Radiator fan runs when engine is cold

[swathdiver]

If the computer decides to, my electric fans run during remote start. GMT900s.

The conventional clutch fan on the 900s flows more air than two 700 watt electric fans. Don't recall how much anymore.

 

[Marky Dissod]

The conventional clutch fan on the 900s flows more air than two 700 watt electric fans.

Over as little as 1000 engine RpM, I'd be willing to bet that that's true.
If I were in the market for a GMT900, my only questions would be:
Does the mech fan flow more air than two OE electric fans AT ENGINE IDLE?
Is it enough for the AC to continue to perform well at idle even while stopped in traffic @ 45C / 113F outside?

Just noticed you said 'two 700 watt electric fans'.
Guessing those are NOT OE for GMT900s?

 

[swathdiver]

Over as little as 1000 engine RpM, I'd be willing to bet that that's true.
If I were in the market for a GMT900, my only questions would be:
Does the mech fan flow more air than two OE electric fans AT ENGINE IDLE?
Is it enough for the AC to continue to perform well at idle even while stopped in traffic @ 45C / 113F outside?

Just noticed you said 'two 700 watt electric fans'.
Guessing those are NOT OE for GMT900s?

Many GMT900s come factory equipped with 700 watt cooling fans. All three of my trucks have them.

I don't have a 2500 Suburban or Yukon XL, those have a mechanical clutch fan. Let's ask a few. @Derick @intheburbs @Moosemoon

 

[swathdiver]

Some more who might share their experiences:

@Jimmit @Shackman7878 @Nap73 @99bluefirebird @Oldmopars @t_bergman @tungsten @02Yukon2500 @S33k3r @Goober @DRayson @YukonBrian

 

[Fless]

If the computer decides to, my electric fans run during remote start. GMT900s.

The conventional clutch fan on the 900s flows more air than two 700 watt electric fans. Don't recall how much anymore.

The 900s come with clutch fans? I thought they were all electric for NNBS.

 

[swathdiver]

The 900s come with clutch fans? I thought they were all electric for NNBS.

The 2500 SUVs at least. The 6.0s in the HD pickups might have them too. Not sure what the Duramax's have.

 

[Derick]

The 2500 SUVs at least. The 6.0s in the HD pickups might have them too. Not sure what the Duramax's have.

Yup.. I do miss the jet engine take off under 30mph on a morning start. Kinda miss that noise. Sounded manly. 15 mph, 2nd gear driving through the neighborhood ... THRUSTERS AT FULL!!!

 

[tungsten]

Any 6.0 or Duramax Ive owned are clutch.

 

[Shackman7878]

Some more who might share their experiences:

@Jimmit @Shackman7878 @Nap73 @99bluefirebird @Oldmopars @t_bergman @tungsten @02Yukon2500 @S33k3r @Goober @DRayson @YukonBrian

I have a 09 Yukon XL (gmt900) was thinking about ditching the clutch fan but cant find a decent kit or write up that dose not involve reprogramming something after or having to new temp switch, or something you stick in the radiator. I noticed it sounds like a jet engine in the morning until the engine warms up.

Video on how much power it robs -

 

[mattbta]

Based on my preliminary experience with the e-fan conversion here are my thoughts, with more to come as we ramp into Texas summer:

Idle/low speed AC performance: Electric fans
Highway (55+) AC performance: Mechanical fan
Butt-o-meter (SOTP) go-fast: Electric fans

As I did the programming to turn the e-fans on, I know that I used to stock setting of 45MPH to turn the fans off, so it reasons that the highway performance is better with a spinning mech fan. Hopefully that's the case, or I'm facing more AC repairs. It used to freeze my face off. Now it's just "cool". I think I measured high 40's at the vent.

I still think I'm ok with this trade-off if it is legitimate, because idle/traffic speeds AC performance have always been less than desired. I'll report back when we get hotter and I drive it more...I'm still not driving much at all.

 

[intheburbs]

I've towed several different 4K lb campers in the Rocky Mountains (Denver to Western Slope, multiple high passes) for several years now and haven't needed the conversion to keep the engine cool. If the rest of your cooling system is good, the non-efan should work fine.

I tow an 8600-lb trailer with my Suburban. It's been through the Eisenhower Tunnel (11,000') and over Powder River Pass (9666') multiple times.

Parked at Wall Drug:

E-fans will NOT help when towing at highway speed. The primary benefit is better cooling at idle speeds, particularly in terms of the A/C performance. Someone who lives in the South and doesn't tow a lot? Probably a good candidate for an E-fan swap.

One of my customers is a Tier 1 supplier who makes mechanical fan clutches for cars and light-duty trucks. Yes, there was a big push to E-fans in the late 2000s. You know what the OEMs found out? E-fans suck for cooling under high loads.

Yes, the 2500s have mechanical fans. Because mechanical fans simply work better for heavier-duty applications. And the ONLY time I hear the "roar" is when I'm towing heavy in the summer. And rarely does the A/C go warm at idle.

My 09 Denali has the E-fans.

Underhood of my Suburban :

 

[Marky Dissod]

E-fans will NOT help when towing at highway speeds.

