air conditioning

[jyeager]

My A/C works fine when moving down the road at a nice clip, but is quite unacceptable when stopped or driving stop and go.

Obviously this is due to insufficient air flow through the condenser. Is it Nissan's engineering shortcoming or is something in the system not operating properly in my '97?

 

Unless a previous owner removed it, there is no electric fan to push or pull air through the condenser when the A/C is on. The mechanical clutch fan seems to do fine at keeping the engine cool, but doesn't do the trick for A/C.

 

Is this the case with all of you? Or is there something wrong with my truck? If this is normal, has anyone installed an auxiliary fan and found improvement?

 

 

[Rebelord]

Um, shouldnt be an issue. You have something else going one. If you have a proper pressure gauge set. Check your pressure for low side and high side.

Report that then we can go from there.

[adamzan]

If it's really hot out and you have the air on it should sound like a dump truck with the fan clutch. If it doesn't you might have an issue there. Or the pressure is too low like ^ said.

[NovaPath]

Yup, as they said either A. low on Freon, or B. mechanical fan clutch is not "clutching" any longer.

[5523Pathfinder]

Make sure your condenser in front of the radiator isn't blocked up with mud, dirt, debris and such. Tonight I just washed a bunch of mud out of mine.

[jyeager]

Thanks guys, I will check those things.

I do have a manifold/gauge and can check pressures.

 

However, the talk about the fan clutch...that clutch only engages when it's hot enough. Do you think that 80+ degrees F, is hot enough to lock the clutch? (obviously not)

Sure, once the truck is HOT, but when first starting it up it won't be.

So it seems as though you would agree that the A/C won't work well upon initial startup for a few minutes then, if idling or stop n go? (that seems reasonable)

 

You might be right about my fan clutch....However, my engine never overheats in stop and go traffic. But that's based on watching the temperature gauge which is probably designed like most others in that it stays in the middle until it's WAY hot, then moves up.

 

I can easily test the fan clutch, but at what ambient temperature is it supposed to lock up?

 

[NovaPath]

The clutch on mine only "locks" when it is significantly hot our and I am either idling for long periods of time or am moving and stop and go traffic(I live around the DC area so stop and go traffic is severe).

 

If it is not cold at first start up while idling, I suspect you are low on freon.

 

Good Luck!

[jyeager]

I will check the Freon (haven't yet due to busy weekend). But I did check the fan clutch.

I drove an errand in 95 degree temps, ended the drive in stop and go surface streets, then idled in park for 5 minutes. All of this with the AC on.

Then I shut off the truck, opened the hood and the fan spun freely.

 

Seems like an obvious situation in which the clutch should have been locked. Agreed?

 

[Kingman]

Agreed. Should be locked up tight with those temps and sound like a school bus.

[MY1PATH]

Don't over do it if you test the AC pressure. Too much pressure in the AC will also make it not as cold. PO on my 93 over charged it and when we moved to the desert I let about 20psi out of it and it started blowing cold in 110F weather.
Also test your Idle up solenoid, It should be kicking up your idle when the AC is running so that the compressor spins at the appropriate minimum speed to keep you cool.
I think If your idle is dipping below 900 with the compressor running that could be your problem.

Edited June 23, 2015 by MY1PATH

[jyeager]

Don't over do it if you test the AC pressure. Too much pressure in the AC will also make it not as cold. PO on my 93 over charged it and when we moved to the desert I let about 20psi out of it and it started blowing cold in 110F weather.

Also test your Idle up solenoid, It should be kicking up your idle when the AC is running so that the compressor spins at the appropriate minimum speed to keep you cool.

I think If your idle is dipping below 900 with the compressor running that could be your problem.

 

 

Thanks for that advice. I will make sure that my pressures are within factory specs. The service manual lists expected pressures at given ambient temperature ranges.

 

Are you saying that even when stopped with the transmission in DRIVE, my idle speed with the AC on should be raised at least to 900? Or without the load of the transmission in gear?

I will have to test that. I can't say that I notice the idle speed when I turn the A/C on and off, so perhaps that's not working.

 

Thanks.

[NovaPath]

For what it's worth I checked the resistance of mine after a similar driving situation, and even though I could audibly tell it was locked it still spun easily by hand with the engine off.

[MY1PATH]

If you really want your compressor to pump try putting it in P or N and holding the throttle to 1,100 - 1,500 rpm while you are waiting in traffic. This usually gets our work trucks to cool down a little sooner for us while we are loading up.

[jyeager]

For what it's worth I checked the resistance of mine after a similar driving situation, and even though I could audibly tell it was locked it still spun easily by hand with the engine off.

Hmmm.

 

That confuses me then. How to tell if it's locked or not? The sound of the fan the only way then?

FWIW, I have NEVER heard fan noise from my truck.

[MY1PATH]

A properly working fan clutch will always have free movement when the engine is off. "full lock up" to "unlocked" is actually a ratio of 80% to 20% pulley speed as controlled by a thermal clutch.
Usually when they fail they completely lock up for real and rob you of lots of power under acceleration. I've replaced a several like that in various cars over the years but I have never had to replace one for not being able to cool the engine.