1980 F350 4X4 C6 Project

[Atlas75]

I had a few moments today so I tested the gauge as you suggested.  My test light blinked in a consistent pattern when connected to the factory wire.  I also grounded the wire and turned on the key and the gauge moved.  So I think I am down to a bad sender or the connection between the sender and the factory wire (which is not to pretty).  Is there a resistance range that the sender should measure depending on the heat of the coolant?

[Atlas75]

I forgot I also had a question.  You can see the new unit mounted on top of the thermostat housing…which is on the radiator side of the thermostat.  My question is in regards to the blocked off port that is to the left and down on the intake manifold.  Does anyone know if that is coolant?  That would be a better place for the aftermarket gauge.

[Gary Lewis]

Yes 10 to 72 ohms.

[Atlas75]

I took a meter to the engine temp sending unit today.  I let the engine warm up just a bit and then shut the motor off and measured the resistance.  Looked to be a bit over 2M ohms.  I think a new sending unit is in my future as that is no where near a range of 10 to 72 ohms.

[Gary Lewis]

I think you've found it.  

[Atlas75]

Quick radio question.  My truck has a Motorola radio.  Not sure if it is original or even a ford radio.  It is model 5F3RMX8.  My question is in regards to the connections.  It has 3 wires (not including speakers).  A white, a white with red strip and a black.  The black is cut so it is not doing anything.  How should it be connected?

[Gary Lewis]

That model # doesn't show up in the master parts catalog, so I don't know anything about it.  And the wire colors don't match anything in the 1981 EVTM, although I've not looked at the 1980 EVTM.

But I'd bet the black wire is ground and the white or white/red is switched power and always-on power, or vice versa.  I would pull that cover and see if it looks like the black wire goes to the chassis.  Or use a DVM to check that.  If so I'd put power to both white and white/red and speakers to the others and see if it works.  If so, then experiment to see if white or white/red is switched.

[Atlas75]

Why would you need an unswitched supply to a dial radio?  

[Gary Lewis]

Good question.  

So, one is probably illumination?

[Atlas75]

Good thought!  I’ll try to test for that.

And I did learn that that model radio was used in Ford vehicles up through 1978.

[Atlas75]

You are correct!  The white/red is illumination only.  The white is power.  The black is still a bit of a mystery.  The chassis is clearly the ground.  The black connects to the same rheostat (but not the same terminal) that the power does.

[Gary Lewis]

You do have a separate antenna connection, right?

If so, I can't imagine what the black is.  I see then soldered connection to the case for ground, but I also see the orangeish looking wire coming from the feed-through terminal the black wire connects to the other end of, so it must not be ground.  

[Atlas75]

Yes, I do have a separate antenna connection.  Not knowing what this came out of, is it possible it is a power antenna trigger?  Did power antennas exist in the 70’s?  That is the same rheostat that turns the power on for the radio so maybe it sends out a signal to raise the antenna.  Thoughts?

[Gary Lewis]

Yes, it could be a power antenna connection.  I would put my DVM in ohms mode and connect one lead to white and one to black and turn the switch on.  If it is a power antenna lead you'll see the resistance go to almost zero.

[Atlas75]

Bingo!  No connection with power off.  Zero ohms with power on.  Thanks Gary!

[Gary Lewis]

You did it, not me.  

[Atlas75]

It takes a village!

Just to test a few things I hooked up the radio and used a wire to ground the case to the vehicle.  The radio would not turn on.  Not until I plugged in the antenna wire did the radio come to life.  Not sure what's up with that.  One more layer of the onion that needs to be peeled!

[Gary Lewis]

The antenna is grounded and so would bring a ground down its lead.  Perhaps your ground didn't work?

[Atlas75]

Hey Gary, on a previous post you indicated that my temp control cable for my heater was part number E0TZ-18518-A as shown below.



I finally pulled the cable out and found a small tag wrapped around the cable that says E0TH-18D306-AA.  Why the difference between the two numbers?  TIA

[Gary Lewis]

Some place I need to document this 'cause I have to keep telling people about it since it is so bizarre.  But any # on a part is not a part #.  Does that make sense?  It doesn't to me.  

In the 60's Ford had one of their Better Ideas, and I think it says a lot that it was in the 60's.  

But the idea was that they'd put ID #'s on the parts and part numbers in the Master Parts Catalog.  Then they published a Master Cross Reference List where both are listed.  I have three of those cross reference books, and the 1980 version thereof is 1228 pages long.  

And, sure enough, ID # E0TH-18D306-AA cross references to E0TZ-18518-A.

One tipoff that you are looking at an ID #, other than it being on the part, is that the prefix should be something like E0TZ and not E0TH.  Another is the double-character suffix like -AA.  Part numbers, from what I see, never went to more than one character.  But ID #'s had both single and double-character suffixes.