'51 Model 300 - Not sure where a wire goes....

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Navy Packard fan
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'51 Model 300 - Not sure where a wire goes....

Post by Navy Packard fan » Tue May 31, 2022 6:10 am

Great Americans,

In the process of getting my 1951 300 back on the road after an engine rebuild. I have one wire under the hood which must have broken free during the last several months of work. It's part of a three-wire group: two of the wires go to either side of the coil. I can't figure out from the shop manual where the third wire is supposed to connect. The car starts perfectly, so it's not part of the ignition system as far as I can tell.

Any ideas where this third wire connects?

Many thanks in advance....

Dave Czirr
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Re: '51 Model 300 - Not sure where a wire goes....

Post by Dave Czirr » Wed Jun 01, 2022 5:02 am

Does your car have standard shift with overdrive? If so, it may be a wire from the OD circuitry which instantaneously grounds the coil to initiate kickdown.

Navy Packard fan
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Re: '51 Model 300 - Not sure where a wire goes....

Post by Navy Packard fan » Thu Jun 02, 2022 9:19 am

Hi Dave,

Thanks as always for getting in touch with us here in the forums.

As for your question: No, mine has the Ultramatic Drive. I'm still Easter-egging around trying to eliminate what the wire does not go to.

As I look around at the brittle 70+ year old wires under the hood, this makes me want to order a new wiring harness and just begin replacing the original wiring, as I'm sure this will not be the last time this occurs. How tough a job is that? I am fairly good at electricity and electronics but I've never attempted that kind of job.

Thanks!

Howard56
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Re: '51 Model 300 - Not sure where a wire goes....

Post by Howard56 » Fri Jun 03, 2022 7:27 am

Can you get any sense of what color the extra wire might be -- if it is part of an original loom maybe peel back a bit of loom cover if the exposed portion is too faded. Other than the OD wire, about the only other original semi loose wires in that area would be for oil or temp senders but I believe those would be coming out from another section of the loom.

Jumping in on your other question, as one who has rewired a few cars, it is a somewhat tedious process but if you spend the money for a repro loom they usually come with very decent and in most cases step by step instructions. On those the wires are labeled and it is mostly a matter of remove one wire and replace it with new following some kind of chart. In all probability some sockets may be Packard only and you will need to remove those from the old loom and reattach to the new loom. I think it is much easier if the dash or at least the cluster is removed but that in itself can be problematic. Engine compartments are not much of an issue and many have successfully done dash work by laying on their back to work under the dash. In some cases seats were removed for a more comfortable laying experience but others have managed to contort themselves and hang their legs over the seat back with the seat still in place. The laying on back work all comes down to how flexible you are and how much pain and stiffness you can endure. Getting and keeping a decent amount of light in the right spot can be fun.

Several have also bought the so called modern universal loom kits at a much lower cost than repros from some of the steet rod and wiring places. Using one of those kits is a bit more involved because in most cases the wire colors they use are GM or Ford spec which are not an exact match to Packard. On those you are kind of on your own to interpret the colors the loom maker has used in a circuit to what Packard has on the wire diagram. Again, it is step by step -- remove one wire and attach another. If you do go universal and are still running 6v be sure and try to get a loom labeled as heavy duty. Some of the vendors offer them and the difference is the wire size is larger which can be important with some 6v circuits.

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Re: '51 Model 300 - Not sure where a wire goes....

Post by Navy Packard fan » Fri Jun 17, 2022 10:55 am

Howard,

Thank you for the information on the wiring harnesses. My wires are all original and I think they ought to be replaced just for safety.

As for my muster wire….There are three wires in this loom: one goes to the negative side of the coil. A second wire goes to the oil pressure sending unit. The third wire is a mystery. When I attach a test light, the wire is hot (the test light comes on), even when the ignition is off.

Thanks!

Howard56
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Re: '51 Model 300 - Not sure where a wire goes....

Post by Howard56 » Fri Jun 17, 2022 11:44 am

Is the wire going between the positive side of the coil and the distributor terminal a short loose wire or is it part of the loom?

The temp sender is at the rear side of the head just above the starter motor. Is it hooked up and does the gauge work? That wire usually comes out of the loom portion going to the starter but even though it would be a long stretch, is the only other factory item with a loose wire I can think of on that side of the engine. Temp ga wire should not be powered unless the key is on so doubt that would be it.

As I recall, the generator has three wires in another portion of loom coming from the left fender area and starter switch on carb comes from the firewall near heater box -- two wires to switch with a third wire maybe going over to the heater blower motor. As the mystery wire is on all the time any chance it could be an aftermarket wire and someone just held it with tape over the original loom?

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Re: '51 Model 300 - Not sure where a wire goes....

Post by Navy Packard fan » Fri Jun 17, 2022 1:27 pm

The positive side of the coil has a short wire that goes to the distributor it is in place and seems to be working normally. You’re correct about the starter switch and the heater blower motor they come out of a different portion of the firewall and go on the right side of the Engine compartment.The oil pressure sensing light works when the ignition is turned to the star position and then goes out, so I know the pressure sensor is working. The temperature Sensor, which you correctly identified is coming out of the rear part of the firewall near the starter motor, is also hooked up and working, I have a good indication on my gauge.

The loom is completely original and undisturbed. It doesn’t look like anybody has ever touched any of the wiring underneath the hood.I’m not keen to start pulling it apart, because I’m afraid I’m going to break the wires, or at least, damage the insulation and caused myself a short.

I’ve been scrounging through the service manual, but I haven’t been able to figure this one out. The electrical section doesn’t reallyHave a good photograph to go off of, and the wiring diagram is obviously a schematic so it does not capture where the wires fall within the engine compartment.

Howard56
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Re: '51 Model 300 - Not sure where a wire goes....

Post by Howard56 » Sat Jun 18, 2022 7:23 am

It is a puzzlement. Without knowing the color of the extra wire it is kind of hard to guess what is going on and the fact it is hot all the time is also odd. Granted, there is constant power to a couple of places in the engine compt but other than power to the horn relay which is always active, there is nothing else stock in the engine compartment that is not switched on somehow. Certainly nothing close to the coil. I am wondering if the poor condition of the wiring has allowed the wire to lose a chunk of insulation somewhere and touch something that is hot.

In that section of loom you have power to the coil which would be a yellow wire direct from the COIL terminal on the ignition switch. Another short wire -- often black -- goes down to the distributor, a brown with white tracer wire to the oil sender, and the only other wire that could normally go thru the loom ending in the coil area would be a green with black tracer wire for the ign cutout if the car was equipped with overdrive. That wire would go to a point on the lower firewall above the accelerator pedal where the kickdown switch would have been mounted to the accelerator linkage bracket. It would not have power because the kickdown cutout circuit briefly grounds the wire which would connect to same coil terminal going to the distributor.

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