Cooling fan and relay issue

[Wizbangdoodle]

Ok, I've got an issue that is making me scratch my head.

I had suspected my cooling fan circuit was not working several months ago before I sent my car off to paint. I had it idling and it got up to about 215* before I shut it off, the fan having never kicked on. Fast forward to now and I have confirmed there is a problem somewhere. I have a sensor just before the water neck on my engine (408W) with the green wire labeled "Fan Thermo Switch". My understanding is that after this sensor heats up, it reduces resistance and runs that green wire to ground, which triggers the coil on the fan relay and sends 12vdc to the fan. Well, I figured I just used too much teflon tape on the sensor, so I tried grounding the green wire to the engine to get the fan to turn on. Nothing.

I then went to the green wire, Also labeled "Fan Thermo Switch", down near where the fan is plugged in and tried grounding that. It sparked and nearly burnt my finger doing so. Now I'm thinking I've got a relay problem. I swapped the horn and fan relays, horn works fine, but still no fan. I even took a spare battery I have and hooked up the fan directly to 12vdc and it works great. I wish the RF schematic was more specific. It's more like a block diagram than a schematic. Anyway, I'm really puzzled by this issue. Considering the problem I had with the RF harness initially, I'm wondering if there is another issue.

Thoughts and ideas are appreciated.

[Papa]

You mentioned that touching the Fan Themo Switch to ground caused a spark. That tells me that wire is hot, which it shouldn't be. I'd start by confirming the fuse block wiring is correct at the relay.

[Wizbangdoodle]

After more troubleshooting, it just gets worse. Keep in mind that I had tested all my lights and turn signals before it went off to paint. The one thing I need to check is my underdash wiring. When I mounted my rear view mirror, I had to loosen up the dash to get my hand up there. Even with that, it was a very tight fit and I may have loosened something. I don't think so, but you never know.

I pulled my fuse panel down and found my fan fuse blown. Also found my turn signal fuse blown. Replaced both, but when I try turn signals, it blows immediately. Must have a short to ground somewhere.

With all good fuses and the key on, I get 12vdc on the blue wire for the fan and the green wire for the thermo switch. When I plug the fan in, I can hear the relay click. I'm now thinking I may have to pull the dash out.

[Railroad]

Your relays may be wired incorrectly. The ground wire used to activate the relay, should not be under enough load to get hot.
Good luck,

[Wizbangdoodle]

Ok, it seems I created one of my own problems. I had dropped my fuse panel down to check it and that lost my ground. This caused my turn signals to quit working/blowing fuses. Once I grounded that, turn signals work fine.

So now I just need to verify that my fan works correctly. Shouldn't I be able to ground my green "Fan Thermo Switch" wire and the fan kick on? Bacause mine doesn't.

[Papa]

Ok, it seems I created one of my own problems. I had dropped my fuse panel down to check it and that lost my ground. This caused my turn signals to quit working/blowing fuses. Once I grounded that, turn signals work fine.

So now I just need to verify that my fan works correctly. Shouldn't I be able to ground my green "Fan Thermo Switch" wire and the fan kick on? Bacause mine doesn't.

Do you have +12v on the relay socket for pins 30 and 86 in the fuse panel? If yes, completing the ground to pin 85 should turn power on for pin 87. If this all checks out and the fan still isn't coming on, it could be the relay or a problem in the wiring itself.

[Nigel Allen]

With the ignition on, tap the green thermo fan wire against a ground. You should hear the fan relay click on and off as the ground circuit is made / broken.
If relay doesn't click, swap it with the horn relay and test again. If it still doesn't work then most likely you have some sort of wiring fault.
If the relay does click and the fan doesn't run then you either have it blown fuse faulty fan or wiring issue. A multimeter can really help from here.

Best of luck,

Nigel

Extra note:

From rereading your initial post. You said that when you plug the fan wires into the cooling fan, you hear the relay click. This shouldn't be the case. It's almost like the fan wire and the sense wire that goes to the temperature switch are reversed. I don't have specific experience with Ron Francis wiring kit as I did my own custom loom, but something is seems wired incorrectly from what you are describing.

[Wizbangdoodle]

Do you have +12v on the relay socket for pins 30 and 86 in the fuse panel? If yes, completing the ground to pin 85 should turn power on for pin 87. If this all checks out and the fan still isn't coming on, it could be the relay or a problem in the wiring itself.

