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That was a voltage drop/resistor deal. After start would drop amps going to coil to not fry points.
Any idea why it would be on the side with the secondary battery or did it use both batteries to start and the second would become a auxillary battery after?
That looks like a Kelsey-Hayes resistor for their trailer brake controller. You would hook up the output wire to better tune the trailer brake response.
Do an ebay search for kelsey-hayes selective resistor.
john
I stand corrected, me and my 70 year old plus mechanic buddy that was staring over my shoulder stands corrected too.
I'll go back to my corner and be quiet now.
That's the notoriously unreliable Kelsey hayes resistor which is for trailer brakes and goes to a equally terrible hydraulic brake controller. Ditch the whole disaster before it sets the truck on fire or decides to spray you in the cab with brake fluid.
Any idea why it would be on the side with the secondary battery or did it use both batteries to start and the second would become a auxiliary battery after?
Ford did not offer dual batteries for F100/350's until 1973, so what you have is either aftermarket (usually installed by RV dealers) or installed by a previous owner. Gawd only knows what the parts came from.
Any idea why it would be on the side with the secondary battery or did it use both batteries to start and the second would become a auxillary battery after?
Back in the 1970's truck campers were popular. Many times an auxiliary battery would be installed to run the camper's electricity (with a switching device so as not to run the truck's battery down.)
That's the notoriously unreliable Kelsey hayes resistor which is for trailer brakes and goes to a equally terrible hydraulic brake controller. Ditch the whole disaster before it sets the truck on fire or decides to spray you in the cab with brake fluid.
I have run many trailer brake controller & adjuster just like that and never had any issues like that.
That is what you ran before ABS came out on cars & trucks and this would not work as it should.
There should be an adjuster part that run between the 2 long spring parts with a thumb screw to slid up & down to change resistance based on trailer loaded weight.
Most of my trailers were loaded be it car or TT and most of the time pulled by the same car or truck so I had no need to adjust this resister.
Dave ----
There are two types of Kelsey Hayes resistors that are commonly found. On the type you have the leads are attatched at different points to adjust resistance. The other type ( I have one), has a reisister coil in a U shape with a sliding bar on it for adjustment.
Warner and Teconsha offered similar brake controlers and NOS condition ones sell quickly.