FireInMe17

Can someone please explain the process the vehicle goes through to turn on the fans? I am having issues with mine, they will not turn on.

1990 Camaro with dual fans, I have tested the fans direct to battery and they both work, I got 12 volts to the wires in the relay, and replaced the relay to make sure it wasn't the issue, but still something isn't right, so scratching my head pretty hard right now? Can anyone shed some light on what the issue might be before I spend the money on a aftermarket fan controller? Thanks!

OrangeBird

iTrader: (1)

Looking at the schematic for your fans I see there are two relays , one for the main fan and one for the aux fan . Both relay's coils rely on grounding the ground side of the circuit for triggering . The relay for the main fan gets it's switched ground activation signal from the ECM . For that relay , it's the dark green/white wire that needs to be grounded to run the fan . The relay for the aux fan gets it's switched ground signal from both a sending unit looking switch that will be usually screwed into a cylinder head to monitor coolant temperature and activate if too hot , and/or the "Fan A/C Pressure Switch" , and it's switched ground wire will be grey .

PS , when you ground the dark green/white to test the main fan relay , if the relay runs the fan you can then look for an ECM problem . If you ground the grey for the aux fan and it runs you can check the temp sender (normally open till a certain temperature is reached , then closes , providing the ground side for the switched circuit) , and the A/C pressure switch . Also don't forget the key needs to be in the run position when testing the fans & relays .

Schematic info from Austin Third Gen , 1990 V8TPI ....

FireInMe17

Thanks orange, I'm going to tear into it tmrw and see what i can't find given what you've provided. I have the service book but it's not always as clear as written word! Haha

John in RI

iTrader: (167)

Hellava' response Orange; but I get the feeling it's gonna' get more complicated than stock wiring........

3.1 converted to a 355 Vortec TPI LT4


What kind of duel fans did you install ?? ( from what car, and what year ? )

What you are using to control the fans ??

FireInMe17

I used a factory wiring harness from a 1991 Trans Am, that so far has proven to be fully functional minus the fans. The dual fan set up is out of a 1991 Z28 that I got the chance to see run with it's stock TPI system before it was pulled and I got the fans and intake up and the bottom end went in a friends 84 Monte Carlo SS. Computer is an AC Delco replacement unit for a 7730 and the memcal is a custom G1 unit with Moates G1 adapter that was custom tuned by Scott Hansen who set the fan to kick on at 195* and shut off at 180*. Car has a 180* thermostat. Only thing in the engine bay that isn't supposed to be there are the 906 vortec heads and the GMPP LT4 hot cam that's also accounted for in the tuning. Car is no A/C, smog and egr delete that is also in the tune. I was under the impression that the secondary fan was turned on by the fan temp switch on the passenger side head, did not know about the A/C plug that obviously has no business being there with no A/C unit to speak for so that might be the issue with the secondary fan, but everything should be in place for the primary fan to work correctly as it should. I went over every inch of the harness before I installed it to check it for faults but there's always the possibility of something that I missed. So far I haven't heard the fan relay kick on to turn the primary fan on, so that could be an indication of where the problem is. Computer should be telling the fan to come on.My goal with the swap was to use all factory parts to get a cleaner than factory look...

FireInMe17

John in RI

iTrader: (167)

OrangeBird ----> Nailed it !!! Here Ya' go; ( from the 91 shop manual )


I'm not sure that the 3.1 and TPI fans were wired the same, so you might have to do some re-wiring to get the circuits to properly match-up. ( don't know if this was already done or not. )









I don't recall what temp the primary (ECM) controlled fan was supposed to kick on,... but the schematics show the factory secondary (HD) fan switch does kick on till 238 degrees and off @ 214.

Here is some info on lower temp switches for the secondary fan:

This fan switch turns ON @ 212 degrees & OFF @ 204 degrees:
Four Seasons 35946 (this is the GN sensor, GM OE # = 3053190)
(STANDARD MOTOR PRODUCTS Part # TS136 )


A couple others are:

TS85 - OFF @ 211 degrees
TS147 - OFF @ 222 degrees



I don't have info for the original 3.1 fan set-up, but no matter what it used to look like,... it needs to look like the schematics above if you want it to work like the TPI duel fan systems.

Not sure if these will help, but you can find the 91 C100 plug (firewall) and C207 plugs (dash-to-ECM)info for the 91 Camaro here:

http://berlinetta.info/tech.htm


Good Luck !

FireInMe17

Thanks guys, this will give me plenty to go play with for awhile and see if I can't get anything to happen. Maybe the problem is the fuse is not right in the fuse block. I'll have to get a diagram for the fuse block and see if its different.

I think it would be strange if that was the case though because so far everything in the MPFI V6 fuse block has matched up perfectly with the MPFI TPI V8...hmmm.

John in RI

iTrader: (167)

One more piece of info to help you figure it out ,....




I recall that the V6 and TPI had very similar wiring those years, and that the TBI wiring was very different then the fuel injected wiring.

Hope it works out for Ya' !

FireInMe17

I checked in my 1990 book, I jumpered the black/red with the orange wire on the relay and the primary fan comes on and works great. Keeping the car cool to ~160-170 degrees. Now my question is this, is there a different type of relay that these cars can use in the same location? The diagram on the relay shows it jumping together different wires than what it needs to work, maybe that's the problem?

FireInMe17

Same jumpering process works for the secondary fan...

John in RI

iTrader: (167)

A working fan when performing this test tells you 3-4 things.....

Fan has ground,
Fan works, ( & Black Red wire is OK )
The Fusible Link 'D' is OK.

That's about it. You haven't evaluated the relays in any way at this point.

To test the relay you need to jump the relay "switched" signal with ground. Dark Green/White stripe wire with the primary fan relay and Grey wire with the secondary fan relay. This switched signal will take the place of ( by-pass) the ECM (primary) and head switch (HD fan).

FireInMe17

Then that will be the next thing I try tomorrow morning, I'll keep you updated. Thanks for the help!

John in RI

iTrader: (167)

NO Problem,........

OrangeBird

iTrader: (1)

Just so you know , I may know generalizations about our car's wiring because electronics is a hobby for me and I know my way around a schematic fairly well . John knows the wiring of these cars wire for wire and is very well the guy to listen to when it comes to troubleshooting the wiring in our cars . kudos also to John for noticing this car has had an engine transplant , something I hadn't noticed when I first answered you , and the fact that such major work was done means the troubleshooting could prove far more challenging than on a vehicle with it's native organs . It sounds like your well on your way in the diagnosis and yea , I'll be checking in for your updates .

FireInMe17

Trying that jump doesn't seem to do anything...

John in RI

iTrader: (167)

If you had the key in RUN and touched a ground jump to the GREY wire and the GREY wire and each fan failed to operate,..... I'd suspect a bad fusible link first, ( you had said you had 12 volts - but not at what color wires had 12 volts ) bad relays second, bad wiring next, and bag grounds last.


( With Key in RUN ) Putting a jump ground-wire on Grey bypasses the temp switch and putting a jump ground-wire on Green/White bypasses the ECM


With the key OFF check the Orange wire for voltage @ each relay. If No/Low voltage check the fusible link

Check Ground @ each relay

With the key in RUN check Brown wire @ each relay for voltage

If all check OK,... replace with new Relays and re-test ( Be sure to check relay connectors for crud/dirty terminals first !! )

FireInMe17

I'll keep checking then. If all else fails my car doesn't have rear defrost, and I have a rear defrost switch, the fans might just end up getting ran into that manually. But I want to make every effort to get them to work automatically as it should, obviously don't want to have to worry about it! Haha thanks again John!