Hi all, first post here, yippee!

I've always referenced the posts on this forum while working on my own Bird but it seems I've finally gotten to the point that I have to make my own post. Now, bear with me, as my only experience with cars before this one was my Celica which is... well, wildly different. 1985 Pontiac Firebird Trans Am.

So, I've done all the usual tests; the fan doesn't turn on when the AC is on, but I am getting power to the relay and the fuses. The wiring for the fan motor is not getting power and presumably, neither is the fan, but I can't very well get my hands down there to check with the multimeter.

I would like to try and jog or jump the fan motor before I go crazy replacing it, but I'm not entirely sure exactly how to do that. I know there's a couple different ways and I'm looking for whichever method will be easier, as the only time I get to work on this car is before work in the morning.

I've already done so much to this poor girl and she just keeps throwing issues at me. But when she runs, oh, she flies. She wants to go, I just need to get her there- so any advice is welcomed.

Thanks in advance, and I'm happy to be here!

 

Is the ac system charged?

What type of motor is in it / what induction system? aka TPI or carb?




its easier to reach the fan connector from the bottom really lol but its very simple and just pops off




You should have positive power to the fan but the fan turns on when the ground is grounded which is by the fan switch or the ECM if you have TPI.

 

The AC runs cold so I'm assuming it's charged.

I have the 305 TPI.

Thank you for the advice though! I'll check that out before work tomorrow

 

The Big Red Wire at the fan relay is the 12V source to it. if that has power, then ... that part is OK.

If you can't check this at the fan itself, how do you know it? Are you saying that the Big Black/Red Wire at the fan relay doesn't get 12V? If so, then that's the fault of the relay. Either it's bad, or it's not getting the command to turn on.

The relay has 4 wires. The above 2, and 2 smaller ones: a brown, and a green w white stripe. The brown gets 12V when the key is turned on, and things that command the fan, ground the grn/wht wire. Those would be, the fan switch in the head, maybe a pressure switch on the high side of the AC, and maybe something from the ECM. I don't think the ECM is involved in your car butt I don't know for sure, butt it doesn't matter all that much just yet anyway.

When the key is on, check for 12V on the brown wire. If there's power there, then ground the grn/wht by sticking a wire up into the connector from behind and shorting it to ground. The relay should click. When the relay clicks there should be 12V on the blk/red wire and the fan should run. If there's no 12V on the blk/red, then check to be sure there's still 12V on the red, as a bad (such as, corroded) connection in that circuit will provide enough 12V to work a multimeter since it only draws a few microamps, butt may have trouble delivering 30A or whatever, to run the motor. If there's no 12V on the blk/red with the relay operated butt there still is on the red, then the relay itself or its connector, is bad.

If OTOH the whole thing works when you jam the grn/wht wire, then the problem is with whatever is supposed to command the relay, in your car.

 

Another thing could be is the wires get corroded right at the relay connector... relay on this I think should be on the side of the radiator / core support. the wire covering gets eaten aways by the I think grease or whatever they put in the connectors... turned out mine was touching and grounded out so power wasn't sent to the fan. I put some liquid electrical tape on the wires and it works good now. Something to look at.

 

I can't get my hands to the motor itself (gonna be removing things so I can tomorrow) but the wires all leading to the fan motor are getting no voltage.

As for the wires, this car sat for 13 years and its gotten quite hard to distinguish color, but I've been picking away and wiping them all down to see what (faded) color they are, so the rest of your reply will come in handy- thank you!!

 

Oh! Simple way to test the fan is the pressure switch in the hard line that goes from the condenser to the evaporator.. the fan pressure switch is there.. it shoud be along the frame rail.

Disconnect the electrical connector and the fan should come on.

 

This is actually really good to know. Mine is absolutely slathered in the grease, so I'll take a look at that as well.

 

Hawk's makes a replacement connector which I believe is also the same as the fuel pump connector.... which also gets all fugly....

... ive been meaning to replace mine but mine appears to have 1 more wire than the connector / the 4 sofa mentioned....so ive been meaning to investigate ...aka....the liquid tape worked so I forgot about it. / said screw it lol

 

Cooling Fan Electric Connector:
This is a Quote from an amazing Thread by QwkTrip: LS Swap Electrical Connectors

 

That's not accurate; the Electric fan set-ups in all Thirdgens have GROUND at all times and power is sent to the fan thru the relay only after the relay gets a signal to turn the fans on. These fan systems are real basic, but still very specific depending on the year and induction type.

This schematic is from the 85 Camaro Shop manual; The primary 'driver' for the fans is the ECM itself; "Switched" ground signal to activate the Relay comes only from the ECM. (The AC pressure switch feeds switched ground signal to the ECM,...... then ECM-to-Relay.) There is no head-mounted sensor on your car.

** 86 TPI *should* be the same but changes were made in 87 when dual fans were introduced. )




You can start your investigation at the fan, ( Hot wire / "jump" the fan itself with power / ground to be sure the fan motor works ) or; start @ the power/ground side of the equation. (Ground @fan ? Power at all times from ORANGE wire @ Fusible Link ? Power from FUSE-to-Relay when key is in RUN ? ) The just work your way thru the system a step at a time and you will find the problem.

Fusible Link "D" is the Fusible Link on the Battery Cable and G117 Ground is screwed to the pass side upper radiator bracket; Good Luck !

 

As already stated Different Model-Years and Different Engines go about activating the Electric Cooling Fan/ Fans with Relays in Different ways.
The Relays use either a Thermostatic-Switch, or the PCM with a Coolant Temperature Sensor.

However the following is always the same:
-The Electric Fan/ Fans always have a Constant Negative/ Ground Connection and are Activated by Positive Connection from the Corresponding Relay.
-The Electric Fan Relay/ Relays always have a Constant Positive Connection and are Activated by Negative Connection.

 

my bad thats what i meant. power to the relay

 

sometimes these old wires can be tricky. might need to trace them carefully.