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

[tomnorman457]

There are actually three temperature sensors for our 88 Festiva L.

Two are on the engine block; one is the temperature gauge sender, and the other turns the cooling fan on and off.

The third temperature sensor, on the bottom of the radiator, sends a signal to the engine computer. What happens with that signal is beyond my skill-level.

[Safety Guy]

Interesting information!

I'll have to have another look at my '89L radiator. As far as I know it's the original one.

Karl

[WmWatt]

The sensor at the bottom of the rad is not mentioned in the Haynes instructions for replacing the rad. Only two coolant sensors are shown on the wiring diagram and they are both shown in photos (Chapt 3, cooling and air conditioning) as being on the engine, not the rad. Confirms Tom Norman's observation is it is an undocumented bonus feature of the vehicle. Try Microsoft support?

[Occhty]

Little more info:

The radiator temp sensor has two wires,

1: Lt green
2: Black

The thermostat housing sensor, one wire.

1: green with red stripe

And the block sensor, one wire

1: either tan or lt brown

[drddan]

Wrong thread, removed post! Ha!

[XFSE71]

see this page for info about the Engine Coolant Temperature Switch.
http://www.fordfestiva.com/forums/sh...Name-that-part!

[200KGPGTP]

The radiator I got a while back was off of a carby and it has the rad temp sensor. Obviously, I won't be using it in my car, No need for it. But the rest of the rad appears identical, so I'm good!

[bravekozak]

Can someone please take a pic of a copper rad. I thought they were all made of plastic. If the top and bottom reservoirs are copper or brass, I would be willing to buy one from anyone who has an old one lying around.

[1990new]

I just ran across this while trying to figure out why my friend Sam's 1988 Carb 4 speed radiator fan would not come on.
It has that extra sensor that screws into the radiator. Anyway I discovered that if I disconnect the wires from both sensors the fan will come on and run all the time.
Are the two sensors different? Sam wants me to order an new sensor that screws into the radiator but I can identify which one it is on Rockauto,

[bravekozak]

I have an NOS rad sensor for sale.

[1990new]

I have an NOS rad sensor for sale.

PM'd

[needragr]

So I also have a "disabled" coolant temp circuit, in other words, the sensor at the thermostat housing & the sensor in the (copper) radiator are both failed or disabled, as soon as you have key on, the fan comes on.
I suppose it could be worst but Id rather fix it.
I pulled the one out of the head, single pole connector & it protrudes just behind the thermostat when installed. It has a 7C stamped on it.
The "switch" in the bottom of the rad is a two pole, so what conditions should I measure for? IE at what temp does the switch supposed to open or close (?) sending a signal back to the ECU and what is the single pole head sensor doing?

Does anyone have the correct test & values (resistance /temp) that these sensors / switched are too see?

[william]

The one that controls the fan is the one in the tstat housing.
Ground that wire and if the fan shuts off its your switch.

[tooldude]

The Radiator Temperature Switch should have open contacts below 63*F and closed contacts above about 63*F. It gives a signal (ground) to the ECA which affects air fuel mixture, and on the carbureted engine, the EGR control.