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2006 chevy trailblazer_lt
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84 Posts
gotcha.. i may put one in regardless just for an added level of safety.. more or less protecting the pcm from my wiring.. i think i got it figured out tho.
 

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2002 chevy trailblazer_lt
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1 Posts
One question that is a variable input for the 5v source on fan clutch,was thinking about putting a resistor on that to fix the getting warm issue at idle. Instead of the Efan upgrade. Just a small fix till I decide what I'm gonna do pcmforless or just get fans and a switch :undecided
 

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2004 chevy trailblazer_ls
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3 Posts
Fan Bypass

My 2003 4.2L Trailblazer simply will not Tow a 3000lb RV in the summer without overheating, a towing weight well below the capacity of this vehicle. All cooling system components were replaced even though they appeared in mint condition for the age of my vehicle. I even replaced the entire Exhaust system and made sure the vehicle was in perfect condition otherwise.

Nothing worked period! It appears to be a badly engineered cooling system apparently relating to the PCM controlled fan clutch. The Fan Bypass is the only thing that allowed me to pull my small 3000 lb RV.

I installed a transmission cooler and followed the advice in this thread on the Fan Bypass. The Transmission cooler seemed do do nothing for cooling. However the Bypass was instant and absolutely solved the cooling problem!

So my advice if you're having the problem use the bypass option.
I know this is a very old thread but it helped me solve a problem and I thought I would add my 2 bits.
Thanks Nuttyskier2002
 

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2003 chevy trailblazer_ls
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25 Posts
My 2003 4.2L Trailblazer simply will not Tow a 3000lb RV in the summer without overheating, a towing weight well below the capacity of this vehicle. All cooling system components were replaced even though they appeared in mint condition for the age of my vehicle. I even replaced the entire Exhaust system and made sure the vehicle was in perfect condition otherwise.

Nothing worked period! It appears to be a badly engineered cooling system apparently relating to the PCM controlled fan clutch. The Fan Bypass is the only thing that allowed me to pull my small 3000 lb RV.

I installed a transmission cooler and followed the advice in this thread on the Fan Bypass. The Transmission cooler seemed do do nothing for cooling. However the Bypass was instant and absolutely solved the cooling problem!

So my advice if you're having the problem use the bypass option.
I know this is a very old thread but it helped me solve a problem and I thought I would add my 2 bits.
Thanks Nuttyskier2002
I also have a 2003 & that electronic fan clutch is a big joke. I just recently replaced it with a 2008 Trailblazer thermal fan clutch which is just like the fan clutch Chevy used for years. To eliminate the fan code errors I am sending my PCM to lime-swap.com & having it tuned at the same time.
WTH was GM thinking with that stupid fan clutch idea. My Trailblazer has so much more power now, temps are staying good and all in all it is a joy to drive now.
I have no idea how you fixed yours, but this is what was recomended to me.
 

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2004 chevy trailblazer_ls
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3 Posts
Fan Clutch

Interesting "Snoozer"
Just install a Fan clutch minus the electronic harness,never thought of that. Not sure how the PCM would try to compensate for that. Otherwise I would not care about the code. If you gained horsepower that would be nice even though I don't understand how it would. I'm actually losing power with the Fan Bypass switch (Simply a hot wire to the Fan that is switched on with a toggle when needed) But I like your solution. Might try it if I have any more trouble.
 

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2003 chevy trailblazer_ls
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25 Posts
Interesting "Snoozer"
Just install a Fan clutch minus the electronic harness,never thought of that. Not sure how the PCM would try to compensate for that. Otherwise I would not care about the code. If you gained horsepower that would be nice even though I don't understand how it would. I'm actually losing power with the Fan Bypass switch (Simply a hot wire to the Fan that is switched on with a toggle when needed) But I like your solution. Might try it if I have any more trouble.
All the PCM does without the electronic fan clutch is throw codes because it thinks the electronic fan clutch is not working right.

I have been running the 2008 fan clutch for about 3 weeks now both city & highway driving without outside temps around 100 degrees with no issues at all other then service soon light is on.
The guys over at GMTNation are the ones who suggested to go that way.
I think the increased power has come from the electronic fan clutch was going into fully engaged mode way to often & this was a new clutch that I had put on.

I am just glad to be done with this fan clutch issue & can move on to other things that I want to do the Trailblazer.
Makes me wonder what GM was thinking when designing this fan clutch & then deciding to go back to what has worked for many years.
I used to be a mechanic back in the 70's & 80's & I can not remember a time that I had to replace a fan clutch.
 

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2005 chevy trailblazer_ls
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70 Posts
I too was a mechanic in the 60s to the 80s when I wasn't on active duty, and I have found that sometimes good old fashion mechanical fan clutches work better with their simple barometric spring than a electronic clutch, with it's computer controlled switches which rely on sensors which can be influenced by defective electronics, poor design and trying to save a couple of bucks by the manufacturer. The electronics are getting better, I remember when Cadillac came out with their V8-6-4 engine, and right before I went back in on active duty, I must had replaced 8 or 9 of those engines with normal V8 engines, because the PCM could not keep up with actual road conditions like it could under controlled conditions, so the engines were extremely unreliable. But now, the technology has caught up, displacement on demand works good, and the benefits are great. So, maybe now, by this time, a electronic fan clutch would be a good ideal, but back in the early years of our Trailblazers, what worked good in the lab, didn't always work good under real world conditions.

Gene:)
 

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2002 chevy trailblazer_ltz
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19 Posts
I took the Thermostat out of the housing and my trailblazer runs cooler than the other side of the pillow.
 
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