Electronics Need help wiring something up? Thinking of adding an electrical component to your car? Need help troubleshooting that wiring glitch?

91 LB9 Both Fans Died Need Help Diagnosing (Video Included)

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Old 01-19-2013, 05:14 PM
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Car: 1987 GTA Vert & 1991 GTA 5 Speed
Engine: 87 GTA-L98 91 GTA LB9
Transmission: GTA-700R4 & GTA T5
91 LB9 Both Fans Died Need Help Diagnosing (Video Included)

So just bought this car letting it sit in driveway idling to get warm to go get inspected. Son comes in and says wow your car is really hot you can cook on it. I paid him no attention. So I sit another minute or two and go outside and steam is going everywhere. Open the hood and long story short car is overheating.....

Get it cooled down and discovered the radiator is leaking right in the middle. But even worse both fans are not working.

Next day I check fans by wiring them to battery and they both come right on.

I go on to the relays and I find both on drivers firewall near brake booster. I ground the grn/wht wire from the ground on the battery and get nothing. As I understand this is suppose to turn fan on. Switch was in on position with engine off.

I try the same with the other relay and the corresponding (same pin location on other relay) wire I think it is the either the gray or brown wire. Still nothing. Switch was in on position with engine off.

I do not have the FSM yet to do troubleshooting. I do have a 1987 FSM but I am unsure if procedures are the same. Please help!

Not sure if this helps but here is a diagram

http://austinthirdgen.org/mkportal/m...ine_wiring.gif

By the way I checked all 20 amp fuses and none were blown. Not sure of location for radiator fan fuse.

Last edited by Slowridr; 01-20-2013 at 08:38 AM.
Old 01-19-2013, 08:50 PM
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Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
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Re: 91 LB9 Both Fans Died Help Diagnosing

Originally Posted by Slowridr
I ground the grn/wht wire from the ground on the battery and get nothing. As I understand this is suppose to turn fan on.
I try the same with the other relay
By the way I checked all 20 amp fuses and none were blown.
The 20A fan fuse you speak of is, as shown on the relay control circuit , not the fan circuit.

If you study the circuit diagram you will see both fans are fed from the batt through the relays by a common fusible link (D ) on the orange wire; probable link that is blown.
Put your DVM on the thick orange wire at the relay and see if you have 12V ;
if not the fusible link is suspect.
Grounding the control wire as you did with the key on , should make the relay(s) click, if they didn't then the relay them self are suspect

Not sure on your car but in some cars the fusible links are direct off the starter Pos terminal , in others off a common power block off the batt Pos
https://www.thirdgen.org/forums/elec...ble-links.html
https://www.thirdgen.org/forums/v6/6...ble-links.html
https://www.thirdgen.org/forums/elec...y-fusible.html
Old 01-20-2013, 08:22 AM
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Car: 1987 GTA Vert & 1991 GTA 5 Speed
Engine: 87 GTA-L98 91 GTA LB9
Transmission: GTA-700R4 & GTA T5
Re: 91 LB9 Both Fans Died Help Diagnosing

Ok so I shot this video. I hope this will help more than me trying to explain it does. I can not read those diagrams very well as you can see. Do you know of anywhere I can get a how to on reading those flow charts and/or using the voltmeter. I have one and if babied thru using it I can get the job done but I would like to be able to pick one up and do troubleshooting without bugging everyone else on how it should be done. In any case let me know what you think on whats in the video. I would really like to get these fans wired up correctly (not hot wiring to a switch) and get my car inspected. I can handle changing out the radiator on my own.


Last edited by Slowridr; 01-20-2013 at 08:27 AM.
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