P1800 ignition wiring questions

Since I'm trying to avoid frying the wiring harness, a post to ask for guidance seems wise.

1962 Volvo P1800, there's a thread in showroom. Almost ready to start and drive this thing, after many months of restoration.

Car came to me with no key and an aftermarket ignition coil. I don't have a spare armored cable one and I'm not forking out $800 for a reconditioned one so I want to use what I have.

Wiring diagram shows this:
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And this:
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And also this:
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Wires are correct in car, and in good condition with some minor changes. The current ignition switch is a VW one, also labeled 30, 50 and 54. I don't have a key for it.

I have this additional wire running from post 54 on my ignition switch to the positive side of the ignition coil.

Now, my issue:
What goes where when using an aftermarket ignition switch:
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I'm drawing a blank when trying to translate the Volvo/VW codes on the ignition switch to this 'Murican switch bought at a local speed shop. In short: what goes where ?

Side note to those familiar with the early P1800's. I have the external unit for the rev counter, the small (expensive) box mounted behind the grill. Diagram shows white, black and white/black running to it. Since the unit wasn't on the car, I don't know where the wires go. Any idea ? Green books do not show any information.

I would suggest using an ohm meter to verify switch operation. From what I can read on the aftermarket switch. These are only my guesses because I would ohm out the switch to verify.

American cars and newer volvos have that acc position which turns on a few things but not the ignition. It would turn on stuff like the heater and wipers for example. So I would guess that 54 would go there.
Ignition should turn on the ignition system and stay powered under cranking. So I would guess terminal 15 on the coil would go there.
The large center terminal would be the one to crank the engine or apply the terminal 30 power. Then the bat terminal would either crank the starter or be where terminal 30 goes with the bat terminal cranking the engine.

As I wrote though. A few minutes checking with a ohmmeter while verifying what connects to what in each key positions will tell you.

30 = BAT (brown wire)
54 = ACC (white wires)
50 = ST (white/red wire)
Coil+ = IGN

Here's a pic of the tach sender wires.

Thanks guys, I will hook up the rev counter and double check the terminals. Looks like I'll be able to start the car today and then have it back to stock configuration with some parts from Hi-Performance Auto. **happy dance**

if you have a ballast resistor before the coil, some cars will send a bypasses straight 12V+ to the coil from the starter for a "hotter" spark during cranking. maybe that is your extra wire?

apachechef said:

if you have a ballast resistor before the coil, some cars will send a bypasses straight 12V+ to the coil from the starter for a "hotter" spark during cranking. maybe that is your extra wire?

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It may have been removed but this car doesn't appear to have had a ballast resistor. I ran out of time to work on it this morning, I'll try to carve out some time tonight but it will be Tuesday before it starts. I want the friend who's been working on it with me to be here when it starts for the first time and we're both gone until then.

Up and running as of last week. Tach isn't working, I haven't taken the time to check if it's corroded wire connections, a bad rev counter or a bad tach. Bad rev counter or bad tach would be costly, hopefully it's something simple.

Always satisfying to hear that project car come to life. Glad it’s moving right along.

thismachine13 said:

Always satisfying to hear that project car come to life. Glad it?s moving right along.

Click to expand...

Thanks, definitely satisfying.

Still troubleshooting some gremlins. Headlights don't seem to be getting any power at the fuse, so I'll try another headlight switch and see what gives.

More troubling is the fact that the car ran for 45 mins last week on the wiring mentioned above. Then it stalled out 2 days ago and lost spark when we tried to re-start it. No spark from the coil, no power to the coil from the ignition switch. Tried another (new) switch, same thing.

Puzzling to say the least.

More head scratchers: red wire from ignition switch to positive side of coil is getting power. From the switch, the power pulses when I try to crank the car.

Ran a solid wire from the + terminal of the battery to the + side of the coil, no dice. Still no power out of the coil going to the distributor cap . Same issue with the two other coils I tried.

matt b said:

Ran a solid wire from the + terminal of the battery to the + side of the coil, no dice. Still no power out of the coil going to the distributor cap . Same issue with the two other coils I tried.

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That is a slightly confusing statement. Are you applying a constant +12v to the + terminal on the coil and expecting to be able to measure a voltage on the center high voltage terminal of the coil without the car running?? If so, you won't measure anything if the ignition points are closed so not a very good test of anything. If you meant that with a +12v supply to the + terminal (effectively 'hot wired') and you crank the engine you don't get any spark, that is different. If the latter, it means one or more of the following:

1 - the coil has failed,
2 - the connection between the coil - terminal and the distributor is broken
3 - there is a permanent ground somewhere on the blk/wht wire between the coil and the distributor - a problem with the tach sense circuit?
4 - there is a problem with the ignition points or the condenser including a permanent short to ground on the points / condensor

To test the coil, use an ohmmeter to measure the resistance between the coil + terminal and the coil - terminal. Typical resistance values could be in the 2 ohm range. Measure the resistance between the center terminal of the coil and the coil - terminal. It should be high, maybe 1000 ohms or more. If either measures infinity the coil has failed. Non infinity values don't guarantee a good coil; but, infinite values do guarantee a failed coil.

Since you have tested with two other coils, I would be inclined to start with #2, #3 or #4. Do a static ignition timing check and that will confirm that your points are at least opening and closing.

Curious about your coil arrangement. Since you replaced your ignition switch I presume you no longer have the original armoured supply wire to the ignition coil which is how you are accessing the + terminal on the coil?

matt b said:

Thanks, definitely satisfying.

Still troubleshooting some gremlins. Headlights don't seem to be getting any power at the fuse, so I'll try another headlight switch and see what gives.

Puzzling to say the least.

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I don’t think the early cars had a fuse for the headlights. IIRC it’s full power, unfused through the headlight switch then to the headlights. Headlights could be turned on with the car off. If you’re using an aftermarket headlight switch it may or may not be able to handle the load.

What fuse are you referring to?

Some info here, lots off reading material too.

http://www.sw-em.com/lighting.htm#relay_controlled_headlights

Disconnect the tach wire from the distributor. It may be killing the points signal.

Also, check that the small bolt for the points/condenser isn't touching the distributor body.

Thanks all. I think we have an issue with the small bolt on the distributor grounding out. If that's the case, it would explain all of our symptoms and how they came on suddenly.

I'll get rid of the tach wire for now, the tach isn't functioning anyway and keeping it in the loop just adds an unneeded variable.

c1800 said:

I don?t think the early cars had a fuse for the headlights. IIRC it?s full power, unfused through the headlight switch then to the headlights. Headlights could be turned on with the car off. If you?re using an aftermarket headlight switch it may or may not be able to handle the load.

What fuse are you referring to?

Some info here, lots off reading material too.

http://www.sw-em.com/lighting.htm#relay_controlled_headlights

Click to expand...

Forgot to respond earlier.

It's a bad headlight switch. I tried two, and both are bad. I bypassed the switch to isolate and confirm that the headlight relay works and that all wires were getting proper juice: everything checked out just fine. If we plug our wires back into the headlight switch then we get no headlights (wire to headlights receives no power from switch) and dashlight stay on all the time, even with the ignition turned off (wire is always hot). I'll grab another 5 prong pull switch from Moss Motors or a similar place. There is a fuse, it's the forward most fuse box on the panel located in the engine bay.

Repaired the tired distributor as best as I could, using parts stolen from other distributors. Screw was grounding, but now I need to track down a condenser and points to bring fresh life to this distributor. Spark is currently very weak, too weak to even start the car.