Dual Fans not turning on
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Joined: Aug 2006
Posts: 44
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From: Canada
Car: 1983 Camaro Z28
Engine: 355 Tuned Port with Vortec Heads
Transmission: T56 six speed
Axle/Gears: 373 10-bolt
Dual Fans not turning on
Hi, I was wondering if somebody can offer me some advice. I have an issue with my Dual fans. They are not coming on when I jumper the ALDL. I understand that only the primary fan should come on when in diagnostic test mode.
As of right now I'm trying to get my car running after roughly 14 years of it sitting in my garage rebuilding it. The motor is a 355 Tuned Port with Vortec heads. I've had many parts cars over the years so this kind of a 'FrankenCar".
It's an 83 Z28 with a rebuilt 1988 5.7 350 TPI and I have 92 dash installed because I liked the instrument cluster at the time. I've spent a lot of time over the years re-pinning, soldering wires, etc. to get everything to function as it should. I've been very meticulous in my ways to get it right. I've always hated when previous owners of cars butcher wiring harnesses and don't solder any connections.
So, Last week I decided that I was going to fire it up for the first time. Without getting too involved in the start up...I ended up only running it for a minute because of some minor "my fault" issue's. During this process I fried my starter. No biggie...one is on order.
Now that I'm waiting for a starter to arrive I decided to look at the cooling system fans and check to see that they are going to function normally by the ecm and that the secondary fan turns on with the switch on the passenger head. I guess when I started my motor I figured they would work with no problems. Even though I ran my motor for only a minute it didn't get hot enough to turn the fan on. I previously tested the fans directly to the battery before starting the motor and they work!
Right now I noticed that after a lot of checks and double checking my fans won't turn on. I can check the relay connectors for both fan relays for the proper voltages and this is what I got.
Primary fan relay
Orange wire - 12v+
Tan/Wht - 12v+
Grn/Wht -ground wire controlled by ECM...This works, I've tested it.
Blk/Red -going to the fan...this wire is good, also tested it.
Secondary fan relay gives me the exact same result with the exception that I know the ground is controlled by the switch on the passenger head.
Fuse's and fuseable links I assume are good or I wouldn't be getting the 12v+ on the orange and tan/wht wires.
This is what I've noticed...I am getting 12v+ on the tan/wht wires at the relays which should trigger the relay to supply the 12v+ from the orange wires to the blk/red wires going to the fans. I will mention that I've tried to ground the secondary fan by disconnecting the switch at the passenger head and grounding the wire, that fan does not come on.
I hooked up a 12v test light to the tan/wht wires and battery ground, it did not light up, then i checked the voltage on those wires and still got 12v+. Same goes for the secondary fan relay connector.
It's like the voltage disappears when hooked up to a load (remember ALDL is in test mode). With the relays connected i probe the tan/wht wires...No voltage. When I disconnect the relays and check...I am getting 12v+ like I should.
I even switched out the alternator just to see if there was a difference...Nope! I was thinking the alternator was causing a drain on the system.
Anyway, I hope I included enough information. Any help would be appreciated. Thanks!
As of right now I'm trying to get my car running after roughly 14 years of it sitting in my garage rebuilding it. The motor is a 355 Tuned Port with Vortec heads. I've had many parts cars over the years so this kind of a 'FrankenCar".
It's an 83 Z28 with a rebuilt 1988 5.7 350 TPI and I have 92 dash installed because I liked the instrument cluster at the time. I've spent a lot of time over the years re-pinning, soldering wires, etc. to get everything to function as it should. I've been very meticulous in my ways to get it right. I've always hated when previous owners of cars butcher wiring harnesses and don't solder any connections.
So, Last week I decided that I was going to fire it up for the first time. Without getting too involved in the start up...I ended up only running it for a minute because of some minor "my fault" issue's. During this process I fried my starter. No biggie...one is on order.
Now that I'm waiting for a starter to arrive I decided to look at the cooling system fans and check to see that they are going to function normally by the ecm and that the secondary fan turns on with the switch on the passenger head. I guess when I started my motor I figured they would work with no problems. Even though I ran my motor for only a minute it didn't get hot enough to turn the fan on. I previously tested the fans directly to the battery before starting the motor and they work!
Right now I noticed that after a lot of checks and double checking my fans won't turn on. I can check the relay connectors for both fan relays for the proper voltages and this is what I got.
Primary fan relay
Orange wire - 12v+
Tan/Wht - 12v+
Grn/Wht -ground wire controlled by ECM...This works, I've tested it.
Blk/Red -going to the fan...this wire is good, also tested it.
Secondary fan relay gives me the exact same result with the exception that I know the ground is controlled by the switch on the passenger head.
Fuse's and fuseable links I assume are good or I wouldn't be getting the 12v+ on the orange and tan/wht wires.
This is what I've noticed...I am getting 12v+ on the tan/wht wires at the relays which should trigger the relay to supply the 12v+ from the orange wires to the blk/red wires going to the fans. I will mention that I've tried to ground the secondary fan by disconnecting the switch at the passenger head and grounding the wire, that fan does not come on.
I hooked up a 12v test light to the tan/wht wires and battery ground, it did not light up, then i checked the voltage on those wires and still got 12v+. Same goes for the secondary fan relay connector.
It's like the voltage disappears when hooked up to a load (remember ALDL is in test mode). With the relays connected i probe the tan/wht wires...No voltage. When I disconnect the relays and check...I am getting 12v+ like I should.
