Topic: 1967-68 Safety Convenience System - Application, Components, Wiring, Lenses and Bulbs

[ruppstang]

I think it may have been a prototype car. I have a original Ford option sales catalogue that states that if AC is added and the convenience group is ordered a floor console must be too. I have seen service parts for the park brake reminder but not Door agar or low fuel.
I find it very odd on a loaded car like this there was no floor console. May have been early enough the console was not ready. I wish the photos were colored and bigger.
Marty

[67gta289]

I concur with Marty, and discount quite a bit of what I see.  The confusing thing is why this took till January 67 to be published.  They were a little behind the 8 ball.

Regarding the "article", that is why I posted the pictures.  I will continue to search and document items pertaining to this option.  Picked up another 68 harness recently also.

[mikelj5S230]

An interesting thread, here is a picture of mine, it is on a late April '67 built Jersey GT 'vert.  My Low Fuel and Seat lights are not working.  I see about what may be wrong with the Seat light, but for the Low Fuel, I am assuming there was a special fuel tank sending unit?  Mine only has one wire coming out so assume it is not correct.  Anyone know if they make these or used/NOS is the only route?

[ruppstang]

NOS or original is the only way. Originals can be repaired.

[67gtasanjose]

Anyone know if they make these or used/NOS is the only route?

A seller has had this listing for several months now going:
http://www.ebay.com/itm/1967-1968-Mustang-Cougar-Fuel-Sender-with-Low-Fuel-sensor-RARE-/281419583343?pt=Vintage_Car_Truck_Parts_Accessories&hash=item4185ea0f6f&vxp=mtr

Often the thermistor on them is bad for the low fuel indicator. The thermistor is available aftermarket almost anywhere now.

You can get the sub-harness with the two wires for the fuel sender from Scott at West Coast Cougar, it is 67 only though 68 will fit. (Cougar is the same, 67 and again for the 68's though the covering is different)  If your tailight harness is correct, that single wire coming off your fuel sender should have some sort of plug or possibly a splice into where a double wire connector under the trunk mat should be. This is assuming the tailight harness is original or the option is original to your car. Hard to say so many years down the road what else may be defective, but there is a relay attached to the wiper motor for the Low Fuel light, but I don't think it ever goes bad.

Richard

[krelboyne]

The seat belt reminder is connected to a relay, and it has a Ford number of C7AB-10B924. Basically just a momentary illuminated light at start up. Not connected to a pressure switch or to a wire in the seat belt like later years.

We (WCCC) have not had a low fuel sending unit for a 1967 XR7 for a while now. They are different from the equivalent 1968 sending unit. Smaller diameter tube 5/16 for 1967 and 3/8 for 1968, just like the hard fuel lines.

The thermisters just didn't last, but maybe 5-8 years. There is an Electronic Low Fuel indicator available, it works off of the fuel gauge.

[midlife]

The low fuel relay uses a very strange resistor wire, whose value is not documented well.  Of the three I've seen across my bench, all three wires were broken and are so fragile that they cannot be repaired. 

I'm not sure it is worth the aggravation to get that system up and functioning correctly---it is extremely rare and finicky.

[ruppstang]

You are correct a complete working system took me almost two years to complete. Nock on wood it is still working six years later.

[mikelj5S230]

Thanks all, I have ordered the wiring from Don at WCCC, and the sending unit from John's Classic Cougars.

[67gtasanjose]

The low fuel relay uses a very strange resistor wire, whose value is not documented well. 

My harness is out of the car and I can test this wire's resistance. (I'll try to remeber to take my DVOM home tonight) It might be good data for this thread. John @ 67gta289 might have some out also, I believe even had mentioned having a 68 harness maybe. It would be good to know. Maybe the resistor wire could be replaced with just an ordinary resistor (if the wire failed) It cannot be exactly Rocket Science...mankind hadn't (allegedly) made our way to the moon yet when these were developed (circa 1964?)

Richard

[jwc66k]

It is called a thermistor which is an electronic term for a temperature sensitive resistor. It looks like a small capacitor with a metal shell and one or both leads coming from the same end. When the gas tank is more than 1/4 full (empty), the thermistor is submerged in gas which keeps it cool and the resistance is high. When the gas level is lower that the thermistor, it warms up and the resistance is low, the low fuel light goes on. There is no substitute. - http://www2.cougarpartscatalog.com/fm-ef008a.html - It's about $35.
Jim

[67gtasanjose]

It is called a thermistor which is an electronic term for a temperature sensitive resistor. It looks like a small capacitor with a metal shell and one or both leads coming from the same end. When the gas tank is more than 1/4 full (empty), the thermistor is submerged in gas which keeps it cool and the resistance is high. When the gas level is lower that the thermistor, it warms up and the resistance is low, the low fuel light goes on. There is no substitute. - http://www2.cougarpartscatalog.com/fm-ef008a.html - It's about $35.
Jim

Jim, we were last talking about the resistor WIRE located in the Convenience Control Harness at the relay. It is a cloth or fiber-coated frail wire that initially Randy (Midlife) brought up as a problem area. Discussion was on it's resistance value.

Richard

[jwc66k]

Jim, we were last talking about the resistor WIRE located in the Convenience Control Harness at the relay. It is a cloth or fiber-coated frail wire that initially Randy (Midlife) brought up as a problem area. Discussion was on it's resistance value.

Ah, I see it as the jumper between the 365A and 367 wires in the connector of harness C7ZB-10C877-A at the low fuel relay on the 67 wiring diagram. It jumps 12V from the ignition switch switched power and the thermistor lead from the tank. It looks like it's part of the "lamp test" circuit. As a resistance wire it would not be much, 5 to 10 ohms estimated (maybe less), judging from the length in the assembly drawing. It would approximate the low resistance of a low fuel level resistance from the thermistor so you would see if the lamp worked. (See my previous on how a thermistor works. There will be an open book test on Tuesday.)
Jim

[midlife]

That sounds about right, but I seem to remember readings about 45 ohms, or perhaps that was the specification for a similar application but a different Blue Oval product.

[67gta289]

I had a few minutes to dig out the 67 parts, not the 68, but suspect no real difference.

Picture 1 below is of the resistor wire.  This is the white dotted wire that is a short jumper (about 10") that parallels the low fuel relay coil.  The resistance is 46.4 Ohms (not bad, Randy).

Picture 2 is a quick schematic I put together.

The thermistor, when submerged in fuel, is effectively cooled off due to heat transfer, keeping the low fuel relay de-energized.

When the level is low, the thermistor heat transfer drops due to a change from liquid to air, resulting in the thermistor heating up.  As the thermistor heats up, the resistance drops enough to cause the low fuel relay to energize, which closes the contact to the low fuel lamp.

I found two sending units, a C7 and a C8.  In both cases they are an open circuit.  Before picking up another, I'll set up an experiment with potentiometers and running the system at 13VDC to determine when the relay energizes and de-energizes from a thermistor resistance perspective.

It could be that with no potential, the thermistor is completely open. 

Also in regards to the resistor wire, if you are considering replacing the wire with a resistor, I calculate 4.2 watts.   Technically a 5 watt resistor would handle it, but you have to consider the surface temperature of the resistor, and what is in proximity that can melt and catch fire.  If you look at the wire, the heat is over the 10" length rather than a contained area of a resistor.  Also the wire is covered most likely with an asbestos wrap for insulating purposes.  If I had to do something along these lines, I would go with a 10W 47 ohm wire wound resistor, and connect to a metal bracket (such as the "Z" bracket) to promote heat transfer, and make sure all other wire and plastic is at least an inch away.