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97 Nissan Altima AC shuts off

mitchedo on Mon June 23, 2008 4:35 PM User is offlineView users profile

Year: 1997
Make: Nissan
Model: Altima
Engine Size: 2.2
Refrigerant Type: 134
Ambient Temp: ~95
Pressure Low: 36
Pressure High: 410

My buddy at work has this car and on a hot day (89 at the airport right now), the AC shuts off as soon as the engine comes to an idle after the car warms up. I went out and watched it for 20 minutes on the gauges (engine cold when we started). While the high side pressure was under 350 or so, we could drop it to idle and the AC would stay on. Then I watched the high side climb to about 410 and the compressor stayed on. As soon as he let it drop to idle (at 410 on the high side), the compressor shut off and will not come back on until the car cools off.

I didn't have my thermometer, but weather.com says it's 89 at the airport, and we aren't too far from the airport. It always seems to be a few degrees higher a few inches in front of a condenser.

The car has electric pull fans, both of which are working. I can feel a good rush of air right in front of the condenser. I don't see any obvious signs of condenser plugging, though there are a few bent fins at the bottom in both corners. I couldn't get the high side to come really high with the hood open, but once I closed the hood, it started its climb to 410. It would cap out at about 350 with the hood open.

Once we let it drop to idle at 410 on the high side, it wouldn't come back on for further testing. It seemed to peak at 410 with fast idle, but it did not shut off until the engine dropped to idle (at which time the high side did not go over 410). ...seems like an airflow over the condenser issue (electric fans, so idle shouldn't be an issue there), but why does it go off and stay off? Is it hitting the HPCO? I should say that at idle, the compressor would only pull about 60 on the low side with the high side at 350.

At idle the pressures equalized at 200 pretty quickly once the compressor shut off.

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Doug
Home of the "Tunex Suburban Disaster"

Edited: Mon June 23, 2008 at 4:36 PM by mitchedo

mk378 on Mon June 23, 2008 5:02 PM User is offline

Clearly that pressure is too high. Could be overcharged or have air in the system. Start with an evacuate and recharge by weight to be sure what you have.

The not coming back on when hot could be the clutch gap. It should come back on once the pressure drops. I think you're saying it will not engage at all even if you rev the engine. If it does engage when you rev the engine, the idle speed could be out of spec (too low) and the engine computer is killing the A/C to prevent stalling.

Chick on Mon June 23, 2008 5:45 PM User is offlineView users profile

Has he ever topped it off with refrigerant and sealers?

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

mitchedo on Mon June 23, 2008 6:59 PM User is offlineView users profile

It was acting a little low last year (just reduced cooling capacity), and he took it in and paid for some kind of service. I don't remember what he said they did, but they didn't replace any parts. The weather wasn't particularly hot when he had it serviced. This "shutting of when hot" started after that -- once the weather got good and hot last year.

As for it coming back on, once the car warms up and the AC shuts off, the AC clutch will not engage until the car cools off -- whether idling or racing. The odd thing is that it only shuts off once it drops to idle. I was thinking maybe once everything got hot, the clutch coil got weak.



-------------------------
Doug
Home of the "Tunex Suburban Disaster"

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