The Ford Barn

gearheadbill · 12-09-2017, 09:57 PM

What I want to know is where exactly, in the engine bay of my 40, the black wire that runs between the temp sensor and the temp gauge exit the factory cloth covered wire loom?

I need to cut into the cloth covering to discover where the wire is but don't want to expose more of the individual wires than I must. Said black wire IS connected to the gauge, DOES directly enter the larger under-dash loom and presumably out thru the firewall into the engine bay. But it disappears. No tag end to be seen. Seems to have been cut off at some time. I'm trying to preserve the original wiring looms as much as I can while getting the temp gauge connected. I hope this question makes sense. Thank you.

Lawson Cox · 12-09-2017, 10:31 PM

On a 35 that "wire" is a copper tube, with a coiled wire " wrapped around it, that runs from the sensing unit in the head to the red liquid filled tube in the dash gauge.) It is not wrapped as part of the wiring harness, That is unless I am missing your point completely. Same set up on most early Fords,

gearheadbill · 12-09-2017, 10:37 PM

Lawson: 1940 coupe...not 35. Thank you

JSeery · 12-09-2017, 10:48 PM

Well, the temp sender wire should be bundled with the generator wires and coil wire. You would need a photo if you wanted the exact exit location. Maybe someone with a 40 could post a photo. Kube would be a good source of information.

Terry,OH · 12-10-2017, 06:46 AM

Three wires in the cloth covered harness loom. The red for the coil and the BY for the oil pressure and the black for the temp sender. The B wire exits the wire harness just above #7 plug. The 3 wire harness loom joins with the wire harness loom for the starter solenoid at the firewall near the metal wiring clamp on the firewall and form one larger loom going into the kidney shaped metal cover .

JSeery · 12-10-2017, 08:32 AM

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Terry, the generator to regulator wires are not it the same loom? Are they separate?

JSeery · 12-10-2017, 08:42 AM

Here is a photo (not mine) of a 47 harness. Not sure it is much help for a 40.

gearheadbill · 12-10-2017, 03:57 PM

here are some pics...thanks.

gearheadbill · 12-10-2017, 06:56 PM

I think I've solved 'my mystery'. JSeery posted that the missing wire would have been bundled with the oil pressure, coil and generator wires. I believe that is correct, in that there is a black wire in that bundle but mostly hidden because it had been butt-spliced into a solid red wire. The referenced black (and then red) wire was attached to the GRD post on the generator. I have now routed it to the pass head temp sensor and checked continuity with the gauge. BINGO.

This brings up another question for me. What is the purpose of the GRD stud on the side of the generator if no wire is routed to it? I've attached pics. Thanks for your patience AND knowledge.

JSeery · 12-11-2017, 12:16 AM

This was a transition period. Ford switched from just using a cutout to using a voltage regulator. The first wiring harnesses after this change did not include a ground wire between the generator and the voltage regulator. By 41 this ground wire was added and is included in all year there after. The function of the generator/VR system is improved with the dedicated ground wire. During this transition period I have no idea of the actual dates of the changes.

deuce_roadster · 12-11-2017, 11:22 AM

The temp sender should be in the LH head (driver's side US model) Hot water heater shutoff valve in RH head or plug. Correct heads for a 40 only have one tapped hole in each one and come in a pair 81A-6049 and 81A-6050 (part numbers visible back by fuel pump stand)
Since you want originality regarding the wire I thought you might want to know where the sender should be located. And as Jseery stated your generator is a later one, the 40 has only 1 stud on the side and should have U stamped in the case.

12-09-2017, 09:57 PM	#1
gearheadbill Senior Member Join Date: May 2010 Location: Snohomish, WA Posts: 401	wiring help question please What I want to know is where exactly, in the engine bay of my 40, the black wire that runs between the temp sensor and the temp gauge exit the factory cloth covered wire loom? I need to cut into the cloth covering to discover where the wire is but don't want to expose more of the individual wires than I must. Said black wire IS connected to the gauge, DOES directly enter the larger under-dash loom and presumably out thru the firewall into the engine bay. But it disappears. No tag end to be seen. Seems to have been cut off at some time. I'm trying to preserve the original wiring looms as much as I can while getting the temp gauge connected. I hope this question makes sense. Thank you. Last edited by gearheadbill; 12-09-2017 at 10:38 PM. Reason: spacing, clarification

12-09-2017, 10:31 PM	#2
Lawson Cox Senior Member Join Date: May 2010 Location: Above the gnat line in Georgia Posts: 7,009	Re: wiring help question please On a 35 that "wire" is a copper tube, with a coiled wire " wrapped around it, that runs from the sensing unit in the head to the red liquid filled tube in the dash gauge.) It is not wrapped as part of the wiring harness, That is unless I am missing your point completely. Same set up on most early Fords, __________________ Life is like a roll of toilet paper. The closer to the end, the faster it goes. It is better to be seen, than viewed. "We sleep safe in our beds because rough men stand ready in the night to visit violence on those who would do us harm".

12-09-2017, 10:37 PM	#3
gearheadbill Senior Member Join Date: May 2010 Location: Snohomish, WA Posts: 401	Re: wiring help question please Lawson: 1940 coupe...not 35. Thank you

12-09-2017, 10:48 PM	#4
JSeery Member Emeritus Join Date: Nov 2012 Location: Wichita KS Posts: 16,132	Re: wiring help question please Well, the temp sender wire should be bundled with the generator wires and coil wire. You would need a photo if you wanted the exact exit location. Maybe someone with a 40 could post a photo. Kube would be a good source of information.

12-10-2017, 06:46 AM	#5
Terry,OH Senior Member Join Date: May 2010 Posts: 4,751	Re: wiring help question please Three wires in the cloth covered harness loom. The red for the coil and the BY for the oil pressure and the black for the temp sender. The B wire exits the wire harness just above #7 plug. The 3 wire harness loom joins with the wire harness loom for the starter solenoid at the firewall near the metal wiring clamp on the firewall and form one larger loom going into the kidney shaped metal cover .

12-11-2017, 12:16 AM	#10
JSeery Member Emeritus Join Date: Nov 2012 Location: Wichita KS Posts: 16,132	Re: wiring help question please This was a transition period. Ford switched from just using a cutout to using a voltage regulator. The first wiring harnesses after this change did not include a ground wire between the generator and the voltage regulator. By 41 this ground wire was added and is included in all year there after. The function of the generator/VR system is improved with the dedicated ground wire. During this transition period I have no idea of the actual dates of the changes.

12-11-2017, 11:22 AM	#11
deuce_roadster Senior Member Join Date: Oct 2011 Location: Shelton, WA Posts: 3,800	Re: wiring help question please The temp sender should be in the LH head (driver's side US model) Hot water heater shutoff valve in RH head or plug. Correct heads for a 40 only have one tapped hole in each one and come in a pair 81A-6049 and 81A-6050 (part numbers visible back by fuel pump stand) Since you want originality regarding the wire I thought you might want to know where the sender should be located. And as Jseery stated your generator is a later one, the 40 has only 1 stud on the side and should have U stamped in the case.