The Stovebolt Site Forums The Shop Area The Electrical Bay Electrical System on my 50 1 ton

Hey there!!! I've not posted much, but I really enjoy reading everyones posts! Now I need some help!!
Last April I bought a 1950 GMC 1 ton at an auction! Me and a friend got it running with a 12 volt battery. At the time, I was going to change it over, but now I've decided to keep it six volt. It turned over, then began to fire....ran to the point I could drive it around. I did a few times. One day, I tried to start it and nothing! It hasn't ran since. It would turn over, but never fired.

I took the distributor cap off and found the spring on the points was burnt in to. I replaced the points, and they got hot. At the time, the 12 volt was in place. I was told to put a six volt in and I quickly robbed the one from my original 54. When we hooked it up, and began to turn it over, the points began to smoke. Two more sets of points and we decided to change the condenser. (Already tried switching the coil). Although I haven't tried to work on it the last week with the Holidays on us, I am anxious! I was reading some other posts...and I came across the positive ground issue!!! So....question is: Is my truck positive ground??? The red wire goes to the ground, but I've been hooking that to the negative post! If I hook the positive to the red ground wire, and the negative to the starter do you think it will help my problem? Do you think the condenser may be shorted and causing it? I've never seen points burn the way these have....the contacts still look new! Thanks guys...and girls.....I'll have my girlfriend take some pics soon to post!!!!

CaptainMo,

I'm not a GMC guru, but it sure sounds like you had it hooked up backwards.

I'm pretty sure the standard polarity connection for a GMC your year was POSITIVE ground. Although battery cables can get swapped all over the place by unknowing folks, the battery has a large post which is POSITIVE, and this would make sense to be connected to a red cable, which should go to ground.

Your problem sounds like too much voltage for the ignition system, but this could be exacerbated by wiring it backwards.

The wire from key to coil would attach to the -, or negative side of the coil if the rig were wired for POSITIVE ground.

The ammeter would show a constant discharge if the thing was wired backwards too.

I would try the six volt battery, with big, adequate cables and make sure to attach it NEGATIVE post to starter and POSITIVE post to frame/engine/ground.

A new set of points and condenser would probably get you going again. The coil is probably OK, but headlights and other little lamps and gauges don't really dig all that voltage.

Again, I am not sure on this, but I think it's right...good luck.

Stuart

Thanks Stuart!!! I'll try all of that!!!! I really appreciate the help....my dad was a very good mechanic on this older stuff...but he's gone now......Now is when I miss him the most!

Although I haven't tried anything yet, I'm still wondering if there are any other ideas?!!? Let me know!!! lol...Thanks....the Captain!

Reversed polarity should not make your points overheat. Leaving the ignition on with the motor not running can do it. The one possibility, assuming your battery is truly 6 volt is that the coil has developed a short inside. The damage could have occurred when the 12 v was hooked up.

If this is a US truck, then the original setup would have been positive ground. Canadian GMCs used Chev chassis and they were negative ground.

Trucker....I checked the coil...it seems to be ok....in fact...I pulled one off my 54 delray.....and it still smoked the points!

Do you have the wire from the ign. switch going to one term. on the coil & the other term. on the coil going to the points term on the dist.? What about a radio suppressor? If it has one disconnected. If that is correct I can't see any way it can smoke the points like that.

yes....the ignition is hooked up correct. There is no radio suppressor. This truck was running fine on the 12 volt battery, even though it was a 6 volt system. If the condenser shorted out, could that cause the points to burn? I'm thinking, new points, new condenser, positive ground...and keep my fingers crossed!!!

CaptainMo,

Part of my confusion on this post is the statement you made indicating that it isn't the point surfaces proper that are being affected, but the spring or arm that burnt in two.

The point contact surfaces are where the current flow is broken and is made...this is the surface that erodes. The condenser is there to quench the arc at this "switch" and to aid in collapse of the coil primary.

Are your points cooking on the contact surfaces or somewhere else?

Stuart

If you have a test ammeter put it from the dist term to ground with the points open. It should be no more then 2-2 1/2 amps. I agree if you replace the points & cond. it will work. Do not use 12 volts without a resister & do not leave the ign. on without it running for more then a few seconds. The latest issue of Vintage Trucks has an extensive article on dists. & points.

Wrenchbender....The contacts on the points are in new condition......I haven't left the switch on at all.....And even if I did, I always disconnect the battery due to a drain. Anyway...it is the spring part that is burning in to! I have NEVER seen this before!

Thought >....... All ing. systems run on four to six volts. If you change your coil and I'am not sure you did ?? did you get the right replacement coil. Some coils have a resister in them and some need an external resister. Even twelve volt systems need a resister of some kind or at least should. Also maybe the wire to your ing. contact points may be shorting out where the wire enters the distrubitor. Check the insalator where the wire passes through. The postitive / ground hook-up is not the reason for the short in your system. As far as I ever knew all six volt systems were pos. to the ground.

Let us know what you find wrong .......

I,ve done hundreds of these & have never seen anything like that. Some premium points have a copper strip that goes along with the spring. The regular production uses the spring as the conductor.