that is supposed to "seal most common leaks." Maybe that will work?

TRB on Mon May 05, 2008 6:43 PM User is offlineView users profile

Those dial a charge tire pressure gauges are a very poor way to judge a systems performance!!!

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bohica2xo on Tue May 06, 2008 2:52 AM User is offline

Where to begin....

Repeated recharging without leak repairs, or oil replenishment. "It's only a small leak" Yeah, "only" 20+ ounces per year... How much oil is left in that system?

Charging without monitoring the high side pressure - the death kit move. Kills better & faster than Bruce Lee on caffeine...

Adding "sealer". Maybe it will just seal your leak. Maybe it will seal the expansion valve too. Play "00" on the Roulette wheel much?


Now the compressor no longer cycles. Is it worn out? Perhaps too much air in the system? No way to tell without high side pressures. The compressor could be fine, or it could be on it's last legs from running without enough oil, recharge after recharge.

Time to test the pressures. Both high side & low side, at the same time. Doors open, cabin fan on max. Test & record pressures both at idle & 2500 engine rpm .

The leak can be located either by using an electronic "sniffer" or by adding a couple of ounces of oil & a bit of dye.

B.



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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

MrMGA on Tue May 06, 2008 9:31 AM User is offline

Quote
Originally posted by: bohica2xo
Where to begin....

OK, I get the picture.

I'm capable of recharging the system using the kit I bought at Wal-Mart, but that's it. Time to take it in to a professional.

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