Thanks for the reply Papa. I'd love to know where these numbers are. I've looked over the "schematic" and the fuse panel and there are no numbers on anything. Are 30 and 86 the coil wires? And 87 is the 12vdc output to the fan?


With the ignition on, tap the green thermo fan wire against a ground. You should hear the fan relay click on and off as the ground circuit is made / broken.
If relay doesn't click, swap it with the horn relay and test again. If it still doesn't work then most likely you have some sort of wiring fault.
If the relay does click and the fan doesn't run then you either have it blown fuse faulty fan or wiring issue. A multimeter can really help from here.

Best of luck,

Nigel

Extra note:

From rereading your initial post. You said that when you plug the fan wires into the cooling fan, you hear the relay click. This shouldn't be the case. It's almost like the fan wire and the sense wire that goes to the temperature switch are reversed. I don't have specific experience with Ron Francis wiring kit as I did my own custom loom, but something is seems wired incorrectly from what you are describing.

Thanks Nige, most of my problems have been self inflicted, but if I had a proper schematic, it would have made life much easier. I swapped relays early on in my troubleshooting and it checked ok. I even pulled it out and put it on my bench power supply and ohmed it out while operating it, all ok. I'll give this another go in the morning and see what I come up with.

[Fixit]

30 = Relay Common
87 = Relay N.O.
87a = Relay N.C.
85 = Coil Neg.
86 = Coil Pos.

[CraigS]

Since a lot of this started after going for paint, and I assume that all the lights were removed, I'd be looking at light wiring first.

[tnt_motorsports]

Thanks for the reply Papa. I'd love to know where these numbers are. I've looked over the "schematic" and the fuse panel and there are no numbers on anything. Are 30 and 86 the coil wires? And 87 is the 12vdc output to the fan?


These numbers are on the relay themselves. If your relay doesn't have the numbers printed or inscribed on it, they can easily be found online in reference materials.

[weendoggy]

Fixit has the correct layout, although some people change 30 and 87 opposite of industry standard. You need to check that. Also, don't really need to use 87a on your setup. Here's a simple diagram...

224507

If you want the relay to be "hot active" 100% of the time, just jumper between 30 & 86 and not use the ignition to 86. This makes the relay work even with key OFF (unless you have a battery disconnect) and only if the ground is complete (engine temp above sensor). Wiring per the diagram will only work with key ON.

[Wizbangdoodle]

Solution!

Once again, F'd by the RF wiring harness. I know that I should have gone through this harness with a fine tooth comb before the body went on, but time did not allow that. If someone offered me a free RF harness, I'd spit in their face.

The 6 wire connector that has the horn, left front turn signal, fan thermo switch, cooling fan, right front turn signal and right parking light is the culprit. Of these 6 wires, 3 of them are green. They also don't label the wires on the front harness. Someone needs to tell them that there are more colors out there. So I rang out each wire and re-wired the plug properly and now it all works.

I'm so pissed about the lack of QC from RF. It's almost like someone is asleep when putting these together. And, of course, they'll just shrug and say oh well. :mad:

[Papa]

I'm glad you got it figured out and agree that RF has had some serious quality escapes. I went through mine to confirm all the wires had continuity on each wire in each of the separate harness sections and also confirmed the wires were aligned with each mating plug. I didn't find any issues with my harness, but there may still be a few surprises waiting that I haven't identified yet.

[Nigel Allen]

It's excellent that you have the electrical skills and equipment to suss it out. Great outcome, but pretty poor on RF's quality control.

Onward and upward!

Cheers,

Nige

[Wizbangdoodle]

Thanks guys. It just baffles me how they could get this so wrong.

One of my customers used to be Genie Lift. When I would walk through the wiring department, they had boards laid out with diagrams painted on them. There were pins on the board so they could route the wires around them and get the right length. Once the harness was put together, they had a test jig made up so all they had to do was plug in the harness to the jig and it checked all the connections. I think because of this, I did not suspect that a wiring harness could be so screwed up. Oh well, like Nige says, onward and upward.

My other project is a '67 F-100. I bought an American Autowire harness for it. You can be sure I'll be checking it very closely.

[rich grsc]

I used American Auto wire, was completely happy with it. Why has Factory Five not addressed these issue with RF?

[Wizbangdoodle]

I used American Auto wire, was completely happy with it. Why has Factory Five not addressed these issue with RF?

Good question Rich. If it were me, I'd be looking at another supplier. This hasn't just happened once or twice or short lived. We've been hearing about bad harnesses for years.