PT81PlymouthPickup

Would look even better with blackwalls! ?

Nah! There should be a law prohibiting whitewalls on trucks! Just ain't right! Lols! ?

Just my opinionated opinion, but whitewalls look better on cars. I prefer black walls on trucks. Plus, I can't imagine painting a tire would hold up very well?

I guess there's many ways to look at it. I look at it like therapy. Put-zing around fixing and improving my truck takes my mind off the darker realities of life. The driving part can be a bit intimidating when competing with modern vehicles on the roadways. On the other hand, it is exciting not knowing if you'll come back home alive. Well, more likely under your trucks own power. Lols! Good idea to have some towing coverage. Even with some of the changes I've made; (front disc, Borg Warner T5, higher ratio differential, seat belts) I still opt for the rural routes whenever possible. I'm the first to admit! My truck is still a death trap in a bad accident. But I guess I'll keep driving her. Might be luckier to die behind the wheel then at a Nursing home? It's later than we think. Cheers! Ha!

Oh yeah! Probably a good idea to disconnect your battery. Un-fused feed wire to ammeter could possibly cause catastrophic event if you ground it by wrench?

I'm 66 and just finished doing a bunch of stuff under my 39 truck dash. I learned quickly to take a couple aspirin before starting each session under there. Lols! If you lay on your back with legs hanging out drivers side it's doable. It took some patience to not get frustrated. The trick for me was getting good light under there and then work methodically with 1/4 inch drive ratchet set being careful not to disturb wiring to much. If I remember correctly, after unscrewing the speedometer cable, and pulling out the dash light, there's only a couple nuts requiring a 3/8 socket to remove the assembly. Other option is get some young guy to do it for you. Good luck with that!

My 1939 has a fused third terminal on the ammeter which was hooked up only to the light switch and horn. The fused terminal does not go through the gauge. On my truck as originally wired, the only thing registering on the meter was the charging circuit. I'm confused why they did it that way? Turning on lights or using horn does not show any draw. Not certain, but I think 39 might have been the last year for that? I believe in 1940 the light switch was wired from the ammeter and there was a fuse on the light switch.

During re-examining all things electrical on my truck, (12v neg. ground converted) I was pondering if my neg ground cable should be where I affixed it many years ago? I used one of the bolts in the top of the T5 transmission. The original cast iron 3 speed had the ground anchored there. Haven't had any issues, but not sure that's the best place with the more modern gear box? I'm thinking it may be better to anchor to a bell housing to block bolt? Anyone have experience with this?

Does your ammeter have a fuse in the back of it?

I have wired my 1939 PT81's amp meter as per Mopar wiring diagram. The light switch and the horn are wired to the third terminal on the ammeter which is fused. Everything is working fine, but neither the lights or the horn show any indication of draw on the amp gauge when I use them. Does this sound correct? I know the ammeter is working properly because other accessories such as heater motor indicate a draw. I'm guessing that Mopar originally used the ammeter for just the charging circuit?

Flatheads forever!!! ?

Getting ready to install my new starter switch. Anyone know if the contacts should be lubricated or left dry? When I took the switch off there was a black grease that had definitely been applied to the copper contact surfaces. I rebuilt this starter 35 years ago, but can't remember why I lubricated it or if it was even supposed to be? My dad, a professional mechanic was alive then. I'm thinking he may have suggested lubrication? I'm wondering if it may have been some special lube? I was thinking of applying a light coat of anti-seize? Thoughts and opinions welcomed!

Lols! I certainly don't need any more maintenance opportunities! My old buddies mom used to say: "You'll become a slave to your possessions" We didn't know what she was talking about back then, but I sure do now. Yeah! You would think those lower contacts would be easy to source? Common wear item back in the day. Somebody must be hoarding those somewhere?

After more searching, turns out it is for a trigger wire for a Sisson choke. Not much room or a provision in there for the connection. Would be interesting to see the connector they originally used. Evidently they must have used the electric chokes on some vehicles with foot starters.

Like a dummy, I over tightened my battery cable connection to my starter and damaged the copper threads on a like new starter switch. ? I can't figure a way to repair it, so I ordered another one. $50 mistake Lols! Anyhow, I noticed it has a hole in the side with a brass grommet which is electrically insulated? Anyone know why that is there? I'm also trying to locate a lower contact (#687377) which is attached to the starter body. Can't seem to find one anywhere. It has a pretty big eroded area where the contacts meet. I'm thinking I could remove it and fill it with silver solder, but not sure that would be OK? Perhaps fabricating a new one might be better? Ridicule and advice welcomed!

