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High side too high

derby98 on Thu October 02, 2008 8:01 PM User is offline

Year: 99
Make: Nissan
Model: Quest
Engine Size: 3.3
Refrigerant Type: 134a
Ambient Temp: 70
Pressure Low: 47
Pressure High: 320
Country of Origin: United States

We have a 99 Nissan Quest / Mercury Villager V6. had a bad compressor. We added new compressor, Accum, orfice tube & flushed the system.
Added 3.5 lbs of 134a (has rear air ) we have 45/320 at idle. We recovered & charged again because we thought it was a possible overcharge. Same thing.
We suspected condensor was plugged so we replaced condensor & rechecked the discharge line for restrictions & found none. Evacuated system & added just 2 LBS of refrigerant & had 40/250 & vent temp was still warm. added 1/2 lb more & head pressure went to 50/330.

Any suggestions?

Chick on Thu October 02, 2008 8:09 PM User is offlineView users profile

Are you pulling a deep vacuum and charging into the vacuum? Is the condenser fan coming on when the AC is on?? What did the old O tube look like when you pulled it out? Also, did you flush thru the rear expansion device or remove it?

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

derby98 on Thu October 02, 2008 8:47 PM User is offline

yes always pull a deep vacuum everytime. we flushed the rear lines & changed rear exp' valve.
Condensor fan is coming on when clutch engages.
The O tube was not bad at all. NO black death in system.

I just had the vehicle running at idle 45/300 & i sprayed water on condensor & readings shot down to 30/180.

Readings back up after water is off

Chick on Thu October 02, 2008 9:19 PM User is offlineView users profile

I can't remember if that has one fan or two..If two, both should run when the AC is on..If one, that should also be on with the AC..Does it have multi speed fan, or just one speed? Spraying a mist of water brings the high side down, indicates an air flow problem.. Make sure the radiator and condenser are clean, including the area between them. Also make sure the fan is running in the right direction.. Pulling air thru, not pushing it out.. Did you use plenty of shop air to blow the flush out:? what kind of flush did you use?Does the pressures change much with the rear air off?

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

derby98 on Fri October 03, 2008 11:16 AM User is offline

The head pressures only go up a very little when you turn on rear a/c. One fan & it is on. 2 speed fan & it does come on hi when HP gets to 350 psi. It is blowing the right way.
The condensor is new & has new side foam seals. We did blow out the flush completely.
Right now ambient: 59. Ac on high blower 32/190. I know as the day goes on and ambient gets to 75 the HP will start to rise as It did yesterday.

I guess the radiator core might be clogged. The veh' had 176,000 miles. I will remove radiator & check core.

mk378 on Fri October 03, 2008 12:21 PM User is offline

The fan should be shifting to high somewhere in the 200's of psi. 350 is too high.

derby98 on Fri October 03, 2008 2:46 PM User is offline

The high fan seems to kick in at 350 psi. Possible bad fan switch?

derby98 on Fri October 03, 2008 2:47 PM User is offline

Does anyone have the specs on when the high speed fan should kick in?

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