89fast5oh

1991 Trans Am wiring harness in 1985 Camaro.

I haven't had a problem cooling the car all year and tonight when I was out I noticed the temperature gauge climbing up. I stopped and had a look under the hood and noticed both fans were off.

They won't come on with the AC turned on, the AC pressure switched leads jumped, the aux fan relay grounded out, or the passenger cylinder head switch closing while the car is running or shut off.

I tested and swapped out the relays with no change. There is power to the Orange wires of the relays. The 20 amp fuse in the main panel is not blown.

It got dark so I didn't have anymore time to look at things. But when I did have the relay for the aux fan jumped I measured the voltage across the fan connector and got about 6 volts. Battery is showing 12.5 key on, engine off.

If there is full battery voltage to the Orange wires at the relays I guess there has to be a broken/burnt wire somewhere. But what circuit would control the operation of both fans?

BHicks

Have you checked that the fan motors are still good?

89fast5oh

Not yet, but wouldn't it be strange that both motors quit in a span of 1 hour?

NufNuffZ28

iTrader: (10)

One could of already been INOP and the other just went out.

I start with hot-wiring the fans and working backwards. That way you can rule the fan motor out to start with.


Also, when you do hot-wire the fan, check the speed. If a motor is going out it will work, but slowly(had that happen just last week). Also, when you do this check the wire you use to check it with. If it gets hot quickly the motor is most likely bad and causing the wire to heat...

BHicks

Yea it would be a sight to see both stop within an hour.
Reason I asked, was on my car, which is bone stock. The driver side fan comes on first. The passenger side fan won't come on unless it gets like 240 or so.
Just wondered is the secondary May have been already shot and the primary just one bit the dust.
That secondary fan should run if it's good just by turning the key on, and disconnect the lead off the sensor at the passenger side head, and ground that lead out with a paper clip or something to the chassis or something in reach.

89fast5oh

My passenger fan is wired to the ECM and operates automatically just like the drivers fan. Both fans were visually running and cooling the engine one hour before.

When I get a chance I will power the motors directly. I didnt have a chance to test the drivers fan connector for power yet.

Joe Tag

iTrader: (4)

If you have 12v at the relay on orange wire and 6v at the fan I would look close at the connectors to see if they are cooked and just getting poor contact. If you are getting 6v at the relay orange wire, do you have a fusible link on it at the battery? It may be partially broken.

BHicks

Yes they are both controlled by ECM. The sensor under the t stat housing in the intake controls the primary, one in passenger head controls secondary. Unless one locked up and burnt a fuseable link or something?
Do a search here for wiring diagram, I've seen em, hopefully that will point you in right direction. I hate electrical issues

Joe Tag

iTrader: (4)

The aux. fan is controlled independently from the ECM by the temp switch in the passenger side head. Only time other than the switch turning it on that it comes on is with the A/C. Here's a diagram for it, but I think you will need to look at the connectors and the fusible link. Bottom right is the fan circuit. If you have the complete harness from the 91, the fusible link should be tied to the heavy charging wire from the alternator.

89fast5oh

I will have a look at the fusible links and relay connectors today. My secondary fan is wired to F8 on the ECM connector. The temperature set points have been altered in the programming so the fan comes on just after the primary fan.

Joe Tag

iTrader: (4)

Sorry, you did say that earlier and I missed it. I was thinking stock setup.

89fast5oh

Both fans work great when hardwired to the battery. When I jump the relays I get battery voltage at the fan power wire connectors. When I have it all hooked up and ground the relays or temp sensor in the passenger cylinder head there is nothing.

That has to be impossible. Fans work, power to the connectors but nothing will work....

Joe Tag

iTrader: (4)

Did you pull the plugs at the relay and check them? Try jumping the orange to black and red wire on the relay connectors and see if the fan runs. You can get 12v and still not have enough current flow to operate the fan. If both fans quit at the same time I'd be looking at the connection to the battery or the joint where it splits off to the two relays.

89fast5oh

When I pull the relay and with key on and jump the orange and black/red wire nothing happens. But the fan connector shows 12v. Jump the fan to battery and it works. Both fans and relays test the same.

Joe Tag

iTrader: (4)

Did you test the fans through the connectors or without any? Run a temporary hot wire from the battery to the black and red at the relay connector. If that works run a wire from the orange at relay to the fan. Eliminate wires in your testing from your circuit to see which is faulty. Still leaning towards a bad supply from the battery since both quit at once.

Joe Tag

iTrader: (4)

Check your grounds for the fans if you didnt use the harness plugs to test them. Usually they are both attached to the core support by one screw.

89fast5oh

Hot to black/red at the relay worked.

I checked the fusible link at the battery and it seemed still solid. But after moving it around a bunch the fan came on.

So that was the problem. Ill keep an eye on it and replace the fusible link at the first sign of trouble again.

Do you know what size fusible link? The diagram says .5 is that the size of fusible link to use?

Joe Tag

iTrader: (4)

Glad you found it. .5 is the rating in sq mm. Don't keep an eye on it, fix it. Any parts store should have them.

89fast5oh

The positive wiring right off my battery seems pretty sketchy. It the fusible link supposed to go between the positive terminal and the heavy duty 2 wire weather-pack connector? It looks like a wire comes off the positive connector, then a fusible link is soldered to that and it goes into the 2 wire connector.

Joe Tag

iTrader: (4)

The fusible link has a more rubbery type of insulation on it usually as opposed to the harder plastic type on harness wire. It will have a rating marked on it, go by that, not what's in the diagram. Still a good idea to check your fan grounds. A bad connection will add resistance and could cause the link to blow again. I like to have heavy load grounds have their own attachment points rather than having a few on the same screw.

89fast5oh

Well 2 years later it did it again. I never replaced any wires the first time around because it started working and didn't do it again.

This time I took apart the large 2 wire C145 connector off the positive side of the battery and it was melted on the fan power lead wire.

Is the C145 connector with the .5 Rust fusible link D available to buy?

https://www.thirdgen.org/forums/atta...kschematic.pdf