jake Posted November 15, 2006 Share Posted November 15, 2006 We have a 1980 and a 1986 Mack D M s. It seems thy both suffer from the same illness. Sometimes when we start the engine, only lights willwork. Nothing else. Not gauges, heater fan, radio, engine brake,or any thing that requires electrical power. Also when this occures, the volt meter shows no responce and you cannot hear the "click" of the relay that you normally hear. Today when this happened I stopped the engine and it would not crank when I tried to restart it. I let the truck set for five minites and it started right up with every thing working normally. I put a new relay on the 1980 but it didn't change anything. I work on them and drive them every day but this has me puzzled. Any ideas??? Jakebrake Quote Link to comment Share on other sites More sharing options...
HK Trucking Posted November 15, 2006 Share Posted November 15, 2006 Bad Ground to the cab.Had this happen once, ran a ground cable from a bolt on the frame to a bolt on the cab where the hood support fastens to. End of problem. Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment Share on other sites More sharing options...
Firemack Posted November 15, 2006 Share Posted November 15, 2006 Jakebrake,Could be the ignition switch, they have multiple contacts and might be the contacts to turn on the lights are OK , but the others are worn and not getting contact everytime. Other items: could be overheating from the battery cables and sometimes they have a thermal link which can shut down until it cools. Are all of the cables and terminals clean?My B model has the old style ignition switch and I noticed that my truck will start and run but the fuel and temp gauges and some of the lights don't always works unless I reset the ingnition switch. Being a firetruck it doesn't have a key, but you could be having a simlar problem.Firemack Quote Link to comment Share on other sites More sharing options...
MACKS Posted November 17, 2006 Share Posted November 17, 2006 I would check the ground wire that goes from the motor to the frame, I had that same problem on my DM and then it happened to my RD make sure the ends are clean and tight. Good Luck Quote Link to comment Share on other sites More sharing options...
jake Posted November 17, 2006 Author Share Posted November 17, 2006 Thanks for the replies.I will try both remidies.I have found over the years that when lights and things like that act weird that it is usually a bad ground. Also sometimes I can bring things to life by turning the ignition switch on and off several times. Kinda' makes me think it could be the ignition. Thanks again. jakebrake Quote Link to comment Share on other sites More sharing options...
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