I am trying to incorporate both the factory optional oil pressure gauge and the oil idiot light into the custom cab dash of my '66. The wiring diagram shows the sending unit going to the gauge and the constant voltage unit supplying power to the gauge. I may have the incorrect sending unit because I seem to measure either 15 ohms or 30 ohms across the sending unit where I would expect to see a linear variation from a dead short to open. When I use an oil pressure switch, the idiot light works (comes on) below about 5 PSI. Does anyone else have both factory options (non-mechanical & idiot combo)?

 

C5TZ9B339B .. Fitting ~ Use with Oil Pressure Sending Unit Switch and Oil Warning (Idiot) Light Switch / Obsolete

ANTIQUE AUTO SUPPLY in Arlington TX has ONE = 817-275-2381.

JST AUTOMOTIVE in Lebanon TN has ONE = 615-443-3086.

B & L Ford in Ashland PA has TWO = 570-875-4417.

GREEN SALES CO. in Cincinnati OH has TWELVE = 800-543-4959.

Fits: 1965/67 F100/350 240/300/352.

This is a splitter type fitting, made so both sending units can be installed.
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E4ZZ9278A .. Oil Pressure Sending Switch (Motorcraft SW1547B) / Use with Oil Pressure Gauge / Available from Ford.

Fits: 1957/96 Cars/Trucks/Bronco's/Econolines / E4ZZ9278A replaced: D9ZZ9278A, C9ZZ9278A, C7ZZ9278A and B7T9278A.

 

May check with local auto parts store, purchase both the warning, and gauge sending unit from local NAPA parts store. There's an adapter for mounting both sending units, should be able to salvage one, I have not bothered, used 1/4" threaded steel pipe, found the brass too fragile, approx. 3' long and added a 't' connector and both been working great for past several yrs. Ran a solid wire from the respective sending units to the warning light, and gauge then connected the other side of gauge/light thru the CR unit, where current oscillates from 0-9 volts.

 

I need to buzz out the factory wires to the gauge and see where they end up. They have the same colors as the light yet there is only one wire running through the bulkhead connector (white-red) that is being used for the oil switch.
I have what I believe to be the correct switch and sending units (both new but aftermarket) but there are no numbers on the sending unit. Is the constant voltage unit supposed to be 12V? I thought it was supposed to be around 6V.

 

Here is what the set up looks like. The small unit is for the idiot light and senses oil pressures less than 8 psi. The large unit is for the gauge and can handle pressures to 100 psi. To make my gauge work, since I am a '65, I spliced into the power wire running from gauge to gauge behind my dash. Hooked up the white w/red tracer wire to the back of the gauge and it worked. When I start the truck the idiot light comes on momentarily and then goes out. My gauge then registers about 60 psi while the truck warms up.

 

As is the case with most problems that seem complicated I appear to be chasing multiple issues at once. First, thank you Mike for the picture and that is the approach I am taking - except right now I have an air compressor and regulator providing my test pressures.

I have found that the dedicated wire for the gauge just stopped inside the factory harness! I pulled back the original electrical tape - and I say that with confidence because over the top of the tape is the tag C5TB 10A665E WCC - and the wire was cut right in the middle of the harness. And the electrical tape was one contiguous piece - all the way to the end at the gauge and the terminal lugs.

I'll keep you updated as I discover more.

 

Found yet another wire which was bad. External appearance was good but resistance was way too high. I have completely bypassed this wire and have the gauge working but I can say it doesn't appear to be very accurate above 20 lbs. Off by 20 lbs at 80 lbs pressure. But that factory gauge really looks nice! I will post a pic when I wrap this up - literally.

 

ND,
Is there a similar part that would fit on a '63 F-100 with a 292? A previous owner put in an aftermarket pressure gauge and disconnected the 'idiot' light. I would like to make the same setup.

Jay

1963 F-100 2wd/292
"When neck deep in shi*, don't duck!"

 

And still I found more bad wiring. The problem with the sending unit was trying to measure in-circuit resistance. If I set it up on the regulator by itself the resistance would be linear - as expected. If I measured in-circuit I would measure 15 to 30 ohms.

And I also took the opportunity to clean up wiring both behind the instrument cluster and under the hood. This involved a complete rework of the ammeter wiring at the solenoid because the PO had the ammeter configured such that it could only measure the load of current, not the charging. Without a detailed diagram I can only tell you this put the starter in the circuit and an excessive load on the ammeter during cranking. I had to build a terminal block to bring the alternator battery terminal and the positive side of the ammeter gauge together without tying it into the solenoid.

Nice bright dash lights. Working ammeter and oil pressure gauges. Working idiot lights for ALT & OIL. These are a few of my favorite things...

 

Don't feel installing a thermal block in the alt circuit is a bad thing. Replaced the instrument cluster on the 65 but did not get around to connecting the alt gauge for few yrs. Concerned about that much amps going to the instrument panel and was not sure how to hook it up. FTE member made a drawing and emailed a copy of the circuit, took a matter of couple hours to install. Just had to move a wire from batt. side of starter relay, and place a fuse block in the circuit.

IMG]http://i300.photobucket.com/albums/nn25/goatfarmer_photos/FordAmpWiringDiag.jpg[/IMG]

 

Don't feel installing a thermal block in the alt circuit is a bad thing. Replaced the instrument cluster on the 65 but did not get around to connecting the alt gauge for few yrs. Concerned about that much amps going to the instrument panel and was not sure how to hook it up. FTE member made a drawing and emailed a copy of the circuit, took a matter of couple hours to install. Moved a wire to one side of a fuse box and the other side of the fuse block to the alt gauge, works great.

 

The Ammeter should really be inline with the charging circuit. If you simplified the circuit the Ammeter would be between the BAT of the alternator and the POSITIVE terminal of the battery.

I do have one new "feature" now that the wiring is the way it should be. These alternators are only about 30 amps so if I have my AC on at idle with the blower on high, my headlights on high beams, my foot on the brake, and my turn signal on, My ALT light blinks just like my turn signal! I guess I found the limit of the output of the alternator!

 

Push in the cig lighter... I dare ya...

 

1/3/2017: Edited the quantity/sources.

 

Attempted to post pic's Photo Bucket Sucks!