mattb73lt

Having some issues uploading these pictures. Just tried from my phone, too. They seem downloadable, then you should be able to open them on your computer. I’ll try again tomorrow morning. Sometimes they will load after waiting a little while. Just saw your post about changing to a 12V starter and alternator. The diagrams will still be useful, but you're going down a much easier and reliable path now.

Here are some photos of the wiring diagram. I tried to zoom in on the S/P switch. This will hopefully help and the internet won't degrade the resolution to a point where you can't make them out.0D50EE72-8BCB-4EE4-BABA-13378E81E656_1_201_a.heic2AF4430A-2BC0-4FA3-8F0E-0B8E65AB3061_1_201_a.heic6C9893B1-B022-4782-95E3-8B7D9755EF40_1_201_a.heic

These trucks were positive ground from the factory. The two I have both were set up to run twelve volt starters with negative ground. The B42 had no series parallel switch originally and I deleted it from the B73 before I ever ran it. Two things I had to do when setting them up was reverse the leads to the ammeter so it read correctly under charge, if not it'll read a discharge when the generator or alternator comes on line. One way to test for this, is before running the truck, is to put a load on the system by turning the headlights on and checking the ammeter for a discharge or just momentarily giving it a direct short to ground downstream of the ammeter. If the polarity is wrong it'll show a charge.The other was to when I had the generator rebuilt I asked to have it set up for negative ground. Regarding the voltage regulator, almost every one I had new out of the box, had instructions on them to "Flash the Field". They are not polarity sensitive until the field side is momentarily energized only for a second or two. All the instruments and senders don't care about the polarity and will work normally with either polarity, with the exception of the ammeter. Looking at your diagram, it looks like it's set up for negative ground. The lead from Battery A is going to the ground side of the starter. I have a wiring diagram in an original Mack maintenance manual I used to wire and convert the B73 to the 12V starter and switch to an alternator. The new harness I had was set up for the S/P switch and a generator and I wanted to delete it properly and switch to an alternator. Let me dig that out and see if I can post it here to help you chase the wires to the switch. You can hook the batteries up to the S/P switch but leave the starter disconnected. Using a voltmeter, test the various smaller terminals for 12 volts, nothing should read to the starter lead. This would be testing the S/P switch in the "run" position. Using a jumper or pressing the starter switch with the ignition switch on should give you 24 volts at the starter on the voltmeter. That would test the S/P switch in the "start" position. To be clear, you're not changing your polarity so if the batteries are hooked up wrong the ammeter will be your initial clue they need to be reversed by putting that load on or creating a momentary short. You have a new S/P switch installed so it should work if wired correctly. Once you get it running I would still check that both batteries are charging by receiving around 14.5 volts by checking them with a voltmeter individually. That's one of the issues a S/P switch will give you, is that one set of batteries is not charging. P.S., I have a brand new 12V AC Delco voltage regulator still in the box if you want it? I bought it years ago and have no need for it as I have alternators on everything, now.

I wish there was a straight forward process for registering a vehicle in Connecticut. I put the requirement of the DOT number exemption in the same category as the Affidavit requirement I was asked to produce. I have several friends that had to get the DOT exemption, prior to receiving a registration, but on both my trucks I was never asked to produce one. That was as recently as 2023 for the B73. My fall back whenever asked to produce some sort of documentation, is to ask for the statutory requirement for such. Then ask for a supervisor for clarification on where the requirement exists if it cannot be resolved with that clerk. Many times they can't define the requirement as it's just what they've been told and can't be backed up in black and white. DMV requirement have changed over the years, mostly with vehicle inspections leading to just a VIN verification, and I've stated the requirements as I've experienced them to register a former commercial vehicle with Classic Vehicle plates in Connecticut. I would be curious as to what you actually experience and if they provide you with written documentation requirements? If you do make any phone inquiries prior to going to DMV, please tell us the context of those conversations and the statute references if they exist? That would certainly be helpful as a guide for helping people in similar situations going forward. As always, I try to be pleasant during exchanges with DMV, whether in person or over the phone. The person I spoke with over the phone was able to confirm my requirements was very helpful in getting my truck registered. There was still some confusion with the clerk and supervisor at the counter. But, after some back and forth, I did walk away with my registration and plates. Matt

Egge Machinery Company for pistons and rings. (egge.com) Manufacturers of custom pistons rings and many other internal parts. Olson Gaskets for all the hard to find head gaskets. (olsonsgaskets.com) Many NOS and new gaskets in stock Both companies are excellent with their products and helping customers. I've used them both over the years.

Wow, that one is nice, great paint. The cab is a lot different. It appears to be a standard truck cab, with the necessary fire truck add ons. The truck you pictured has a much widened and contoured cab.

405A 1019, that's off the door. I haven't verified it off the frame yet.

That's too bad. I think I was only there for about 15 minutes total, barely time to finish the last few swigs of my coffee, and they were done. The guy walked out put it on and walked away.

Picked up the B73 a couple of weeks ago from storage. Needs service and a big cleanup, still. Still tweaking little things with it. Added some seat belts to it. Re-did the bumper nickname "KRACKERJACK" in vinyl letters after the painted letters proved a lot less durable than I hoped. It was a gamble doing it, but the trip home from Macungie last year in the rain gave it a real beating. Just had it put on this morning at a local sign shop and it took barely five minutes to do. I actually think it looks better and stands out more than the old sign. Been busy with a lot of other projects over the winter, like managing a project for my employer with recommissioning a 1953 Mack fire truck to roadworthy status. Just mechanical and electrical work until he figures out what he wants to do with it. Took on my cousin's '54 M38A1 for some mechanical work. I generally don't work on other people's vehicles, but he begged me and threw some cash at me to do it. Mostly finished all the work on the '41 ford cruiser for the CT State Police Museum and it had several big reveals over the St. Patrick's Day parades, participating in some big ones in Hartford and New Haven. Lots of coverage of it for the museum. So all my hobbies are keeping me busy while i still work on call for a great employer at this point in my life. I can't wait to see what shows I can make it to this year!!

I'm planning to go, but I never know until last minute.

Looks awesome!!

Great news, sounds awesome!!!

Matt Pfahl's shop just rebuilt three AB engines and transmissions for trucks the Nuss shop is restoring.

Haggerty for all my vintage vehicles. I've had J.C. Taylor and a few others, Haggerty has been the most responsive and has the fewest restrictions.

The ENDT 673 was used to repower the M54 series of military 5 ton trucks during Vietnam. I've see pictures of a marine version of the END673 installed in a boat, so I believe there was a marinized version of it and I think some earlier engines, too, were installed in marine applications.