1966 Valiant Engine wiring harness

[stinkyfromage]

I’m looking for a good/affordable engine wiring harness for my 1966 Plymouth Valiant. 225 Slant Six. It’s pretty brutal under the hood, wires all painted black and some sketchy connections. Somehow it all still works but I’d love to know it’s not going to burn my house down.

 

[Mattax]

AFAIK there is one manufacture that makes pretty good quality reproduction harnesses.
But they are not cheap. But if its just the engine harness, maybe its within your budget.
I don't know who, if anyone retails them in Canada. But for a sense of price go to Year One's website and look up a '66 Engine compartment harness. Year One has or had an exclusive on the many of the Chrysler engine harnesses from M&H. Probably 'cause they fronted some money.

HOWEVER. Your car needs a wiring hareness for a '66 Canadian Valiant. So if the price is in your ballpark, then contact M&H since I doubt Canadian version will be in YO's inventory.

Alternatively you can fix what you have. Its not cheap, but probably less than any harness made for you. The paint won't generally hurt the insulation. The colors for the engine compartment harness aren't that hard to figure out on a '66.

You'll need wire strippers, open barrel crimpers, some heat shrink and some Packard 58 and maybe some 56 terminals probably for 18, 16, 14, and 12 gage wire depending on which wires need repair.

I'd suggest also some harness tape and some cleaning materials too. You may or may not need more wire. Assess the situation first. From what I see in the photos there's mostly just bad terminal repairs. As long as there is enough length in the wires not to be stressed, and they can get properly supported, then the only other concern will be if the conductor is oxidized under the insulation.

 

[MadScientistMat]

This. If you want a ready made stock replacement harness, it's M&H or nothing. All the other kits (except for exotic race pieces) are just a pile of wires and connectors, lots of assembly required. Might as well order individual spools of wire from a place like Waytek.

 

[Mattax]

If you're near water, often a boat supply place will have marine quality wire in different colors and gages that can be bought by the foot.

The engine harness is pretty simple. I don't know the Canadian starter circuit that well, but if you post some more photos it will take about 10 minutes to figure out. Post them horizontal so they won't be shrunk as much.

 

[stinkyfromage]

Thanks guys, I guess that refurbing the existing wiring is probably the cheapest route. I was just looking for shortcuts lol. I got down this rabbit hole because the headlights aren’t working and while chasing that problem down I found a loose hot wire under the dash that arced out on the radio. It was a wire spliced into the cigarette lighter (I’m guessing it was supposed to go to the power roof switch). It got me worried
about the potential of “spontaneous combustion “ I guess. Anyway, until I get the wiring tidied up I’ll keep the battery terminals disconnected.

 

[Mattax]

Good plan.

Here's a little summary of the wiring concept. The car has two power sources, the alternator and the battery. They're connected together with the feeds to various circuits at a welded junction. So all of those wires are 'hot' when the battery is connected.

The headlight wires are typically bundled into the harness running along the driver side fender. They get power direct from the main splice and there is a circuit breaker inside the headlight switch. After that they are their own circuit. Th parking lights get power through a fuse.

The highbeam and lowbeam wire colors may be different but functionally its like this.

 

[Mattax]

Tips for removing the bulkhead connector engine side. question on the main harness plug on firewall

Discussions on cleaning here:
Cleaning bulkhead connectors
I like these but they only can get accessible surfaces.
I use both Deoxit 05 or stronger and CRC quick dry depending on the situation and what I have available. Also a little fibreglass electrical cleaning brush (looks like a mechnical pencil)

If the harness is real bad it can be worth taking the whole thing off and working on a benchtop a pice of plywood.

 

[stinkyfromage]

Good plan.

Here's a little summary of the wiring concept. The car has two power sources, the alternator and the battery. They're connected together with the feeds to various circuits at a welded junction. So all of those wires are 'hot' when the battery is connected.

View attachment 1716395777

The headlight wires are typically bundled into the harness running along the driver side fender. They get power direct from the main splice and there is a circuit breaker inside the headlight switch. After that they are their own circuit. Th parking lights get power through a fuse.

The highbeam and lowbeam wire colors may be different but functionally its like this.

View attachment 1716395780

Thanks so much for this. I’m pretty novice with the circuitry, however I tested voltage at the floor switch and I was seeing 4-5 volts. When I tested at the headlight I was seeing 0 volts. Is that symptomatic of a high beam/low beam switch?

 

[stinkyfromage]

Thanks so much for this. I’m pretty novice with the circuitry, however I tested voltage at the floor switch and I was seeing 4-5 volts. When I tested at the headlight I was seeing 0 volts. Is that symptomatic of a high beam/low beam switch?

