Packard Forum Index » Post-War (1946-54)

Just realized that my '48 Packard is a positive grounded vehicle - i.e. red (+) battery wire goes to ground, not the black (-) wire.

So here is the question: Which wire is supplying all the power "hot" going to the dash, which ultimately supplies power to the Accessory Circuit Breaker?

Is it the wire that goes to the AMM Gauge (+) or (-)?

The wire that goes to the AMM (+) comes from the Voltage Regulator (B), which gets its power from the Generator and the Battery (+).

The wire that goes to the AMM (-) comes from the Starter, which gets it power from the Battery (-).

Thank you.

Pos was normally ground. Feed is: Battery Neg to starter solenoid and on same post is wire 1R which goes to ammeter (-). Out ammeter (+) 2RY to a splice point and also to (B) term on reg. If generator is putting out, then that current is passed back thru the ammeter to battery via that route. One wire off that same splice point 21A R2W goes to circuit breaker which is live all the time and from there feeding headlight switch, courtesy lights, clock, lighter, etc. Some items are protected with either the aux breaker or with additional breaker on headlight switch, some items not at all. Another wire from the splice, 21B R2W goes to ign switch AM terminal and then is switched. Most of car is fed from GA terminal off switch. Coil is independently fed off COIL terminal.

If you are using the 50 loom it is mostly the same in function and routing but there are some slight differences in designation, destination, and colors to be aware of. Also, it has been found by some that while Packard indicated schematically where a splice might be, in actual fact it could be somewhere else and was only drawn in a certain spot for convenience. You do have to follow a wire and find all the splice points.

Nothing on the car is polarity sensitive except that the coil is a little more efficient if properly oriented. Everything will work either way as long as generator is polarized to the orientation when hooked up. If ammeter reads backward, just reverse those 2 wires.

Won't hurt the radio to reverse polarity? I was always afraid of that.

On my 50, i left it pos ground, and when you're working with a volt meter, just remember that black is power (like in a house wiring). You can switch the leads on the voltmeter to make it easier.

Once you get working on the wiring (i have been the last few weeks) you don't even think twice about it. In fact, i was confused when i started working on a 12v neg ground project until i got oriented again!

Also, download and print off the wiring diagram here at the site in one of the service manuals....priceless when working, especially on the dash.

Also, if you need back there, 4 screws will let you pull the whole instrument cluster out some. Lay a towel on the steering column sheet metal trim to keep from scratching up either piece.

This is true. The only major differences between the '48 and the '50 is the dash and the tail lights. I am building a new '50 Harness to place into my '48. These will be my small challenges. It'll work.

Won't hurt the radio to reverse polarity? I was always afraid of that.

The standard Packard postwar vibrator type tube radio will usually work either polarity. Many cars have been "accidentally" changed over the years with no ill effects.

The vibrator, some noise filters, tube filaments or heaters, and the primary side of the main power transformer are all that see the "wrong" polarity and generally, those don't care. The secondary side of the transformer remains connected as it always was supplying the proper voltage and polarity to the radio. In effect the radio is running on a totally separate power supply.

Solid state radios are a different story and IF the vibrator in ours has been replaced with one of the modern solid state replacements, or radio otherwise modified in some way, then it may become an issue. If that replacement or mod is protected against reverse polarity with a blocking diode, no problem as it just won't turn on or blows a fuse but if not, then damage could occur.

I also wanted to add to your comment regarding splices. You are so right about this. Also, there was no Splice No. 4 and Splice No. 5... I found all wires going into just one splice which is totally OK. I guess this was to save the weight of one extra wire? HAHAHA

Thanks for all your help... so far. I'll have more questions later I'm sure.