2006 cooling fans

[Boog]

2006 GMC 5.3
all stock truck
OE dual electric fans

I noticed today the fans do not turn on unless the a/c is turned on. And they blow somewhat slow it seems. The truck has never overheated but I am curious why the fans don't come on with the a/c off. With it fully warmed it runs at 210*.
I am wondering how are these fans setup? Primary and secondary fans? Single or two speeds? How does one go about testing the fans and switches on this 2006?
In comparison my 2009 Yukon's fans blow like crazy.

[AussieinNC]

I have a 2006 5.3 Silverado...all stock...its my parts getter and daily driver...

Same scenario as you describe...fans come on immediately when AC is On....

Turn AC off and they will cycle on a hot day when stationary, but usually shut down at highway speeds...

Mine runs 210 Summer, Winter...AC On or Off...

[Boog]

I guess its safe to assume it requires a dealers scanner to test the fans and relays? I am curious if mine have 1 or 2 speeds and what the fans cycle points are.

[95 S_Trucker]

Originally Posted by Boog

I guess its safe to assume it requires a dealers scanner to test the fans and relays? I am curious if mine have 1 or 2 speeds and what the fans cycle points are.

Any decent independent shop will be able to look at it and verify it's working properly.

Has it overheated in the summer when sitting in traffic? If it ain't broke don't fix it.

[Boog]

As i said the fans run full time with ac on but at a slow speed. I have never seen them run any faster. Hence the ? 1 or 2 speed. Also sitting at idle ac off and temp at 210 no fans. So what is the cycle on point? It has gotten up to 235 or so when towing up a good grade but always cooled back down once over it. I just expect the fans to blow stronger than they do when the temp gets up there.

[95 S_Trucker]

Originally Posted by Boog

As i said the fans run full time with ac on but at a slow speed. I have never seen them run any faster. Hence the ? 1 or 2 speed. Also sitting at idle ac off and temp at 210 no fans. So what is the cycle on point? It has gotten up to 235 or so when towing up a good grade but always cooled back down once over it. I just expect the fans to blow stronger than they do when the temp gets up there.

The fans only job is to pull air through the radiator when traveling less than 35MPH, Or when the A/C is turned on.

When it goes up to 235 when towing up a grade, are you going faster than 35? If you are, the fan has nothing to do with the temperature increase.

The low speed should come on when coolant temperature is at 202. I can not find a spec for high speed.

What are you using to read engine temperature. Are you using a scan tool? An infrared thermometer? An inaccurate dash gauge?

The important thing is the truck isn't overheating when sitting still. You can tell the fan is effective.

[homemade87]

My 06 does the same . I rarely hear the high speed fan come on . Only time they do is I am running highway speeds w/ ac on and a quick shut down and start back up in a few minutes when the engine has time to build some heat and its above 95 outside . High speed will run a few minutes . Fans will only runs the minimum time preset when triggered in the ecm .

The low speed fans run in parallel and are hard to hear if at all . They are most likely cycling on and off sitting still .

[95 S_Trucker]

Originally Posted by Boog

As i said the fans run full time with ac on but at a slow speed. I have never seen them run any faster. Hence the ? 1 or 2 speed. Also sitting at idle ac off and temp at 210 no fans. So what is the cycle on point? It has gotten up to 235 or so when towing up a good grade but always cooled back down once over it. I just expect the fans to blow stronger than they do when the temp gets up there.

What are you using to measure engine temperature?

[Boog]

Just the gauge. Of course its not totally accurate but I’m not buying an IR gun to find out.
Homemade. Mines so quiet I have to raise the hood to see that they are running. I have never heard them running fast. Therein is the reason for my questions.
What I was looking for are the factory programing for the fans as in cycle on and off points and whether they are 1 or 2 speed fans and how one might go about testing his fans, relays to see if all is working as designed. Thats all. I felt sure someone here had tested theirs before.
Thanks all.

[homemade87]

The best and easiest way is a tech2 to cycle them . The wires to the pcm for fan 1 and 2 are green and blue in the relay fan harness . These wire are a ground trigger . Grounding these requires taking things apart .

The fans are a single speed fan . The low speed puts both fans in parallel , basically running each fan on 6v for 1/2 speed . The 3 relay system will switch to 12v to each fan ( high speed ) or parallel for low speed 6v . Depends what the pcm is calling for .

It sounds like your system is working just fine . I do not have the factory temp setting but I do know it is somewhere around 220 on and 195 off for low speed . I would think the high speed would be somewhere about 235 on and 225 off . If this is close this is the reason you are not seeing your high fan come on . Your system is working in the perimeters of the low speed settings.

[Boog]

That’s what I’m looking for. Those numbers sound reasonable. The truck has only shown appx 235 a few times when towing the 5th wheel up some slow grades during 90 plus temps. It cooled back down once over. I turned off the ac which gave it a bit more power. Thanks Homemade.

[68Gold/white]

The temp that the fans turn "on" at is higher than you'd think. I don't remember the exact number...My 05 temp gauge runs 210 all day long. The fans coming on with AC is normal.

Your 09 may be the next generation different deal...many things changed when the 07's came out...

As other have said, if it's not overheating, just keep driving it!!! Your towing temps sound normal also...

[dragonball98312]

My 07 classic is the same way. I’ve never seen them on or heard them. Tho 210 all day never hotter. Non ac truck