What are the 3 RELAYS on the Firewall??
#1
What are the 3 RELAYS on the Firewall??
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!
#2
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Re: What are the 3 RELAYS on the Firewall??
Year,make, and model would help...
Fuel Pump
Mass Air Flow Power Relay
Mass Air Flow Burn-Off Relay
Fuel Pump
Mass Air Flow Power Relay
Mass Air Flow Burn-Off Relay
#3
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Re: What are the 3 RELAYS on the Firewall??
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
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#8
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Car: 92 Firebird
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Re: What are the 3 RELAYS on the Firewall??
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
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
#10
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Re: What are the 3 RELAYS on the Firewall??
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
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
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 .
#11
Re: What are the 3 RELAYS on the Firewall??
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
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
#12
Re: What are the 3 RELAYS on the Firewall??
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?
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?
#13
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Re: What are the 3 RELAYS on the Firewall??
Those wires are fused hot, they get there power from the battery directly via connectors and a fuse
#14
Re: What are the 3 RELAYS on the Firewall??
#15
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Re: What are the 3 RELAYS on the Firewall??
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?
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?
#16
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Car: '91 Firebird Formula
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Transmission: Tremec T56
Axle/Gears: Moser 9" Eaton Truetrac Motive 3.89
Re: What are the 3 RELAYS on the Firewall??
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?
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?
Best of luck
Last edited by SbFormula; 02-26-2024 at 04:07 PM.
#18
Re: What are the 3 RELAYS on the Firewall??
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
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
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Car: '91 Firebird Formula
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Transmission: Tremec T56
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Re: What are the 3 RELAYS on the Firewall??
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
Cheers
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Car: 1989-92 FORMULA350 305 92 Hawkclone
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Re: What are the 3 RELAYS on the Firewall??
Or just send a PM
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