Certainly not nearly as much as a proper mech fan, when it comes to towing very heavy loads.
A proper mech fan is likely better than aftermarket high-wattage e-fans supported by major electrical upgrades.

Yes, there was a big push to E-fans in the late 2000s. You know what the OEMs found out?
E-fans suck for cooling under high loads.

The ever-increasing requirements represented by CAFE MpG targets started the big push to e-fans.
Vehicles that do not tow, or tow lightly, are better served by electrical fans.

Yes, the 2500s have mechanical fans. Because mechanical fans simply work better for heavier-duty applications.

Good thing 2500 and up are ignored by CAFE MpG testing - as they should be; they do most of the heavy towing.

 

[S33k3r]

Based on my preliminary experience with the e-fan conversion here are my thoughts, with more to come as we ramp into Texas summer:

Idle/low speed AC performance: Electric fans
Highway (55+) AC performance: Mechanical fan
Butt-o-meter (SOTP) go-fast: Electric fans

As I did the programming to turn the e-fans on, I know that I used to stock setting of 45MPH to turn the fans off, so it reasons that the highway performance is better with a spinning mech fan. Hopefully that's the case, or I'm facing more AC repairs. It used to freeze my face off. Now it's just "cool". I think I measured high 40's at the vent.

I still think I'm ok with this trade-off if it is legitimate, because idle/traffic speeds AC performance have always been less than desired. I'll report back when we get hotter and I drive it more...I'm still not driving much at all.

I read somewhere about a TSB -- not the TSB itself -- that indicated the addition of a small, electric fan to improve AC performance, while keeping the mechanical fan.

 

[S33k3r]

BTW, can confirm Duramax is mechanical fan.

 

[Marky Dissod]

I read somewhere about a TSB -- not the TSB itself -- that indicated the addition of a small, electric fan to improve AC performance, while keeping the mechanical fan.

That TSB:
Maintains mech fan's increased cooling ability over 1000 engine RpM for towing
Restores 'sufficient' AC functionality
Cheaper than pair o' electric fans conversion (that was unavailable before '05 a anyway).

Yeah, I see why GM did what they did the way they did it.

Too bad they did not also offer a 'pair of electric fans' conversion OPTION - but they'd've likely overcharged for that ...

 

[S33k3r]

That TSB:
Maintains mech fan's increased cooling ability over 1000 engine RpM for towing
Restores 'sufficient' AC functionality
Cheaper than pair o' electric fans conversion (that was unavailable before '05 a anyway).

Yeah, I see why GM did what they did the way they did it.

Too bad they did not also offer a 'pair of electric fans' conversion OPTION - but they'd've likely overcharged for that ...

Do you have a link to that TSB? I live in Texas, and have three vehicles that might benefit from it...

 

[Marky Dissod]

GM TSB #01-01-39-004A

01-01-39-004A Chevrolet Technical Service Bulletin

01-01-39-004A Chevrolet Technical Service Bulletin

www.tsbsearch.com

Abbreviated edited text is as follows in case the link fails in the future:

A/C Not Cold Enough, A/C Blows Warm Air with Vehicle at Extended Idle
(Install Auxiliary Electric Coolant Fan) - (Dec 20, 2002)

Models: GMT800 suvs & trucks with big ol' mech clutch fans
Please discard Corporate Bulletin Number 01-01-39-004 (Section 01 -- HVAC).

Condition
Some customers may comment that the A/C stops cooling and blows warm air when the vehicle is idling for an extended period of time such as sitting in traffic.
Cause
Inadequate airflow over the condenser may cause this condition.
Correction
The addition of an auxiliary fan in front of the condenser radiator assembly may help to alleviate this condition.
The coolant fan will come on each time the A/C compressor is commanded on by the PCM.
This fan will create a roaring sound when operating.

How To : Aux cooling fan/ condenser fan install with pics!

Ok guys, My first thread here is going to be a how-to after some info. I will begin the how-to in the next post. The story goes like this. I recently bought a clean 2002 Tahoe for hauling my kayaks and dogs and to keep the miles off my new Tundra. The air conditioning is cold while driving but...

www.tahoeyukonforum.com

 

[S33k3r]

Thank you!!!

 

[Marky Dissod]

If keeping the mech clutch fan is a requirement because the vehicle regularly hauls or tows very heavy, it would be a good idea to implement this TSB.
... or (rubs chin as an idea forms) ...
Add the TSB fan, but wire it up and program the tune so it behaves as the primary electrical fan.
In other words, instead of laying dormant unless the AC is demanded, it could behave as the primary fan would behave in any GMT800 that came equipped with a pair of electrical fans.
This might decrease the mech fan's duty cycle. I guess the question is, how much?
Feel free to rip on the idea, or complement it, as y'all see fit to do so.

 

[S33k3r]

I don't think it is the mechanical fan's duty cycle that is a problem; I think it is the shifts from engine speed to not engine speed (engaging the clutch) that wears it out. Also, the TSB indicates the fan makes roaring sounds when engaged. This would increase your loud factor with unpleasant sounds... So I think I'd prefer to see if I could get a quieter fan that would move as much air.