DOUG @ ECS

Most of us high HP guys have had an issue or two with their C6's running hot in the summer, I have seen bone stock C6Z's overheat in traffic with the AC on when it's over 90*'s out, so after adding power and an intercooler in the way it only gets worse. If not overheat, at least to the point where it shuts the AC off.

It has been discussed here many times, but I don't think I have seen anyone post a little discovery we found recently so I hope this helps some of you.

Many people have posted their findings with the fan module wiring harness connection burning up, the easy fix is to just hard wire the connection there and that fixes it. Great, but the car still runs warmer then we would like to see even when it's not burnt up, and usually cannot sit in traffic with the AC on when it's really hot out. Naturally when you want the AC the most.

So being that we have been installing the Haltech ECU's in several of our higher HP builds, we recently removed the factory fan module on one of these cars and controlled the fans from the Haltech ECU. This particular car already had an aftermarket radiator and Dewitts dual fan upgrade, but still ran warm when not moving. Not overheating, but warmer then it should, plus once it got warm it had a hard time getting back down to temp unless you were moving fast. And forget using the AC when it's really warm out. Everything was in perfect working order, no burnt harness or wiring, and functioned as per OEM should.

We had contemplated huge modifications to the cooling system to combat the car running warm, but luckily we tried the rewiring first. We installed two separate HD weather pack relays for each fan with a good connection to the battery for a strong flow of juice, let the Haltech control the relays-but you can come up with a sensor switch and mount it in the rear of the right cylinder head if you dont have an aftermarket ECU, and the difference on the fan output was incredible. Noticeably louder and much more airflow then going threw the factory wiring, even when we jumpered the fan module to go to 100% output.

This is tough to know exactly what the fans are putting out because it's not like they have an RPM gauge on them, and honestly I cant believe it took us this long to figure out such a basic thing, but I never thought the factory wiring would hold back the fans that much so we never looked into this before. We just assumed the layout of the radiator/condenser and intercooler was the root cause, but it's not.

Doing this completely changed the cooling characteristics of this car, it's stays so cool now that we had to raise the fan temps from where we first put them. A complete night and day difference.

So hopefully that helps some of you get rid of your cooling issues that have plagued the C6 from day one, stock or high HP.

5 Liter Eater

After burning up the connector and then a few PW modulators I wired a relay triggered by the fuel pump fuse directoy to the fan. So engine running = fan running. It's a little ghetto but I did notice better cooling. Now that I have two fans I have both those relays running the same way. Screw messing with trying to pulse width modulate fans.

Unreal

Doug, sounds like a great opportunity to make a fan wiring upgrade kit. I would buy one.

1SwtRide

Great discovery Doug / ECS!

edge04

Wiring was the issue on my SC 71 camaro with ls. What I did there was install a dccontrolc.com controller. This ran my fans and electric water pump on its own stand alone ECU and temp sensor. This fixed my issues, same concept as above. I just bought a HHP C6 and will keep an eye out for hot temps this summer.

DOUG @ ECS

Thanks but I cant right now, we are so backed up with the demand for the C7 kit that we are literally working 7 days a week, 12-14 hrs a day. The CNC machine is almost running 24 hrs a day. Good problem to have, but I have several other new parts I would like to get to market too but just cant right now.

That said, you don't need me, you can order what you need from Summit or Jegs and take care of this. We used two of the relays and HD fuse holders from our fuel system wiring. The good weather pack relays with the thick wiring to them, not the cheapy ones, same with the fuse holder or they will melt in time like the old MSD BAP's did.
Order a fan switch that mounts in the head that will create a ground at the preset temp you ordered, and wire it in. Put the relay turn on power to an ignition wire, fuel pump hot would work well, and main power right to the battery terminal on the outside fuse block. Run the power wire to the fan or fans, and ground the other side. Done

If you have two fans you need two relays and fuses, each fan draws over 25 amps each!


Thank yourself John, it was you who wanted the fan/water pump switch wired in a while ago that made me realise how much stronger the fans ran when maxing out the fan module. Then when you remove the fan module all together, it really stepped up the fans, but the switch set that thought process in motion.

I honestly feel stupid for not finding this sooner, the car has been out for how long??

Also, with the dual fan option from Dewitts, I would say you need to upgrade your alternator like you and Lee did to the Billet Tech alternator. We can get them pretty quickly, and they do work well. Being that the twin fans draw over 25 amps each, your drawing roughly 55 amps from the fans alone at idle, add everything else in the car and I do not see a stock alternator keeping up with that.

DSteck

If the switching frequency of the PWM trigger out of the ECM is low enough, you can just run that into a SSR (one per fan) and retain PWM control.

Unreal

One concern about running a switch off the head would be the fans don't shut off when moving. I thought you wanted the fans off when the car moves past ~40 or so.

DOUG @ ECS

GM wants the fans off over 45 to warranty less fans, same reason why they use a module. I want the car to run cool and if I have to replace a fan once in the life of the car because of it, I'll get over it.

DOUG @ ECS

Good point, very possibly. I didn't look into other options since we used the Haltech on the first two cars we are doing this with.

Slo-Poc

Thanks for sharing, I might get this done while the car is in a 1000 pieces.

383

SSR? Whats that?

NSANEC6

I would also... cooling issues have been the bane of my existence...

narfdanarf

solid state relay

NSANEC6

Doug,

I have installed baffling in the nose, upgraded my alternator, installed the Dewitts with the Dual fan unit, replaced my plug module and heat sinked and insulated it the best we could.

My car is finished up at this point. How hard would it be to make this mod from this point in the build? Just curious if it would be worth another delay and the expense to get it done. Your results seem to suggest it is a pretty simple fix.

DSteck

njfl

Thanks for the tip Doug. I have dual SPALs in my 69 also and I always wondered why they were so much louder than the dual SPALs in my 05. I'll be doing this mod in the Spring.

LTstewy8

I discovered this on my C5 last week when the factory wiring to my SPAL fan lost its ground somehow. I made a quick fix by tying the fan ground to the framerail, and it seems to be spinning louder/faster with just that change. I am planning on running new wiring exactly like you mentioned to the battery fuse box terminal, except I will use the factory wiring harness to trigger the relay. That way the PCM will still control the fan settings like stock, and there is no need for another temp sender in the passenger head.

OliverM5

There must be some huge resistance in the stock fan wiring, hence the reason why so many "burn up" the stock connectors due to heat caused by this resistance....

DOUG @ ECS

Whoever takes the time to utilise the stock wiring to control the fans first, post up a diagram or some pictures to help others.

If I happen too I will, but I don't have any stock PCM cars scheduled for this anytime soon that I know of.