Generator resistor? heat sink? current draw on Enf707

[Gmerrill0516]

The 1949 LS85 I'm working on was retrofitted with an alternator some time in her service life. Now that I am working one problem at a time to starting it, I have come up with a 60+ amp current draw. The 6x6x6 finned cube (resistor/heat sink?) was quite hot and made a little puff of white smoke so I shut the power off. To confirm the issue, I disconnected the five or six wires from it and sure enough the draw issue stopped when I flipped either ignition on. The test light says there is one hot wire going to this unit when the ignition(s) either one or both are turned on. (Dual ignition obviously). I'd like to know for sure if this is a problem and what I need to do to solve it. Is this thing shorted out? Is there a test to prove it out? Does anybody sell new or rebuild them?

The book says to look for bad points or a bad coil but I determined that these are normal and still powered despite disconnecting the finned unit and the high current draw is not there at this point. She cranks over great now that I have adequate batteries. The starter is overhauled and has fresh brushes. It is a 12V system and I've hooked it up negative ground. The wiring is not great but is not shorted. The hot spot is clearly this item. See pic.

All help and guidance is appreciated.

Greg

[609albert]

looks like you have a rectifier (most fire trucks had them) to balance load from Lights,siren etc. I know they sometimes burn out, try Ebay for a replacement or a starter /generator shop in your area. hope that helps

[Gmerrill0516]

It does as at least I know what to call it. I'll search on that and see what turns up. Any electrical guys know how to test one out?

Thanks

[1958 F.W.D.]

Check with VINELAND AUTO ELECTRIC in Vineland New Jersey, They have a website. Speak with JOE BERTINO, They specialize in antique alternators/starters/starterators, but most especially anything that was on Macks (a lot of Delco-Remy I believe...) Joe himself has restored several Macks. Good people. Not the cheapest, but all of their stuff is TOP SHELF QUALITY and your work is done right the FIRST TIME.

[Gmerrill0516]

Souondds like a good lead. Thank you!

Greg

[Gmerrill0516]

Does anybody know who makes the one in the fire engines and maybe a part number?

Thanks

Greg

[Charlie Hatfield]

That system ( alternator with load coil is used for making 110 volts to operate electrical equipment. that mack should be positive ground.

[Gmerrill0516]

Ok, I'll swap her around and see what the current draw does with a positive ground. Hopefully I didn't cook anything...

Any other info or opinion is welcomed.

Thanks again

Greg

[yarnall]

I just had the recitifier rebuilt on my 405A. Mine was made by Leece Neville. It was done by Chestnut Hill Auto Electric near Lancaster PA. It cost $192. It was arcing out really bad when running. My truck won't run now, but that is probably a different problem. I don't know if that is what you have there though. You might have an internal rectifier on you alternator. Mike

[Gmerrill0516]

I swapped it around to positive ground today and the high current draw has gone away. I resorted to an aftermarket electric fuel pump to establish fuel flow and now I just need some spark...I'm going to file the points and set the gap as well as double check the coil wiring as it is different in the positive ground trucks according to the "Motors" book. With a little luck I'll get her back to life...hopefully at least one of the coils is good. I'll be sure to wire it all up properly with a fuse and with an easily reached shut down for the fuel pump...

Greg

[Loadstar]

Greg, Sounds like your gaining......best of luck getting her running!!!

[Charlie Hatfield]

Yes, it's always one thing at a time until you get them all straigthend out

[Gmerrill0516]

SUCCESS!!! I swapped in a better set of points and condensor along with a coil I had floating around (I think the condensor was bad). I also rewired her as the motors book said at the coils for positive ground and she fired up nice. I advanced the timing a bit by ear and she runs awesome! The charging system works well, she has 40+ pounds of oil pressure and the tachometer from the factory at the pump panel even works!

I'm going to keep checking things off the list like brakes! and with a bit of luck, we will be taking a ride before too long. I took a video and am working out getting it posted. Thanks a million for the tech support guys. Some sound advice really helps. I hope to eventually get it to pump too. One issue at a time....It's nice when almost two years of work pays off.

Thanks again guys!

Greg

[Charlie Hatfield]

Your success at getting it running again is what makes coming this forum board all worthwhile. You learn by doing, but get help when you need it!

[fxfymn]

That's great. Keep at it.

When you do the brakes make sure you check the lines closely for corrosion. If it has been awhile since they were worked on I'd think strongly about replacing all of the steel lines as well as the rubber hoses.

One trick for the pump is to put the truck in reverse instead of direct when you engage the pump to help free up any rust and crap from the impeller.

[609albert]

Charlies correct about brake lines ,on my first parade after getting our 54 mack one of the steel brake lines corroded in half ,nursed it home ,luckly I was local, the rubber lines are available at nappa.

[Gmerrill0516]

I do need to look the lines over pretty hard. I may just make new ones as you recommend. I will have all the components overhauled and new fles linew are in order. The originals are pretty stiff and I would be afraid to use them.

Thanks

Greg