The Snakes Alive CMP Wiring Project

[Jacques Reed]

Hi Hanno,

Just looking at your picture there should be a wire, 30A, a jump from the oil pressure gauge brass bus to the Temperature gauge brass bus to supply current to the Battery and Oil Pressure gauges when the ignition switch is thrown.
There should be wire, 30, from the ignition switch to the Temperature gauge brass bus to supply current to the Temperature and Fuel gauges and then to the other gauges via 30A.

The wire into the Battery indicator is my concern. If it shows voltage only when the ignition switch is thrown then it is wire 30 and can be connected to the brass bus at any gauge to supply them with current. Diagram shows the Temp gauge but any brass bus is the same electrically.

If for some reason that wire into the Battery indicator shows voltage continuously it could be coming directly from the Battery via the regulator and therefore your wiring is setup for an ammeter. If that is the case it could cause a serious problem to the wiring and gauges if the Battery indicator is sent to earth. A quick check will determine if that wire is "hot" only when the ignition switch is on and therefore set up for a Battery indicator.

I have found with numerous owners over the years and many jury rigged wires on these vehicles it is best to check and double check. My first truck had many disconnected wires and even house wiring used in some places!

Cheers

[Hanno Spoelstra]

Originally Posted by Jacques Reed

Just looking at your picture there should be a wire, 30A, a jump from the oil pressure gauge brass bus to the Temperature gauge brass bus to supply current to the Battery and Oil Pressure gauges when the ignition switch is thrown.
There should be wire, 30, from the ignition switch to the Temperature gauge brass bus to supply current to the Temperature and Fuel gauges and then to the other gauges via 30A.

The wire into the Battery indicator is my concern. If it shows voltage only when the ignition switch is thrown then it is wire 30 and can be connected to the brass bus at any gauge to supply them with current. Diagram shows the Temp gauge but any brass bus is the same electrically.

If for some reason that wire into the Battery indicator shows voltage continuously it could be coming directly from the Battery via the regulator and therefore your wiring is setup for an ammeter. If that is the case it could cause a serious problem to the wiring and gauges if the Battery indicator is sent to earth. A quick check will determine if that wire is "hot" only when the ignition switch is on and therefore set up for a Battery indicator.

I have found with numerous owners over the years and many jury rigged wires on these vehicles it is best to check and double check. My first truck had many disconnected wires and even house wiring used in some places!

Hello Jacques, thanks for your guidance.

Currently the dash on my F15A is wired as follows:

• Live feed from ignition switch to BATT, strip connector to OIL pressure, then a wire runs (hence the double wire in the connector) from BATT to TEMP with a strip connector to FUEL.

I checked and the instruments are "hot" only when the ignition switch is in the on position. I have temporarily grounded the BATT meter (see the blue connector) and when the engine is running it slowly creeps up. Have yet to take it for a test drive to see if it is in the green at driving speeds.

IMG_7927.jpg

Indeed previous owners have fiddled with the wiring, hence my actions now to go through it, understand and correct it. It does not help the original covering has faded to a level where the colours are very hard to discern. Hence a rewire is scheduled for this winter.

For the upcoming event this weekend I have proper working indicators again, over the years they became dimmer and dimmer, with the old mechanical flasher relay, dash indicator light and bad connections robbing away 1.5 V from the 6 V available. With the connections cleaned up, dash indicator light omitted and an electronic flasher relay I now have the full 6 V supply to the indicator lights.

IMG_7930.jpg

[Ganmain Tony]

Where is the other end of your battery gauge ground wire connected Hanno?

[Hanno Spoelstra]

Originally Posted by Ganmain Tony

Where is the other end of your battery gauge ground wire connected Hanno?

Tony, my F15A has a ground stud under the dash, just above the steering column. That’s where I’ve grounded the flasher relay and the BATT gauge.

0F056C02-E497-4D55-8148-3EA3C9306F91.jpeg

[Ganmain Tony]

Thanks Hanno.
I will probably do something similar so it's good to see what other set ups look like.
Great to see your truck, nice example of an F15A.

[m606paz]

NOS wiring to install on my FGT. C39Q 14401 B. Thirth lamp socket for HI Bean indicator....

[Jacques Reed]

A recent discussion on another forum about the use of Radio Suppression condensers (capacitors) on the fuel senders got me thinking about the design of the fuel sender unit on a Ford.

It was suggested that the condensers served another purpose which was to reduce arcing at the contacts inside the sender as it made and broke contact in operation. This is similar to the use of a condenser at the ignition points. This could be desirable on a device fitted close to fuel vapor; however, I think this was not necessary and the designers, (King Seeley?) didn’t consider it as an issue with a well-sealed unit.

Interestingly the condensers were only fitted “as required”, and not a standard fitment to all CMP vehicles which implies the senders were designed so that any arcing at the bimetal contact is satisfactorily shielded from petrol fumes or liquid. There is also the hot heating wire for the bimetal arm to consider.

I thought I would open up a unit for a close inspection. I had one which I had condemned for a hole eaten through the casing. I made sure there is no liquid inside it by shaking it vigorously as I would be using a Dremel cut off wheel to open it up. Even 50-year-old petrol is flammable.

As the photo shows it has some identifiable parts from the operating diagram. Virtually everything inside attached to the bimetal arm is insulated from earth. There is an adjustment cam for factory setting the starting contact point on the bimetal arm. This cam is insulated from the bimetal arm by what looks like a Bakelite pin. The movable arm on the bellows is earthed as is all the sender casing.

The unit is sealed with a substantial rubber gasket. As far as fumes leaking into the sender, this could only occur if the bellows had a hole in it, or the tank side of the sender had a hole (my condemned one) or there was a hole in the outside of the sender unit and fumes got in, such as in a during refuelling. Ignition should be switched off in any case during refuelling.

So, I think there is a low chance of a fire caused by a sender as long as it is good condition and not suffering from corrosion, or damaged in a way that the internals are exposed to vapor. Having said that, I would have a good check of any fuel sender unit for signs of holes or damage before putting it into service.

Will be interested to hear other comments on this.

Hope this is of some interest.