I have what is odd behavior lately from my cooling fans. I have HPTuners and in the Scanner application I can click on the low speed fan icon, by itself, and the drivers side fan runs at low speed. I can click on the high speed fan, again by itself, and the passenger side fan starts in high speed.

Here's the odd behavior... when I click on the low speed fan, wait for it to start, and then click on the high speed fan, the high speed fan kicks on, but the low speed fan turns off - even when commanded to run by HPTuners.

The reason why I'm even looking at this is because my car just recently started to run hotter than normal. I'm looking at the schematic and while the high speed fan *can* run independently of the low speed fan via the COOLFAN2 relay, it seems like the only way the low speed fan would stop if the high speed is running (and both are commanded to run) is if the A11 pin of COOLFAN3 relay has lost its ground.

What I'm looking for is a backup to either validate what I'm thinking, or correct my errant thought process -- and more importantly, how can I fix it so when the high speed fan runs, the low speed fan is also running.

For background information, I have verified this behavior on the car when running and hot, so it's not just in HPTuners.

 

In OE form, both fans operate together. They either both run in low speed, or both in high speed. Never independently of one another.

 

Yes, check relay 44 or the ground wire to it.

 

Thanks guys!!

I went out to do more investigation after posting my question. I tested relay 44 and by using a VOM and a 9vdc battery, and the relay is fine. So I checked the ground that A11 is supposed to provide, and it wasn't grounded. I opened the box and that's just too much work to figure out how I would work with all those wires to fix a single ground, so I unplugged relay 44 and ran a ground wire between the associated relay pin and to the negative of the battery. It WORKS

Not the clean solution, I know, but I think trying to actually use the wiring harness might get me into trouble.

 

Ground point G102 is located on the top of the right side frame rail, immediately behind the headlight assembly. Inspect it and clean as necessary. Use your DVOM to check for continuity between there and the relay plug-in location in the fuse box. There are several ground wires (for other functions) that all come together on the ground stud at that location, so you may have to probe each cavity, etc to determine which one is the ground your're looking for. If you have a poor connection at that ground location for the fan(s), you may also have poor connections for other components that ground there as well.

Don't "Jake Leg" things with some lashed up "fix". Do it right.

HTH

 

Right side is the passenger side? I'll take a look at it. Thanks.

 

Correct. "Right" side and "Left" side is/are ALWAYS based on the presumption of sitting in the driver's seat looking forward.

BTW, check the stickies. There's a good post by Bill Curlee regarding grounds in general, complete with pictures of badly corroded ground points and some cautions regarding stud breakage, etc. Folks living in Northern climates tend to suffer this fate more, due to road salts, etc.