This is while headlights were “ON”

 

[Mattax]

Thanks so much for this. I’m pretty novice with the circuitry, however I tested voltage at the floor switch and I was seeing 4-5 volts. When I tested at the headlight I was seeing 0 volts. Is that symptomatic of a high beam/low beam switch?

I would think that is multiple problem locations.
Assuming the battery is 12.5 volts with the light switch on (Check this), then with the connector to the headlight unplugged, the voltage should be very close to 12.5 V. If with both headlights unplugged there is no voltage, then there is a break in the circuit. It could be non-function dimmer switch or an actual break.

However with the lights not functioning, if the battery is 12 V, the power at the dimmer switch should have been 12 Volts.
Votlage only drops when current is flowing through resistance. So my next question is what did the ammeter show?
If current is flowing and its not going to the headlights, then there is a short of some sort.

 

[Mattax]

I just thought of something. With the headlights on, the tail lights are also on. (The front parking lights may also be on but most '66 models turned them off when the headlights turned.) So that may explain the 4 - 5 Volts.
The big IF is if the battery was fully charged and supplying power at roughly 12 Volts. But for now I'm assuming thats the situation.

 

[stinkyfromage]

I would think that is multiple problem locations.
Assuming the battery is 12.5 volts with the light switch on (Check this), then with the connector to the headlight unplugged, the voltage should be very close to 12.5 V. If with both headlights unplugged there is no voltage, then there is a break in the circuit. It could be non-function dimmer switch or an actual break.

However with the lights not functioning, if the battery is 12 V, the power at the dimmer switch should have been 12 Volts.
Votlage only drops when current is flowing through resistance. So my next question is what did the ammeter show?
If current is flowing and its not going to the headlights, then there is a short of some sort.

I would think that is multiple problem locations.
Assuming the battery is 12.5 volts with the light switch on (Check this), then with the connector to the headlight unplugged, the voltage should be very close to 12.5 V. If with both headlights unplugged there is no voltage, then there is a break in the circuit. It could be non-function dimmer switch or an actual break.

However with the lights not functioning, if the battery is 12 V, the power at the dimmer switch should have been 12 Volts.
Votlage only drops when current is flowing through resistance. So my next question is what did the ammeter show?
If current is flowing and it’s not going to the headlights, then there is a short of some sort.

I tested battery at 12 volts, didn’t check while light switch was on. I’ll check that out tomorrow and the ammeter. I really appreciate all the help. I’m new to this community but I have a feeling I’ll be spending a lot of time here lol.

 

[Mattax]

If the battery is around 12.5 to 12.8 Volts with nothing on, its usually pretty good.
Its likely then that there is a poor connection between the battery positive and the main splice.
Or, possibly poor ground connection.
The battery terminals don't look great in the photo, although its hard to see. So maybe thats a good starting point.

Arrows represent current flowing. Another way to think of current is electrons moving.
There's no current flowing to the headlights, so the drop in voltage isn't occuring in that circuit. It has to be occuring before the main splice.
Voltage only drops when the electrons have to squeeze through resistance.
Although its also possible the two grounding points used are not well connected.

 

[Mattax]

If the connector at the dimmer switch was backprobed, then there is a small current getting through to the lamps, but not strong enough to make the filaments glow. In which case it could be a poor connection at or inside the headlight switch.

With this scenario, measuring the voltage at the alternator's batt terminal will reveal the voltage at the main splice.

 

[Mattax]

Here's what I *think* we see.
I think most of the wire positions in the bulkhead connector are the same as shown in the US build service manual.

The biggest difference seems to be the routing of the battery feed and the start circuits.

One of the wires to the stud junction on the firewall comes from the battery.
The fusible link continues that circuit.
The other wire probably is the feed to the horn relay.

For the start circuit, the wire marked S1 gets power from the key switch in start.
With a manual transmission, there's probably no neutral safety switch. The circuit completes by grounding to the chassis.
With S1 energizing the solenoid, power goes through to the starter through the heavy cable direct from the battery and to the ignition through the replacement red wire.

 

[cudamark]

I don't see anything butchered, so, maybe just a cleanup is required. Overspray can sometimes be removed using just some lacquer thinner and a rag. I don't believe anyone makes those direct drive starter wires, so, you may have to custom make them yourself. Connections can be cleaned too. Sometimes contact cleaner will do it.....other times it needs a vinegar or lemon juice dunk or bead blasting. That's a lot cheaper than a new harness.