I know one is the fuel pump relay, but what are the other two? I built a custom engine and im not using the computer at all. Do I guess i can follow the wires and see what they go to . Im jus trying to eliminate as much clutter as possible. Thanks guys!

 

Year,make, and model would help...

Fuel Pump
Mass Air Flow Power Relay
Mass Air Flow Burn-Off Relay

 

if its at MAF TPI set up then I would guess the other two are MAF, one is MAF power the other is MAF burnoff

 

Ok, what if its the TBI version? 92 TBI

 

 

Where are the other 2 relays? I see the fan relay but that's different.

 

Are those of us that are not rocket scientists supposed to be able to read that Bob???

 

Fuel pump will have five wires
16ga gry
16ga orn
18ga dk grn/wht
18ga blk/wht

Coolant fan
12ga blk/red
12ga red
18ga dk grn/wht
18ga brn

AC
18ga dk grn
18ga dk grn/wht
18ga lt grn/blk
18ga pnk/blk

MAF/burnoff relays are limited to older TPI/V6 cars. Your TBI car is speed density. 90-92 dual fan equipped cars will have a second fan relay. Some 90-92 cars moved the AC relay from the firewall to the HVAC box, so really, you need to figure out the wire color/sizes to identify the relay in question

 

Its just a bunch of resistors, wires, stepper motors, relays and sensors and stuff... Come on. not too hard.

 

Hi Pocket ,

On the 89 V6 that I own, the 3 relays on the firewall are Fuel pump , Radiator fan , and A/C clutch . The MAF has a power relay near the radiator and there is no burnoff relay (3 wire MAF instead of 5) . You are right that every different engine/induction system seems to have a different placement of the relays and there is no "one size fits all" description of the location of the various relays . Using the colors of the wires as you suggest is the only sure way of knowing exactly which is which .

 

Pocket.. As always, much appreciated buddy. Your awesome.

 

Pocket,
So I found out that I have an Auxiliary Fan Relay next to the original fan relay and the fuel pump. My question is the big orange wires coming out of those they run to a 20 amp fuse and a big connector. Can i just run the oranges wires from that connector to 12v Batt Power?

 

Those wires are fused hot, they get there power from the battery directly via connectors and a fuse

 

Alright cool I'll try that and see if i burn the damn thing down lol. Kind of making my own wiring harness from the original

 

Dual fan cars changed the 12ga color from red to orange and for 90-92 TPI cars the wire went to the battery cable inline connector. Theres a short length of fusible link on the cable side making repairs difficult

 

If I remember correctly, one orange wire has a fuse link 20AMP (fans) and the other one has an in-line 20AMP fuse (fuel pump). That was the set up for most of year/model. The ECM was controlling the fuel pump and fan#1 so without it, it won't work. You'll need to have the fan relay triggered by a temp switch on the engine and the fuel pump activated by ignition or other means. The fan#2 is temp switch activated on right side of engine head.


Best of luck

 

Good information

 

Pocket you sure seem to know your electrical, Im inpressed!!
I have an 89 Iroc that has some serious wirin hacked.
I have a pontiac harness and checked all the ECM pinouts against the Iroc and they seem to be the same.
I am getting voltage off C1 on the ECM instead of ground to the main fan.
I jumped the relay and the fan runs fine ' but for the life of me even using a power probe I just cant seem to figure this one out.
I cuold cheat ang run a ground from the sensor on the intake like this guy did" but I'm hoping to use the ECM to control the AC system and the cooling fans.
I"m thinking feedback' but I'm pretty sure all the Ecm grounds are grounded.
I grew up in the 70'2 and have been building my own cars all my life but this one has me fooled.
I have a friend that buys these cars and brings them to me to get everything working' and then to the interior shop and the painter so the new owner can keep the dream alive.
Any help would be appreciated.
Thanks Bob W

 

If you want @Pocket to reply you can include his name with a @ and select from the list. That should send him a notification.
Cheers

 

Or just send a PM

 

@Pocket We'd love to have your wiring expertise in our V6 FB group if you're on FB! Have a member that's been chasing wiring issues for a while.

FB links apparently don't post here on the group, but if you search FB for "V6 Thirdgen Camaros & Firebirds" or "519767201760619" it'll come up.

 

Oof, ECMs get tricky to troubleshoot

I'd start by looking at factory diagrams and making sure the power/grd circuits are correct. Since most of the outputs are 12v or grd, then you can test each function. If you're getting 12v instead of grd, then you may have a bad ECM. They're all +30 y/o at this point and not exactly the most robust units

It may be time to consider an aftermarket ECM and wiring overhaul. A used unit may get the owner by for a while

Diagrams:
https://charm.li/Chevrolet/
https://austinthirdgen.org/thirdgen-wiring-diagrams/