Ford CMP Voltage Regulators

BCA · #1 22-07-12, 21:59

The wiring schematic in MB-F1 shows the battery as having a positive ground. Various Ford parts books show a choice of a voltage regulators with either positive ground (regulator C11A-1505) or a negative ground (regulator C11AS-1505).
I can't see any discussion in the manuals about the regulators being either positive or negative ground. Why were there these variations.
If your ammeter reads backwards then it would indicate you have chosen the wrong battery terminal as your ground.
Can anyone clarify this issue.
.... Brian

Tony Smith · #2 23-07-12, 14:47

Brian, you need to re-check your parts stock! The basic Ford number for voltage regulators is 10505, not 1505.

These were a common part across many Ford vehicles, and not simply restricted to CMPs or even military vehicles. In the CMP parts lists, there are an amazing 9 variations of these regulators listed, with differences being for:
1. Pos or Neg earth,
2. Battery Specific Gravity (a new concept to me, I thought all batteries ran the same spec grav for "charged" or "discharged" state!), and
3. Country of manufacture.

I have in my possesion a "Made in USA" reg, a "Made in Canada" and an ENFO "Made in England". Only the English one appears slightly different (and that may be because it is possibly Post-War manufacture), yet the mount holes are identically spaced and will interchange with the North American versions. It is not listed in the CMP Spare Parts Lists, but I also have references to a 35amp regulator and a 50amp version.

Why the option of Pos or Neg earth? As stated above, these were a common item across many Ford models, for export to many countries. Even the "Standardised" CMPs were specified differently for particular contracts to certain buyers. I would presume the contracts for supply to Britain and possibly India would have followed national preference/practice at that time for Pos Earth vehicles for compatibility with existing fleets, while contracts for supply to Canada would have followed North American preference/practice for Neg Earth. On Australian Blitzes, I have seen both Pos and Neg earth systems, so our stock of CMPs would have come through a variety of supply contracts.

cletrac (RIP) · #3 23-07-12, 15:12

Pretty near all Canadian 6 volt systems are positive ground and 12 volt systems are negative ground. There are exceptions of course but not many.

Phil Waterman · #4 23-07-12, 17:33

Hi All

Is the Positive 6 volt Ground a Ford thing?

All the Chevy trucks of the prewar and war years that had 6 volt systems with Negative Ground, I've encountered . My copy of 1940 Shop Manual for Passenger Cars and Trucks for General Motor of Canada shows on the wiring diagram Negative Ground for both on the car wiring diagram and truck wiring diagram.

Checking my MB-C1 and MB-C2 both show Negative Ground

What have other people found?

Cheers Phil

Grant Bowker · #5 23-07-12, 19:16

Most (all?) GMC trucks of that era were positive ground, with Chevrolet being negative. I have no idea why General Motors did their two truck brands differently.

Mike K · #6 24-07-12, 03:03

I believe the early Dodge 1/2 ton WC series were positive ground 6 Volt . Gordon will know more .

There were NOS Ford regulators around . I had one .You have to clean the contacts before use , they tend to oxidise . Mike