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How warm at idle?

jed1154 on Tue June 17, 2008 5:20 PM User is offline

If the AC system is NOT on recirculate, meaning its bringing air from the outside, is it normal for the temp to get 65-70 out of the vents, idling with 95-100 degree ambient temps? That would be a 15 degree increase vs. driving.

comp on Tue June 17, 2008 5:31 PM User is offline

what system is it ???

brickmason on Tue June 17, 2008 6:35 PM User is offline

Of course it will raise the vent temp because your drawing warm outside air through the evaporator.

When everythings working correctly on recirculate as the interior is cooled then the vent temp will be lowered due to drawing cooled air across the evaporator.

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Chick on Tue June 17, 2008 6:43 PM User is offlineView users profile

Could be normal with a mechanical fan that needs replacement, but more info on the vehicle is needed... Hope this helps..

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Freedoms just another word for nothing left to lose

jed1154 on Wed June 18, 2008 9:17 AM User is offline

I think its ok. When driving, the vents get to 42 with 104 ambient temps (according to the outside temp sensor)....thats with recirc of course. Without recirc, its still in teh 50's so i think everything is good.

comp on Wed June 18, 2008 1:26 PM User is offline

run it the same (sitting) then add fans in front of the grill see what happens

jed1154 on Thu June 19, 2008 11:03 AM User is offline

i may try that. Ive only noticed it when its set to 'outside air'. You can go from 58 degrees driving to 65 degrees sitting still, unless you set it to recirculate.

TRB on Thu June 19, 2008 11:39 AM User is offlineView users profile

I don't see where the issue is at in this post. 42 degree vent temp when all buttoned up with a 100 degree ambient. 65 degree vent temp idling pulling in 100 degree ambient air. Personally I would be looking for a different project to be working on!

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jed1154 on Thu June 19, 2008 12:03 PM User is offline

there is no issue...im just asking because it will go to 70 degrees when pulling in 85-90 degree outside air as well. It doesnt fluctuate, it goes to there and stays. Its a diesel engine, so i guess its just that hot under there. It drips on teh outside, so its not freezing up. I just like to have outside air on to keep the air fresh, but in 80 degrees or warmer, it just can't keep up if im idling. If im driving, i can get the outside air down quite cold...45-50.

Edited: Thu June 19, 2008 at 2:28 PM by jed1154

jed1154 on Thu June 19, 2008 9:26 PM User is offline

How can the AC cool the OUTSIDE air to 50 while moving, but not manage to drop it more than 10 degrees when sitting still?

Edited: Thu June 19, 2008 at 9:27 PM by jed1154

Chick on Thu June 19, 2008 10:13 PM User is offlineView users profile

If you have an engine driven fan, check the fan clutch..It's obviously cooling when moving which would indicate a possible air flow problem..Just my opinion...

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

bearing01 on Thu June 19, 2008 10:32 PM User is offline

Quote
Originally posted by: jed1154
How can the AC cool the OUTSIDE air to 50 while moving, but not manage to drop it more than 10 degrees when sitting still?

At idle there's much less passing through the condenser, removing heat. High side pressures go up and if you got an orfice tube system that could cause slight overfeed of refrigerant to the evaporator, causing evaporator pressure to go up. When it goes up, so does the temperature of the air coming out of it.

My wife's car (1997 VW Cabrio, 4-cyl) has a variable displacement compressor (Sanden SD7V16). Once my RPM's go above 1500rpm the evaporator pressure holds steady at the 28psig set point and the air temperature out of the evaporator is in the 40'F range . At a stop light / idle the suction (evaporator) pressure rises to 38psig and the air blows around 50'F. It is a TXV system. I believe it's because the compressor (and the system) is designed to operate well at cruising speeds above 1500rpm. Also, bringing up the suction pressure at idle reduces compressor load on the engine. My other car (6-cyl engine) also has a variable displacement compressor holds the evaporator at 28psig rock steady no matter what driving condition. Always sharply cold.

[correction] I looked at my notes and my SD7V16 sucks 38psig at idle.

Edited: Fri June 20, 2008 at 10:37 AM by bearing01

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