I even switched out the alternator just to see if there was a difference...Nope! I was thinking the alternator was causing a drain on the system.
Anyway, I hope I included enough information. Any help would be appreciated. Thanks!
Last edited by 355sbcTPI; Mar 25, 2015 at 09:58 PM. Reason: Grammer
Joined: Dec 2005
Posts: 4,795
Likes: 15
From: St. Cloud, MN
Car: 1984 Trans Am
Engine: LS1383 in work
Transmission: Magnum F - to be installed
Axle/Gears: Zexel Torsen 3.73, 28-spline mosers
Re: Dual Fans not turning on
If the fans work by supplying power directly to them, then we know their good. Grounding the switch wire to chassis ground should fire over the secondary fan.
Just a question, but with no starter, how are you running power through the circuit? Shorting the wires directly together?
does your fans turn on when you turn the AC on? They should. If they do, then you know the circuit is good.
If the fans don't come on, check the main fan relay, the circuit still goes through there.
There is also a fuseable link just in front of the fan relay that if it burned up, you're fans won't work. I'm only considering this because you said you fried your starter and it's possible it had more detrimental effect than you initially thought.
Just a question, but with no starter, how are you running power through the circuit? Shorting the wires directly together?
does your fans turn on when you turn the AC on? They should. If they do, then you know the circuit is good.
If the fans don't come on, check the main fan relay, the circuit still goes through there.
There is also a fuseable link just in front of the fan relay that if it burned up, you're fans won't work. I'm only considering this because you said you fried your starter and it's possible it had more detrimental effect than you initially thought.
Thread Starter
Junior Member
Joined: Aug 2006
Posts: 44
Likes: 0
From: Canada
Car: 1983 Camaro Z28
Engine: 355 Tuned Port with Vortec Heads
Transmission: T56 six speed
Axle/Gears: 373 10-bolt
Re: Dual Fans not turning on
Hi Ozz,
Just the other day I was still trying to diagnose what the problem was and I noticed that I did not have the tan/wht wire hooked up to the fuse panel. This wire runs through the C207 connector (then changes to a brown wire) by the ecm and hooks up to the 20amp fan fuse. I believe that I did not hook it up at the time because I wasn't sure how I was going to wire it up to the fuse panel. So, I left it as is and forgot about it. I didn't remember because the fan fuse was good and it was getting power when I checked it with my meter.
As for the disappearing voltage...I can only tell you that when I started to check the alternator connector with the three wires, I could excluded that an alternator drain was happening. I was also getting the disappearing voltage at that connector as well. With the alternator connector unplugged, again I checked both relay connectors (without relays connected this time) and only one had the disappearing voltage and the other had no voltage at all, but this time it was the grn/wht wire on the secondary fan circuit. While I was doing this testing I hadn't hooked up the fan wire to the fuse panel yet.
As of right now, connecting the fan wire has solved my issue of the fans not working. The primary fan turns on with the ALDL jumpered and the secondary fan turns on when I jumper the A/C high pressure switch. All is good!
Just to answer your questions...my starter is still in place it just won't do anything, no clicking from the solenoid. Also, I don't have my A/C hooked up because of the motor change years ago...the freon was discharged. I did turn on the A/C to see if the fans would come on and they didn't. But that is with the motor not running and ignition on.
Thanks for a quick response Ozz, I will try and re-create my issue at later time to see if I can pinpoint what the issue was. My main concern was automatic control of the primary fan for breaking in the motor.
Just the other day I was still trying to diagnose what the problem was and I noticed that I did not have the tan/wht wire hooked up to the fuse panel. This wire runs through the C207 connector (then changes to a brown wire) by the ecm and hooks up to the 20amp fan fuse. I believe that I did not hook it up at the time because I wasn't sure how I was going to wire it up to the fuse panel. So, I left it as is and forgot about it. I didn't remember because the fan fuse was good and it was getting power when I checked it with my meter.
As for the disappearing voltage...I can only tell you that when I started to check the alternator connector with the three wires, I could excluded that an alternator drain was happening. I was also getting the disappearing voltage at that connector as well. With the alternator connector unplugged, again I checked both relay connectors (without relays connected this time) and only one had the disappearing voltage and the other had no voltage at all, but this time it was the grn/wht wire on the secondary fan circuit. While I was doing this testing I hadn't hooked up the fan wire to the fuse panel yet.
As of right now, connecting the fan wire has solved my issue of the fans not working. The primary fan turns on with the ALDL jumpered and the secondary fan turns on when I jumper the A/C high pressure switch. All is good!
Just to answer your questions...my starter is still in place it just won't do anything, no clicking from the solenoid. Also, I don't have my A/C hooked up because of the motor change years ago...the freon was discharged. I did turn on the A/C to see if the fans would come on and they didn't. But that is with the motor not running and ignition on.
Thanks for a quick response Ozz, I will try and re-create my issue at later time to see if I can pinpoint what the issue was. My main concern was automatic control of the primary fan for breaking in the motor.
Last edited by 355sbcTPI; Mar 27, 2015 at 04:53 PM. Reason: additional details
Thread Starter
Junior Member
Joined: Aug 2006
Posts: 44
Likes: 0
From: Canada
Car: 1983 Camaro Z28
Engine: 355 Tuned Port with Vortec Heads
Transmission: T56 six speed
Axle/Gears: 373 10-bolt
Re: Dual Fans not turning on
Thanks deadbird,
Diagrams are always a bonus!
Diagrams are always a bonus!
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