hicrop10 Posted January 16, 2021 Share Posted January 16, 2021 I have a 79 r model,and was wondering if it needed that ground wire that went from the starter to the frame?I can remember them always getting broke.Tks.Mike Durkin. Quote Link to comment https://www.bigmacktrucks.com/topic/65550-79-r-model-ground-wire/ Share on other sites More sharing options...
terry Posted January 16, 2021 Share Posted January 16, 2021 27 minutes ago, hicrop10 said: I have a 79 r model,and was wondering if it needed that ground wire that went from the starter to the frame?I can remember them always getting broke.Tks.Mike Durkin. can give you some problems without that ground terry Quote Link to comment https://www.bigmacktrucks.com/topic/65550-79-r-model-ground-wire/#findComment-467049 Share on other sites More sharing options...
hicrop10 Posted January 16, 2021 Author Share Posted January 16, 2021 I have notice that if I leave it sit to long the batteries go dead.Going to make sure the ground is good.If that doesn’t take care of the problem then I move onto the heater switch,it seems that it shut off after about 10 minutes of running. Quote Link to comment https://www.bigmacktrucks.com/topic/65550-79-r-model-ground-wire/#findComment-467068 Share on other sites More sharing options...
Rob Posted January 17, 2021 Share Posted January 17, 2021 You really should replace that ground cable right from the starter motor housing to a clean and bare spot on the frame, then paint over the connection to keep it corrosion free. Even better yet run directly to the negative battery terminal via a "flag" terminal, or direct termination. Inrush current on a cold start can top 1200A until the engine gets to spinning and then decays rapidly. However this inrush current needs the least resistant path, (electrically) for efficient electron flow. This is where heavy gauge cable, (2/0AWG minimum) is a large player. If this cable is missing or compromised severely, the inrush current travels through the frame of the truck to the engine which is bonded marginally to the frame via it's mounts. Lots of resistance to electron flow here which causes rapid heating of components shortening their lifespan. If you heater blower motor is shutting down after a few minutes of operation ensure the heater coil, (core) is clean, and the motor itself is lubricated. The motor requires airflow over itself from the outside to cool and if the airflow is impeded, it can shut down temporarily till it cools. I'd remove the motor and while holding it in your hand, spin the squirrel cage with the other hand. If it is not freewheel turning, it is most likely binding in it's bronze end bearings when warm. You can usually tell this symptom by touching the motor housing just after is shuts down and it will be HOT. This is usually caused by the oil gone away from the "OilLite" bearing bronze bushings pressed into the end bells of the motor. Some you can take apart and relubricate with SAE30 oil, some require replacement. I'm still wet behind the ears however, so all that is just a guess. Rob 1 Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/65550-79-r-model-ground-wire/#findComment-467081 Share on other sites More sharing options...
hicrop10 Posted January 17, 2021 Author Share Posted January 17, 2021 Is this the harness that I’m talking about?I found it in my old stock.Checked my truck and it doesn’t have the ground wire I’m talking about. Quote Link to comment https://www.bigmacktrucks.com/topic/65550-79-r-model-ground-wire/#findComment-467117 Share on other sites More sharing options...
terry Posted January 18, 2021 Share Posted January 18, 2021 Yeah that should be fine for a ground to the frame. also need a good ground from frame to cab. terry Quote Link to comment https://www.bigmacktrucks.com/topic/65550-79-r-model-ground-wire/#findComment-467133 Share on other sites More sharing options...
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