67 P220 eletrical issue

gjr0 · Post by **gjr0** » 24 Jul 2023, 15:51

'67 P220, mostly standard (bored to 2.0L, mild cam, etc) with a Delco 10Si alternator. Yesterday I noticed that shifting into reverse caused the AMP light to come on. Before I left for work, the wipers and turn signals worked. As I drove to work stepping on the brakes, turning on the wipers, the fan, using the turn signals, turn on the overdrive, headlights all caused the AMP light to light up. None of the above systems actually functioned. When I turn the ignition on, the AMP light does not light up.

The battery cables, wires to the alternator are tight. The in car voltmeter reads a shade under 14 V. An external voltmeter reads 12.66V with the car off, 14.2 at idle. It also measured 32 VAC at the battery (two different meters).

Would a dead rectifier in the alternator cause those symptoms ? If not...
Thanks
Greg

Post by **scot850** » 24 Jul 2023, 23:10

Check your grounds are all good, especially the main one to from the exhaust to the body (if I remember correctly). I'm not well versed in electrics, but it sounds like a ground issue, but could be a bad voltage regulator, but you say everything is reading correctly. Seems when you add a larger load is when you get an issue. What does your charge system show in terms of Voltage when you switch on a large load like full beam lights and fan motor?

Neil.

gjr0 · Post by **gjr0** » 25 Jul 2023, 18:15

The grounds all check out, bolted up tight and 0 ohms between the negative battery post and the body, the alternator and the engine.

While I was checking the effect of turning on the various systems I was probing the connectors on the fuse box. The good news is that the symptoms disappeared. The bad news is I don't know why. I pulled all the connectors off the fuse box, gave the loose ones a little squeeze, cleaned up the spade terminals and fuses. The symptoms made on brief reappearance but mostly it is good.

It is hard to tell but rivets between the spade terminals and the fuse contacts might be corroded or slightly loose. It looks like a couple of the spade terminals move but the copper fuse contact does not.

Coming back to your question, turning on the headlights, the blower, the turn signals and the wipers pulls the system voltage down to 12.3V at idle. Revving the motor up to 2000 rpm brings the voltage up to 13.8V. One odd thing - measuring the AC ripple at the battery with the + probe on the positive post and the - probe on the negative post gives 30VAC. Reversing the probes give zero VAC ( or nearly so).

Post by **scot850** » 25 Jul 2023, 23:41

The fuse box for what it is and even the fuses can give you grief. Corrosion on the ends of the bullet tipped ceramic fuses was a common issue even 45 years ago when I was running my first 2 120 series Volvos. I even found issues with the spade connectors to the fuse box and even the fuses themselves looking ok but being dud.

Glad you have found a somewhat unknown solution for now.

Like I said the electrics are not my strength, but as you are running an alternator it sounds like a reasonable charging rate, but maybe a little low under load. I don't know the significance of the 30 VAC other then knowing the system is a 12 VDC system, and the alternator and regulator convert AC to DC for the electrical system. As there is a diode in the alternator, that may explain why you only get the reading on one direction. But I am out of my depth!

Neil.

gjr0 · Post by **gjr0** » 26 Jul 2023, 04:34

Out of your depth ? The idea to check the grounds (and supply) pointed the right direction.

These cars fall into the electrical rather than electronic realm, my favorites. A slightly corroded or loose rivet is an easy fix. No car made today will be running is 50 years due to electronic failures.

Thanks for your help.
Greg

Post by **scot850** » 26 Jul 2023, 19:14

Glad to help. Loved my 122S, and 123GT, unfortunately never completed my 222S before moving to Canada. Bodywork and paint was done. Sold to a friend who wanted to finish it.

Neil.

gjr0 · Post by **gjr0** » 26 Jul 2023, 19:51

They are great little cars. Straight forward and well built. And fun to drive.

Follow up #1
I removed the fuse box, cleaned the loose contacts and rerivetted the connections between the spade terminals and the fuse holders.

To do that, hold a 1/4" punch vertically in a vise. put the head of the rivet on the punch and use a 3/16" punch to tighten the peined side of the rivets. The punches are lined up when the fuse box is held securely and it is level. Give the 3/16" punch a tap and see if the terminal has any perceptible movement. If it does, give it another tap. keep trying and tapping until you can tell that it is not moving. You have to be a little careful hammering on the 50 year old plastic.

Checking the resistance of the fuse box (with the fuses installed) showed a fraction of an ohm. Now that I am pretty sure the fuse box won't catch on fire, I'll drive it for a while and see if the symptoms came back. .
Greg

Post by **scot850** » 27 Jul 2023, 15:08

Fingers crossed!

Neil.

122sPhil · Post by **122sPhil** » 24 Oct 2025, 14:28

I stuck a Gm alternator in my 122 20 years ago.
when I drive I see the red alternator ( well I guess it would be generator) light coming on.
if I turn the headlights on the generator light goes out.

like yours, mine did charge the battery fine so I ignored it for the past 20 years but it is on my bucket list

on my last little run the alternator bearings started squealing..

wondering if I should go back to alternator or put the OEM generator in. the second 122 . I just bought is all original despite being a bit rough looking, even the plastic bag washer reservoir is original. I think I'll keep that one as a generator.

cleaning grounds wont hurt and maybe its a good thing to do at least once every 30 years..

I think something was always goofy wiht my alternator's internal voltage regulator, but I never did prove the issue. the engine revs pretty high so I wondered also if I am over reving the alternator, I have no idea if the pulley is right of if it is actually possible that i am over reving it. pully size may affect alternator's rotational speed.

I think the fuesebox is actually balkalite, so its not going to crumble to dust like plastic, but it may be fragile, so Id be careful with the riveting.

occasionally I'll take stuff apart that was put together with rivets. the electronic store sells small screws, in 1.2 3 4mm sizes , they seem to be brass with a plating , not iron. so good for electrical contacts.
With small secrws and nuts , you dont need to pound on stuff.. it might be an option.

Post by **volvolugnut** » 25 Oct 2025, 07:58

122sPhil, Thanks for all of your comments on older Volvos. There are fewer and fewer knowledgeable people on the oldies and you have many practical suggestions.
volvolugnut