No cold at idle....
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Logistics Pro
Joined: Jul 2002
Posts: 4,821
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From: South Dakota
No cold at idle....
Hey guys,
My truck seems to have developed a A/C problem, and I'm pretty sure it's vaccum related.
It's been pretty warm here lately (103F and 85% humidity...) and I can only get the AC to blow lukewarm at idle. Give the motor some revs, and the AC becomes frosty in a hurry.
The system has the proper charge, belts are good, engine fans works right and cooling system is up to snuff, and the compressor runs like it should. Truck only has 58,000 miles on it.
Which leads me to think I have a vaccum leak somewhere. Is there a place on the Superduties that have a known problem with vaccum leaks?
Any opinions on what my next course of action should be?
TIA!
My truck seems to have developed a A/C problem, and I'm pretty sure it's vaccum related.
It's been pretty warm here lately (103F and 85% humidity...) and I can only get the AC to blow lukewarm at idle. Give the motor some revs, and the AC becomes frosty in a hurry.
The system has the proper charge, belts are good, engine fans works right and cooling system is up to snuff, and the compressor runs like it should. Truck only has 58,000 miles on it.
Which leads me to think I have a vaccum leak somewhere. Is there a place on the Superduties that have a known problem with vaccum leaks?
Any opinions on what my next course of action should be?
TIA!
Elder User
Joined: Sep 2004
Posts: 824
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From: Helotes, Texas
A lot of diesels have a problem with the a/c at idle. I always thought it was the low rpm's that caused it. The compressor is not running as fast, therefore the suction pressure is higher; and the condenser is not as efficient due to lack of air flow which causes higher discharge pressures. Both of these combine to drasticly reduce system performance. You may still have a vacuum problem as well. You can also install a valve in the heater core line that will help some too.
Max
Max
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Joined: Nov 2003
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From: Near DC
Not sure if this would help ease your mind or confirm that I have the same problem.
Mine has been the same as your's since day one. Even after it was serviced and tested after a worn through hose.
What does it do after you've run the roads for awhile then sit at idle?
Mine will stay frosty.
Mine has been the same as your's since day one. Even after it was serviced and tested after a worn through hose.
What does it do after you've run the roads for awhile then sit at idle?
Mine will stay frosty.
Thread Starter
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Logistics Pro
Joined: Jul 2002
Posts: 4,821
Likes: 19
From: South Dakota
Originally Posted by Max1775
A lot of diesels have a problem with the a/c at idle. I always thought it was the low rpm's that caused it. The compressor is not running as fast, therefore the suction pressure is higher; and the condenser is not as efficient due to lack of air flow which causes higher discharge pressures. Both of these combine to drasticly reduce system performance. You may still have a vacuum problem as well. You can also install a valve in the heater core line that will help some too.
Max
Max
I'll have to give the valve idea a look at.
Freshman User
Joined: Jun 2005
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Yes it is the low idle
chevy has the same prob with the 6.2 and 6.5 even with the heater/defrost i dont know about the duramax never worked on one and wont for quite some time. Hell my 7.3 is the first i have worked on sure i changed oil and routine maint but we never had a prob like we did the others including cummings
chevy has the same prob with the 6.2 and 6.5 even with the heater/defrost i dont know about the duramax never worked on one and wont for quite some time. Hell my 7.3 is the first i have worked on sure i changed oil and routine maint but we never had a prob like we did the others including cummings
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Posting Guru
Joined: Nov 2003
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From: Near DC
You can switch the door operations while at the max blower setting, you should hear it thump closed.
Also run the heater conntrols though their paces, see if they appear to be shutting off.
Another option is the hot water shut off valve from the core.
It sounds like a blend problem because it doesn't do it at higher RPMs.
I'm starting to think that it's losing vacuum that's holding the doors in their proper place.
There is a vacuum module behind the radio that it hooks up to, if you possibly can, measure the vacuum.
Also run the heater conntrols though their paces, see if they appear to be shutting off.
Another option is the hot water shut off valve from the core.
It sounds like a blend problem because it doesn't do it at higher RPMs.
I'm starting to think that it's losing vacuum that's holding the doors in their proper place.
There is a vacuum module behind the radio that it hooks up to, if you possibly can, measure the vacuum.
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Fleet Mechanic
Joined: Nov 2004
Posts: 1,427
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From: Templeton, Massachussetts
low rpm and the fact that the condensor is hot and cannot get proper air flow from the engines fan till higher rpm.
we test a/c performance @ 2000rpm.
and you need proper airflow.
we test a/c performance @ 2000rpm.
and you need proper airflow.