Yet Another Engine Fan Post

[CharlieB]

Hi all,
For the past several days I have been trying to figure why the radiator fan on my '76 Spider is not coming on. I know the subject has been discussed on several posts on the forum, but i can't seem to find the solution.
I have ruled out the thermostat and there is no air in the system.
If I connected power directly to the fan it spins. So the fan itself is good.
I unplugged the 2 wires going to the thermoswitch on the bottom of the radiator, connected the 2 wires together and turned the ignition to 'on'. The fan does not come on.
If I'm not mistaken, the fan should come on...correct?
I have cleaned up every wire connection I can find, but no luck.
Is it possible the thermoswitch is bad?
Are there other tests I should perform?
I'm not sure if this is related, but my horn does not work either.
Any help is greatly appreciated.
Thanks,
Charlie

[Nut124]

Charlie,

Measure voltage vs ground at the connector that connects to the radiator thermal switch, on the harness side. One of them should register a voltage.

If no voltage found at the switch connector, check the connector going to the fan; One of the wires (Lt Blue) should have 12VDC. If you find 12VDC here, but not at the switch connector, then, disconnect the thermal switch connector and short the fan connector. This should send 12VDC to the switch.

If you do not see 12VDC now at the switch connector, then the wiring is bad between the fan harness and the switch harness. If, now, you do see 12VDC at the switch harness, then the fan motor is likely bad.

You really need a wiring diagram. And then follow 12VDC from point to point, one step at a time.

Typically, away from the instr cluster, any switching in the field (engine bay), switches the ground side. In the dash, many switches switch the 12VDC supply side.

[TX82FIAT]

Tip, fan switch circuit should be hot 100% of the time. Ignition on should not mater.

[CharlieB]

Thanks guys,
I'll check voltage today. Nut124, when you say 'disconnect the thermal switch connector and short the fan connector' do you mean connect the two wires going to the switch on the radiator? I have done that, I just want to make sure I'm doing it correctly.
I do have wiring diagrams, I guess I just need to be more methodical in my approach. I tend to jump around too much.
I'll report back after testing for voltage.
Thanks again,
Charlie

[Nut124]

Charlie, If the fan does not run when the switch connector is shorted, then either:
- The fan is bad
- There is no 12VDC coming to the fan
- The wire is bad between the fan and the switch

I suggested shorting the wires at the fan connector. This would cause an arc if the switch was connected and was closed, so not really a good idea. That is why I said disconnect the switch to avoid potential short circuit.

Do you have a multimeter? If there is 12VDC at the fan, check the resistance of the fan motor. It should measure in the low single digits, 2-3 ohms. If infinite or high, then the motor is bad. If this checks out, then a wiring problem between fan and the switch, or between switch and ground.

[spider2081]

I believe the coolant fan circuit changed over the production years of the Fiat Spider.
Both the fan and the horn are protected by fuse 1 (closest to the steering column)

I'm pretty sure the 76 Spider has a coolant fan relay. Located under the hood on the driver side fender well. It should be the middle relay in the row closest to the engine.

This relay when energized supplies voltage to the fan. Voltage will not be present at the fan until this relay is activated. The thermostatic switch at the bottom of the radiator grounds one side of the relay coil and that activates the relay. Power is supplied to the other side of the relay coil from the top of fuse 10. (unprotected) The relay contact is powered from fuse 1 which has power when the ignition switch is in the "run or Start" positions.

Questions: Have you checked both fuse 1 and fuse 10
when the wires to the thermostatic switch are connected together, do you hear a relay click?

[CharlieB]

All fuses are good and the relay is new. I have voltage at the relay but nothing at the fan harness. I'll replace the wires tomorrow, if I can find them. My wiring is a mess and I can't tell what color most of them are.
Thanks,
Charlie

[spider2081]

I have voltage at the relay but nothing at the fan harness.

Didn't your first post state neither the horn or the radiator coolant fan work? They both are powered from fuse 1
Have you tested for voltage at the top and the bottom of fuse 1? A visual of a fuse does not check if the fuse is making electrical contact.

I'm not positive the wire diagram I have is 100% accurate with regards to the ignition switch positions.
At the relay socket you should have voltage in 2 of the relay socket terminals terminal 30 gets voltage from fuse 1
Relay terminal 85 gets voltage from fuse 10
Relay terminal 87 sends voltage to the fan when the relay is energized by the thermostatic switch at the bottom of the radiator.
You did not mention if you hear a relay click when the thermostatic switch wires a connected together and the ignition switch is in the "start or run" positions

[CharlieB]

EDIT:
I do have voltage at fuse 1. I checked it at the top and bottom wires at the panel.
I do have voltage at pins 30 and 85 AND 86 of the fan relay.
I do hear a click at the relay when I touch the 2 thermoswitch wires together with the ignition on.
On a hopefully unrelated note, I found this at the first upper connection to the panel there is a wire that is completely disintegrated.

