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About Mdmccurr

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    Engine Started

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    Mooresville NC

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    U Model
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  1. I don't know why previous owner added that red wire. If you notice it is connected on the left side to a circuit breaker at the far end that is not connected to the others. It looks like that circuit on the far end is for Stop Lamp Switch (does that mean tail-lights?). Perhaps the red wire was added to bypass the accessory relay and provide power to the right bank? If that is true then it is not working now because I used a test light and both the red wire and entire right bank is not getting power with key on. It sounds like my accessory relay is bad and once I replace that I may find other problems.
  2. Hello everyone, I need some help in figuring out electrical issues on a 1978 U-model that I purchased. I have the service manual and a (generic) wiring diagram for mid-70's R/U model trucks but I am still having difficulty. The truck is a positive ground system. I have three questions: Question #1 The previous owner had disconnected the wire at the fuse panel that supports low air buzzer, low air warning light, and oil pressure gauge --- not sure why he did that. That loose wire (white) is shown in picture below near accessory relay. I reconnected the wire to a hot portion of the fuse bar (3 position bar shown in image) and everything seems to now work (buzzer, light, etc).....However -- I can't figure out where that wire was supposed to be connected. There is no label for buzzer on fuse bar, however wire length seems to indicate it goes somewhere on the right side (with 3 fuse positions), near the accessory relay Question #2 I assume that the way this is supposed to work is that the left fuse bar stays hot all of the time (with key off) and the right side of the fuse bar is only hot when the key is on. When I turn the key to on position, I hear the click in the accessory relay to suggest that it is working. However, the right side of the fuse bar does not activate and the right terminal of the accessory relay does not go hot. Does this mean accessory relay is bad? Question #3 The headlights and outer marker lights of this truck stay on even when light switch is in off position (and key is off). Movement of light switch to on position does also turn on the dash lights and tail lights...headlights continue to stay on regardless The only way to get headlights to turn off is to disconnect the battery. Any ideas on questions above? Much appreciated! We saved this truck from the weeds (had been abandoned) so previous info is limited. It runs great aside from these electrical issues. Picture of fuse bar is attached below
  3. Thanks everyone for the info....I will make some calls and post updates
  4. Hello Mack experts, I am restoring a 1978 Mack U Model Tractor with the 237 engine. Unfortunately the Radiator is leaking pretty bad and probably needs a new core. We tried "Stop Leak" with only temporary success. I found a guy on Craigslist who is parting out a 1978 R Model Tractor. He wants $500 for the radiator. Is this a reasonable price for a used Radiator and does the radiator on an R model fit the U Model? Most modern radiators are "throw-away" and there are fewer shops that actually rebuild radiators anymore. Any idea how much it would cost to have a R/U model radiator redone? I appreciate any advice. Thanks, Mike
  5. Thanks everyone for the excellent advice. This truck has an interesting history. My father was the VP of Maintenance for Overnite Transportation back in the 1980's. When Smith Transfer went bankrupt in 1988, he was instructed to go to the bankruptcy auction and buy as many of these Mack U models as he could for city service in the Overnite fleet. He bought roughly 200 of them and had them all repainted blue/gray and restored to new condition in the Overnite shops. He retired long ago but last month we saw a Craigslist ad for this old truck that had been abandoned in Wilkesboro, NC, and recognized the paint scheme as Overnite. The truck had been sitting parked in a field for over 11 years but we simply put a new battery on it, fresh diesel and it fired right up in less than 5 minutes! It's going to be a project to bring it back to life but it is amazing how durable that truck is. Minor rust on the floorboard, rotten air hoses and a leaking radiator is the only mechanical issue that we have seen. Certainly needs paint and body work but the bones are still solid. I have attached some pictures and will post updates regularly. Thanks for the help! Mike
  6. Greetings everyone, I just bought a 1978 U-Model Mack that was formerly operated by Overnite Transportation. The truck is in great shape with only 278,00 miles. Unfortunately there is a small amount of rust in the floorboard between driver's seat and door sill and also at the base of the accelerator pedal. The base of the pedal is completely disconnected because where it normally attaches is a rust hole about 3 inch diameter. The rest of the floor is solid. I have looked underneath and everything looks fine from the bottom, just rusted in those 2 small locations. What is the correct repair for this? Pictures attached. Should I just cut out the damaged area and get some sheet metal and weld over the hole? Apply rustproof from the bottom? Thanks for your advice
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