LS3 fans not coming on

Can anybody tell me what the indicated temperature is on their Digi Dash when the fans cut in?

I recently let the car come up to full temperature to test if everything was working and no pipes blew off.

My setup takes the reading for the Digi dash temperature from the heater loop and from it you see the thermostat open at around 84 degrees c.

The GM fan signal should come on at 97 degrees c but it didn't and so I stopped the engine when 100 degrees c was reached.

Any ideas?
 
First the blue with yellow wire has to be put into the master cell main connector.
That same wire is connected to the GM fan output.
If the fans aren't coming on it is possible that Infinity Box put the inverter on incorrectly. (I've seen that a few times)
You can disconnect the wire back at the GM fan connection and give it power with the ignition on and see if the fans come on. If they don't the inverter is wired wrong.
The inverter is usually located about 6" back from the master cell connector.
 
fans come on around 200* in the standard gm program.

another problem could be the gmpp wiring harness itself - i went through 4 wiring harness, all with significant electrical issues (dbw did not respond, ecu did not turn, fuel injectors did not have power)

what is your cooling fan wiring - does the blue wire from the gmpp harness go tot he fan (i.e., gmpp ecu controls fan off/on), do you have it hooked up to isis controller, etc..
 
I initially had a problem with the fans running constantly , that turned out to be a faulty inverter.

I've replaced the inverter but now as I said they dont work at all.

I'll do what Allan suggested and power it without the GM harness connected, great idea.

Thanks
 
Alex

With so many bad GM harnesses, did GM give you replacements? Wiring has kicked my posterior, so I would hate to think I would have to take it all out.

Tell me it ain't so!!!

:lipsrsealed:
 
I initially had a problem with the fans running constantly , that turned out to be a faulty inverter.

I've replaced the inverter but now as I said they dont work at all.

I'll do what Allan suggested and power it without the GM harness connected, great idea.

Thanks

test the master cell circuit it was on - if you don't use an inverter you will damage the master cell. possible that maybe because of faulty inverter the master cell itself was damaged.

Alex

With so many bad GM harnesses, did GM give you replacements? Wiring has kicked my posterior, so I would hate to think I would have to take it all out.

Tell me it ain't so!!!

:lipsrsealed:

yes, each time it was warrantied (fun fact - any gm dealer is able to do an over-the-counter warranty swap for gm racing parts, but they'll give ya hell about it)

the sad part is i caused my own problem because my first wiring harness was okay but I'd accidently cut my drive-by-wire cable (and those are 1 set of wires i ain't splicing back together!). So i replaced the harness and got bad harness after bad harness after bad harness.

And of course each time i replaced the harness I installed it thoroughly - loomed it up, taped it up, etc... - only to have to tear it apart because i figured what's the chance of getting another faulty harness :/
 
Make sure the inverter is in place when you give power to the circuit. If the fans don't come on try switching the non ground connections on the inverter. Every time that the fans didn't work it was because the power feed connection was put into the wrong side of the inverter.

I've never had a GM harness that didn't send out fan power. But keep in mind I've only installed 19 of them ;)
 
I'm about to power my system up, fingers and toes crossed. I too loomed it up etc hoping for success, first time......ya rightttttt!
 
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Yep applied power to the signal wire and it's not switching the power cell output on.
Thanks for the tip Allan I have a spare inverter I'll fit it over the weekend.

Dan good luck mate.
 

PeteB

GT40s Supporter
Yep applied power to the signal wire and it's not switching the power cell output on.
Thanks for the tip Allan I have a spare inverter I'll fit it over the weekend.

Dan good luck mate.

After you remove the inverter, try grounding the signal wire. If that doesn't work, you probably fried the circuit in the Mastercell. My harness didn't come with an inverter in the wire. I followed the instructions in the ISIS manual and it fried the circuit. I ended up just connecting the fans directly to the GM wiring harness and bypassed ISIS completely.
 
After you remove the inverter, try grounding the signal wire. If that doesn't work, you probably fried the circuit in the Mastercell. My harness didn't come with an inverter in the wire. I followed the instructions in the ISIS manual and it fried the circuit. I ended up just connecting the fans directly to the GM wiring harness and bypassed ISIS completely.

Pete, did you wire the AC system to control the fans as well? There's a discussion of fan operation strategies in the wiki here.
 

PeteB

GT40s Supporter
Pete, did you wire the AC system to control the fans as well? There's a discussion of fan operation strategies in the wiki here.

Yes. I've got the fan wiring running through the A/C trinary switch (with some relays), again bypassing ISIS.
 
Yep applied power to the signal wire and it's not switching the power cell output on.
Thanks for the tip Allan I have a spare inverter I'll fit it over the weekend.

Dan good luck mate.

hook that circuit to something simple like a horn and test it. if it doesn't turn it on you've buggered that circuit on the master and/or power cell, inverter won't help, it'll need to be repaired (if you want to use it).
 
Hey fellas, as far as these fans go what kind of signal is ISIS looking for to kick them on, a ground or power? What is this "inverter" some of you speak of? My system (older) is nothing like what's in the manual. I don't have a GM relay/fuse box. Everything is done as per the ISIS manual from the fans back to the engine harness at the back of the car where there is "fan relay primary" and "fan relay secondary". To me it seems these should be tapped into the PCM that will provide ground when temp is reached. Again, there is no relay box back here. Was wanting hear the fans spin up tonight and was tempted to put these relay wires to 12v but something told me not to do it, so I didn't.
 
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Just read that the master cell does require a ground trigger... so doesn't that mean I can simply splice into my PCM and be done? Not sure why a relay would be needed. Glad I didn't send 12v through it, Lol. Found out what an "inVert" is, too.
 
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Kenny - be very careful with how you wire your fans. Fuses are not replacements for relays. The Isis system has fused connections but in several cases (like the fan) they are using woefully inadequate wiring to carry the current these fans draw, at least that was the case on my system. If you’re not familiar with how to wire a car up find someone local who can review the wiring with you.
 
Thanks for the info, Cam. And sorry I missed your call the other day, (again, more great info) I've been gridlocked into a battle with QuickBooks/Taxes etc etc at work and it's been pretty much non-stop. That's what I love about having the SL-C... I am able to come home and disconnect from work. Pretty sure I have my fans sorted. I ended up finding the inverter I was told I didn't have, lol. I cut it out, connected my trigger wire to the ECU trigger (ground signal), ran a couple relays and now have 2 working fans that come on at 180 degrees. Not going to mess with wiring one to the AC, when the car gets to temp I want them both on regardless so I'm good to go! Guess I need to start my own build thread... started cutting on the chassis tonight, too.
 
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