Is this relevant to the issue?

[18Fiatsandcounting]

Charlie, I don't know about the disintegrated wire on the left in the picture, but I wanted to make sure I understand what you're seeing. In a '76 spider the cooling fan (and horn) go through Fuse 1 (Fuse A), which is the one closest to the steering column when the fuse box is installed. Fuse 1 has a black wire to one side (coming from the alternator/battery) and a viola (purple) wire that goes to the fan relay.

Note that in your model year, the cooling fan can come on without the ignition being on, so you shouldn't need to turn on the ignition to test things.

So, with ignition off, you should measure +12V between terminal 30 on the fan relay (purple wire) and body ground.

Here's the tricky part. The power for the fan relay (not the fan) goes through Fuse 10, the one furthest from the steering column. So make sure Fuse 10 is OK: power comes in from an orange wire that goes to the voltage regulator, and power goes to the fan relay through a light blue/black wire to terminal 85 on the fan relay.

The fan switch at the bottom of the radiator just grounds the fan relay. Switch comes on, relay is now grounded and clicks on, +12V for the fan goes through Fuse 1, then relay, then to the fan through a light blue wire. The ground side of the fan (black wire) is always grounded.

Hope this helps.
-Bryan

[CharlieB]

Hi Bryan,
Thanks for the info. I'll take a closer look at fuse 10 and report back.
I was getting voltage readings with out the ignition on but I didn't write those down. I'll go do that in the next hour or so.
There has to be a lose wire or dirty connection somewhere. Something simple...I hope.
Thanks again,
Charlie

[18Fiatsandcounting]

If your horn works, then Fuse 1 is OK, and I would turn my attention to the wiring (and voltages) around the relay. Make sure it's really the radiator fan relay (and not some other relay). The fan relay should have purple, light blue/black, black, and light blue wires going to it. Purple is +12V from Fuse 1, light blue is the power for the fan, and the light blue/black and black wires turn on the relay. Black is the ground, and light blue/black is the +12V for the relay (from Fuse 10).

-Bryan

[CharlieB]

Well my horn still does not work. So should I start there?
I did measure voltage at fuse 10 and got 11 volts. At pin 30 of the fan relay I only have 7 volts and nothing on any of the other pins. Both of those readings are with the ignition off.
With the ignition ON I get 6 or 7 volts at pin 30, and 11 volts at both pins 85 and 86. Zero volts at the fan harness.
Everytime I measure I get more confused.
Thanks,
CB

[18Fiatsandcounting]

Well, I know it doesn't seem like it, but I think this is progress!

Since your horn and fan both don't work, and they are on the same unswitched circuit (Fuse 1), my guess is that something is wrong with Fuse 1 or the wiring to it. The black wire of fuse 1 should connect directly to the output terminal of the alternator (which is itself always connected to the battery), so that black wire should have +12V on it at all times. The other side of the fuse is the purple wire which goes to the relays for the horn and the cooling fan, so it should also have +12V on it as well. Or whatever your battery voltage happens to be. 12.6 is a fully charged battery.

Start with measuring the voltages on both sides of Fuse 1 (black wire and purple wire) and we'll go from there. If they aren't at 12 volts at all times, something is wrong.

By the way, I believe Fuse 1 is a 25 amp fuse, which is a bit unusual for a Fiat. Not that it makes a difference as long as it hasn't blown.

-Bryan

[CharlieB]

Thanks Bryan, I looked at the deteriorated wire a little more and found that it goes from the fuse box, to an inline fuse under the dash near the fuse box then through the fire wall. I found it under the hood where it connects to a 2 terminal connector the female end of the connector has 1 wire that is looped back to the connector (jumper wire, i think is the term). The deteriorated wire connects to the one of the male terminals on the connector and has another length of wire attached to it at the connector. This other length of wire just stops. It's not attached to anything and it is a bare wire, or what's left of a wire. There is nothing at all on the end. The other male terminal has a gray wire with a red stripe. This wire also has a length of wire attached to it that just stops with nothing on the end. So basically the deteriorated wire and this other wire are connected together with ends going to nothing. The deteriorated wire is/was pink. The scary part is I measured 12 volts on the deteriorated wire. I peeled back some of the casing around the big bundle of wires going through the firewall so I could get a better look. When this wire had it's 'meltdown' it damaged some of the wires that were touching it.
I'll send a picture when I get to my computer if that helps. This is fuse #9 and I think the inline fuse is 28/4. Connector C4. I know this fuel pump and ignition mode related but the fuel pump works fine. My only issues are the horn and fan. Weird.
So, for the moment I need to fix this issue. Then I'll address the horn and fan problem. I'll take your advice as usual.
Thanks
CB