Another A/C Problem thread

[SS Performance]

The A/C in the truck works sometimes. On initial startup it works. It works when I am driving. However if I get into traffic (stop and go) it stops working. Also if I stop for gas or at a store it doesn't work on starting the truck. Normally if I can drive several miles it starts working again.

I have concluded that not enough air is passing thru the condenser. I think there is a problem with the pusher fan mounted to the condenser. When the motor is on the fan is turning but slowly, I thing the air being pulled past it by the engine fan is causing it to turn. With the engine off and the ignition and A/C on it doesn't turn. My question is should this fan run continuously when the A/C is turned on or is it on some type of switch (such as a temperature or pressure switch) that turns it on and off as needed?

Thank you
Craig

 

[pressureangle]

Not much to go on, but start with what year and engine.
What have you for fan and shroud on the engine side?
I have 2 '94s, a 5.7 and a 6.5TD. The gas motor truck, even with a heavy duty fan clutch and big fan from a '05 Envoy will drop out when idling in very hot traffic. The diesel is ice cold all the time. The only difference is the condenser; the gas motor has a generic 4 seasons or some other whatever brand condenser, and the diesel has an expensive condenser from Classic Air. I believe that a lot of low-speed A/C problems are simply insufficient condensers. But you have to move air across them in any case.
An Auxilliary electric fan should be running any time your A/C is on, although in a simple system it will run when you don't need it to at speed. '94-up have a switch in the condenser line to activate the fan via solenoid when condenser pressure gets high enough.

 

[SS Performance]

Thanks for the reply. Sorry for lack of information.

1996 C3500 CC LB DRW with the 7.4L auto trans.

 

[L31MaxExpress]

Does your 454 have the spin on fan clutch? if It does, I would get an 04ish Duramax fan and 2007 Trailblazer SS thermal fan clutch. That sucker will move air when needed. My ac stays about 55°F at idle in my Express with a slightly trimmed Duramax fan.

 

[pressureangle]

Does your 454 have the spin on fan clutch? if It does, I would get an 04ish Duramax fan and 2007 Trailblazer SS thermal fan clutch. That sucker will move air when needed. My ac stays about 55°F at idle in my Express with a slightly trimmed Duramax fan.

Is that the electrically activated one? Was looking at one in the junkyard yesterday, for the diesel. I see 4 wires- what's it take to connect it properly?

 

[L31MaxExpress]

Is that the electrically activated one? Was looking at one in the junkyard yesterday, for the diesel. I see 4 wires- what's it take to connect it properly?

No the one I mention is actually the thermal version they make for it. Hayden 2851 or equivalent. Your PCM lacks the ability to fully control the electric version.

 

[kolgeirr]

The A/C performance at idle in my Suburban improved significantly after I installed a parallel flow condenser, a heavier duty fan clutch, and a variable orifice tube.

I plan to update the Tahoe similarly. The A/C in my Tahoe just blew a seal on Thursday, so I'll be throwing a full new system it in while it's got no charge. Going to use a heavy duty clutch and a later 11-blade composite fan, a parallel flow condenser, variable orifice tube, and Sanden-style compressor this go-around. Hoping that brings the idle temp down a few degrees at least.

Neither has the extra pusher fan, though I think I was skimming the manual the other day and it mentioned that the electric fan circuit doesn't tie into the A/C system at all and runs off a head-mounted temperature sensor. As a result it likely only responds to engine temperature and doesn't even know if the A/C is running or not.

I've also noticed that the idle cooling performance suffers before the at-RPM does when the refrigerant charge starts getting low. Might be worth checking your charge.

 

[GoToGuy]

When say , " doesn't work, sometimes", or " stop's after a while" . Those are non specific terms. Which you understand as you have the truck in front you and in your mind those terms are defined.
The problem is what does " stopped " define to the rest of world?
No fan in AC, AC no longer chilled air, compressor stops cycling, AC air cool not cold.
What exactly is happening defines where to go. The world beyond your post is blind.