Jerry, what manual did you get this TC, TD diagram from? I have a shop manual for the R series trucks which looks pretty much the same as your diagrams. I've never been able to find a specific shop manual for the 1939 Plymouth PT81s. I think it would be the same as the 1939 Dodge TC?

Yeah! The damn things fly off when you don't want them to, and difficult to get off when you do. I tweaked my clips and they stay on fine now, but it's a struggle to get them off without damaging the paint. If the clips are in just the right positions they do work fine. Only takes one lunkhead to damage the clips if the cap is not taken off carefully. You can still find new clips, but they're riveted on. It's a project to replace them correctly.

Thanks Jerry! This is helpful, but a little difficult to follow the circuits. I'm pretty sure the harness I have is not exactly right for my year.

Anyone have, or might know where to get a wiring diagram specifically for the 1939 pickup trucks?

After examining more closely, I think I may have a solution? In my diagram below the amp gauge on the left is how I had wired it years ago I believe incorrectly. The one on the right is how I think it should be wired according to the Mopar wiring diagram. But, it originally had just a cut-out relay on the generator. So, if I hook it up like the gauge on the right I will be running the newer charging system thru the fused circuit. My harness has the generator wire, horn, and headlamp switch all on one connector. I could change just the alternator wire from the fused terminal and connect it to a non fused one. Just not sure best way to go? I can't imagine it would be smart to leave it this way. If a short occurred in the lighting circuit then the alternator would not charge. Advice welcomed!

Hi Dan, Thanks for your response and offer! But no need to diagram your circuits. From my recent quasi research the 39 PT81s originally should have a 30amp lighting fuse on the back of the amp gauge and a high beam indicator in the switch knob. Strange that yours is different? The stem of the light switch is hollow, allowing illumination from the bulb to project to a jewel in the knob. My switch has the bulb, but I don't have the jeweled knob. In fact, I've never seen one. Only one of three terminals on the amp gauge is fused. I just discovered I had powered my light switch from a not-fused terminal. A mistake I made many years ago. I've been driving it trouble free for many years with totally unfused lights, and horn. (Fire waiting to happen?) I did at a later date add a radio, heater, and signal lights which I did install individual fusing for each of those. So, my current thinking is to switch the lead powering my light switch to the fused terminal on the amp gauge, and add a inline fuse for the horn. Like you, I also switched out my generator for an alternator. I installed a 1970's era Mopar charging system with an electronic regulator. I did however switch to 12v negative ground system. It too has worked perfectly for many years, but I'm thinking now that I should add a fusible link to protect this circuit? Does that make sense? And as for the headlamps, also like you, I installed halogen light bulbs. I have no idea about current load, but they have been working fine without any relays. I'm currently trying to figure out how the high / low beam switch works. Since the headlamps are only one filament bulbs, I'm guessing there must be some sort of resistor in the dimmer switch to reduce the full current to the lamps for low beam? I installed a Pertronix module in my truck a couple years ago. It works well, but if you want to do it right, the install was not quite as easy as they would have you believe. I ended up pulling the distributor and modifying the housing by adding a hole and grommet to get the wire through in a better spot for proper strain relief.

Thanks Merle! Very helpful. I suspect my earlier switch has the same designations. Perhaps A meant auxiliary?

Does anyone know what the letters D, H, B, A, R, stand for on this headlight switch? Original switch, out of my 39 Plymouth PT81 truck. I figure B is for battery, but not sure about the rest?

I am totally confused. Senility is creeping in. I wired this truck about 25 years ago. I can't remember much about it now. Anyhow, after checking some parts books, the switch listed for the 1939 PT81 was 591181 which is the one I have installed. It does not have a fuse. I just read in another Mopar manual that the a fuse on the back of the amp gauge protects the lighting circuits? I'm going to pull that one tonight and see what stops working. I'm guessing if a short occurs anywhere in the lighting circuit, all the lights will fail? Would be preferable to have stoplights and signals on separate circuit? If the fuse at the ammeter does in fact protect the lighting circuits, at minimum I can easily add a fuse for the horn and possibly a fusible link for the charging circuit. I'm wondering if the fuse at the ammeter also protects the charging system? I consider myself fair at mechanic endeavors, but this electrical stuff hurts my head! I'm on a mission to figure this out! This quest all started by me wanting to document and list the location of, and amp ratings of fuses. When I kick the bucket, at least my son or the next owner might have a clue? Lols!

Yes, I think my used switch may or may not have been original to my truck, but it certainly looks like it would be the easiest way to protect the headlight wiring. I too thought about taking the switch apart, but it's very corroded. All of the original plating is gone and rusted. If I can find an NOS one would be preferable. I'm not sure how to identify the applications for this switch and corresponding part number? The aftermarket one I found looks right, but I'm always suspect about aftermarket stuff quality.