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2001 Rodeo LOW side high at idle

Rodeoguy on Sun June 09, 2013 8:10 AM User is offline

Year: 2001
Make: Isuzu
Model: Rodeo
Engine Size: v6
Refrigerant Type: 134a
Ambient Temp: 80
Pressure Low: 65
Pressure High: 150
Country of Origin: United States

History- replaced ac comp (used), replaced accumulator, condenser and exp valve (all new). Cleaned/flushed all lines etc and evacuated. Held vacuum overnight.
Replaced 134a (2.5lbs according to sticker on car).
Problem-at idle, low side reads high until engine RPMs 1500-2000 and it drops to approx. 30-40 lbs. Cold air at vents (and while driving ..60degrees +/- ) Slow down or idle, temp jumps , almost no cooling at vent. Everything (to me) points to low refrigerant but I know I put in 2 full cans. Charts indicate an open exp valve, but this is brand new. I hate to break into the system again if its not necessary. This is a stretch-can refrigerant be defective (I also purchased that over the internet at a much better price than at Autozone (Dupont 134a).
Thanks for any help in advance...

Dougflas on Sun June 09, 2013 10:06 AM User is offline

You did all that work and purchased a used compressor????? 2 1/2 lbs of refrigerant equals 40oz. Is that what you out in?

94RX-7 on Sun June 09, 2013 10:22 AM User is offline

Originally posted by: Rodeoguy

Replaced 134a (2.5lbs according to sticker on car).

I put in 2 full cans.

This is a stretch-can refrigerant be defective

If you put in 2 12oz cans then you're well under the 2.5lbs called for by the sticker.

Refrigerant can be "defective" I've read about 30 pound cylinders coming from China that weren't pure R-134a. Don't know if there has been a similar problem with the little cans or not.

Rodeoguy on Fri June 14, 2013 11:29 PM User is offline

Sorry, my mistake...It calls for 1.57 lbs. I installed 2 (12oz) cans. I am going to evac the system tomorrow and try to refill with 2 fresh cans of 134. Am I correct in the fact that if the compressor works at 2000 rpm on the suction side, it is ok and I should look toward the expansion valve? Note, while driving today (approx. 90 degrees outside) the inside temp never dropped below 70.

mk378 on Fri June 14, 2013 11:40 PM User is offline

Did you tape up the TXV sensor properly on the evap outlet line (as it looks like it is not a block TXV)? Set the interioir fan to low, or even unplug it so there is no airflow over evaporator-- TXV should close down causing low side to drop-- if it does that the TXV is doing what it should-- thus then look to the compressor. I agree with Dougflas your used unit may be tired. Another way to test compressor is to kill the condenser airflow-- high side pressure should rise into the 400's. Be ready to shut it down or turn the condenser fans back on.

Edited: Fri June 14, 2013 at 11:42 PM by mk378

Rodeoguy on Sat June 15, 2013 8:26 AM User is offline

Yes, the expansion valve( located inside the evaporator under dash) is taped and the bulb was reinstalled in the original location. I am running the test you suggested right now. ( yeah, it was a stupid bet to replace the comp with a used one, took a chance, money was short, I burned myself). Thank so far for all the input...

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