"Mystery" Green Wire Near Top Of Radiator, 1988 Festiva L

[tomnorman457]

While tracking down vacuum lines I noticed a green wire, almost two feet long, up towards the top of the radiator, on the driver's side. It was
electrical-taped to a black wire. The black wire goes to the front of the engine block, where it's attached, probably as a ground wire for something. But the mystery green wire is just taped off, connected to nothing.

I have been told that the carbureted 1988/1989 Festivas had an electrical radiator temperature sensor located at the bottom of the radiator, next to the radiator drain. This sensor fed a signal to the engine computer. Our radiator had been replaced prior to us getting the car. I crawled under the Festiva and found no such temperature sensor on the radiator. So we
probably have a radiator designed for a 1990 and newer, fuel-injected Festiva.

Anyways, I wondered if that green mystery wire was the wire that should be
connected to the radiator temperature sensor. (but we don't have one on this
radiator)

Does anybody know where that green wire goes and what that green wire was for?

Thanks, Tom

[WmWatt]

Mine is green with a white stripe. Plugs into something at the bottom centre of the rad. Haynes manual wiring diagram shows a light green wire to "coolant temp switch", black ground.

[tomnorman457]

I just looked at the wire again, and it's actually more "light" green than green. My problem is that there's no fitting on the incorrect radiator to install a new coolant temp switch. I wonder if I could insulate and metal tape a replacement temp switch (such as AutoZone SU405) onto the radiator somewhere? I know the sensor should be immersed into the coolant but that's not possible on this radiator. Or just connect the green wire directly to ground? I know these ideas are Mickey Mouse, but I'm looking for a work-around because somebody installed the wrong radiator with no fitting for the coolant temp switch. Thanks, Tom

[LoneManWolf]

well since my festiva died on me last night and is stuck at walmart parking lot right now... i can't be completely sure but i'm reasonably sure this goes to the coolant temp switch which isn't on the radiator but is located in the block just near the thermostat housing... only reason i say this is i recently had to replace that temp switch so
look for a metal prong sticking out of the block just to the left of the upper radiator hose or maybe slightly below it... wow my memory sucks
i could be wrong though lol

[Safety Guy]

Wolf's right. I looked at my 1989 Festiva shop manual and the fan temperature thermoswitch is located in the thermostat housing on your engine block corner at the engine end of your upper radiator hose.

I would have no idea what wire goes to the bottom of a radiator on our cars. This shop manual shows nothing like that, and I'm not familiar with any year of Festiva that has such a thing.

I also looked in my Haynes manual. Pages 3-2 to 3-5 neither show nor mention anything at the bottom of the radiator. Nothing in the pictures or text.

Maybe Mr. Watt has the weird radiator! (I'd take a close look at the fitting on that one and trace the wire if I were you.)

Since I cut off Muttstiva's front end, I no longer have a carbed reference "library," but I am sure there was no wire to anything but the fan motor on my '89 radiator.

Finally, I went out and looked at my '92L. The wire to the thermoswitch is green with a yellow stripe. The wire to the temperature sender (that goes to your instrument panel temp gauge) is all green. There are two black wires that look like grounds going to the engine block corner. That's all I can tell you about that, but it's possible, perhaps likely, that wire colors will be different between carby and FI even if those wires perform the same function.

Karl

[LoneManWolf]

well i just went and got my car running and brought it home
and yes that is the color of the wire on my 89 carbie
so it should be plugged onto the prong on the block near the thermostat housing
be aware that it might be unplugged for a reason
when testing that switch i read that if the relay is messed up, i believe but could be wrong, that unplugging that will allow the fan to run nearly continuously ... if the switch is bad and u plug it in it could cause the fan to shut off and not run.
That was the case with my car and i didn't want to have the fan running constantly as it just doesn't sound good for it.
So just be aware that it could cause the car to overheat and you should test to make sure nothing is wrong when u plug it in

[Safety Guy]

Yep, that's how it works. When the switch is bad, you can unplug it to allow the fan to run by default.

Karl

[LoneManWolf]

Yep, that's how it works. When the switch is bad, you can unplug it to allow the fan to run by default.

Karl

it's amazing what you can learn on this site
i know all of that b/c of the research i did and helpful people on this site who helped me through that little fiasco

[tomnorman457]

WmWatt is right on the money.

I bought a 1988 Ford Festiva shop manual, and I believe it addresses the question as to whether or not a switch/sensor exists in the Festiva radiator. Page 27-03-4 in the "Cooling System" section clearly shows a "radiator temperature switch". There's even a drawing showing the two wires that connect to the switch, which is screwed into the radiator, right next to the radiator drain.

[Occhty]

Yep, I have an 88 that has that switch, I've only ever saw it on the copper radiators. I'll get a pic tomorrow for y'all

[Occhty]

My sensor is missing a terminal prong, there should be two.

The radiator seems to look like a two core, I checked a few of my other cars and the single core radiators don't look thick enough to even try and install one. But my 90 automatic has a two core and a flat spot molded (plastic) in the same location as the copper radiator shown in the pic.

[Safety Guy]

I missed it in my shop manual the first time, but found that drawing of the "radiator temperature switch" on page 27-03-4. Weird!!

I also just realized my manual is for 1988. (I had thought it was 1989.)

Now on page 27-03-6 is another drawing showing the "cooling fan temperature switch" up at the thermostat housing. Huh?

Next I looked up the "instrument clusters and controls." On page 33-25-2 it shows the temperature sender bullet connector, with the cooling fan switch up above it.

What's going on here? I'm sure my '89L did NOT have a thermoswitch on the radiator. With the cooling fan switch on the t-stat housing, why would it be needed?

This is a mystery to me!

Karl

[tomnorman457]

Hi Occhty, thanks for the pictures. Now I don't feel so bad hunting down something that others say is not there. Are you having any drivability problems since your radiator temperature sensor is not connected? That sensor is supposed to send signals to the engine computer, so I wondered what effects you were having, if any. I've got a rough idle when cold, and surging/hesitation when it's warmed up. I've already done all the tune-up stuff to it, so it's not that. Thanks again, Tom

[Occhty]

I couldn't tell you, I've had that car sitting for about 5 years. It had a rod knocking and needed a motor. finally pulled a spare engine off the shelf and installed it last week. It starts and idles okay but i haven't finished hooking everything up, so I haven't drove it or run it long enough to find out yet. It's the only carby one I have and tends to get last priority. I should also add that it's inside a heated shop, the car thinks it's summertime.

[WmWatt]

Before posting the reply I went out to the garage, raised the hood, plugged in the trouble light, and looked. The green and black wires which are taped together at the top plug into a device at the bottom centre of the rad. My car is a carb'd '89.
There are two coolant temperature devices on the car. One is connected to the temperature guage on the dashboard. The other turns the fan on and off. One is near the thermostat. The other in the rad. I don't remember which is which. I'm typing this on a computer at the public library so have no way to look it up right now.