Mechanic's opinion needed...

[Ark]

The connector to the coolant sensor SHOULD energize the cooling fan when a jumper is inserted between the two contacts - but it does not. One wire IS energized even with key off, the other is ground.

The cooling fan controller is supposed to energize the fan whenever the A/C is “on”, and at anytime coolant temperature exceeds spec’d limits - regardless if key is on or off. It does not.

This one has me tearing my hair out, what’s left of it.

My Ford Shop Manual says that the cooling fan controller is located behind the glove box insert - convenient, huh?

It’s not there … so tomorrow is going to be a royal PITA.

That's why my idea was to jump the hot lead on the coolant sensor connector directly to a good chassis ground. Maybe that ground lead has gone bad somewhere. You're right, if that connector does have a path to ground then it should activate the relay and fire the fan right up. So maybe it doesn't?

The fan controller not turning it on with the AC is interesting. The fan does come on when you jump the fan relay terminals directly, right?

 

[Lmo1131]

Okay, I'm obviously NOT an electrical engineer, but here's what I observed this afternoon;

The coolant sensor, in the block, closes at a pre-determined temperature and connect the 12.3 vdc line to ground... why is there not a monumental flash as + meets -?

A jumper applied between the 12.3vdc and the ground of the connector does nothing; no sparks, no fan. Zip, nada, gooseegg.

However if the connection at the inline resistor is grounded (at the red arrow), the fan turns on... which is what is supposed to happen. But I've never had much luck connecting a "+" wire directly to a "-" wire (except when MIG welding).

I have not been able to test the coolant temp switch to determine if it is opening/closing.
But at this point I think the Coolant Temp Switch Connector has failed (jumping pins has no effect).

I am, to say the least, confused.



I do not know what the component marked with ???, is. It is not labeled on the diagram. I would have expected it to be a relay. The only similar symbol I've found is for an "inductor". No clue what it does...

 

[Ark]

The coolant sensor, in the block, closes at a pre-determined temperature and connect the 12.3 vdc line to ground... why is there not a monumental flash as + meets -?

A jumper applied between the 12.3vdc and the ground of the connector does nothing; no sparks, no fan. Zip, nada, gooseegg.

However if the connection at the inline resistor is grounded (at the red arrow), the fan turns on... which is what is supposed to happen. But I've never had much luck connecting a "+" wire directly to a "-" wire (except when MIG welding).

I have not been able to test the coolant temp switch to determine if it is opening/closing.
But at this point I think the Coolant Temp Switch Connector has failed (jumping pins has no effect).

I am, to say the least, confused.

View attachment 307544

I do not know what the component marked with ???, is. It is not labeled on the diagram. I would have expected it to be a relay. The only similar symbol I've found is for an "inductor". No clue what it does...

View attachment 307546

So either the resistor or connector has gone open. Did you jump right above the resistor to a chassis ground, or to the ground side of the connector?

Do you have continuity from the top of the resistor to the terminal in the connector? Maybe the solder or crimp job on that resistor just went out.

I think that ??? Symbol is the coil inside the fan relay. When energized, it pulls and closes the switch inside the relay.

 

[Lmo1131]

I’ll report back tomorrow after I’ve checked that set up.

 

[Mr. Habib]

Someone mentioned using a DVOM (volt meter) to sweep the TPS. Yes, that is a test method. However, you have to sweep it super slow or you can miss the bad spot in the sensor.

An analog meter like a Simpson 260 works much better for this kind of test. And yes, I am that old.

 

[thunderchicken]

An analog meter like a Simpson 260 works much better for this kind of test. And yes, I am that old.

I've been told several times over the years an analog meter is better for sweep tests. However, I don't need to perform that type of test enough to justify the expense. I've borrowed my brother's before and can say it picks up what digital misses