Ford Solenoid Hot Start installation instructions, Mark Henry's method Options

[Mark Henry]

Because this comes up so often I decided to make a tutorial on how I install the Ford solenoid.

The Ford solenoid fixes the common hot start problem of Bosch starter solenoid and it also reduces the load on the ignition switch. Although these instructions are for the 914 all aircooled VW's and Porsche often suffer from this problem and with minor changes this can be done to any car.

The issue occurs because the Bosch starter solenoid needs a full 9 volts to kick in. The combination of age, heat, corrosion, many connectors, a small ignition switch and wiring running to the dash and back can degrade the volts to less than the 9V required.
The Ford solenoid only needs about 3 volts for the 12V version and even less for the 6V which for our purpose works no problem.

My installation drills no holes in the car, not a single factory wire is cut, no in-line fuses, fully reversible and simple with no added bullshit.

Please this is not a discussion on if you prefer the wimpy (IMO) Bosch horn relay, want to cut and hack in a new wire or believe throat singing Vajrayana chants is a better method, start you're own thread.

Of course as with any electrical trouble shooting the first order of business is always clean all of your grounds and make sure the chassis to transmission ground strap is in place and in good condition.

I'll start right away with the money shot of the completed installation to show how clean this can be done.

[Mark Henry]

Just food for thought, or should I say math (IMG:style_emoticons/default/smile.gif)

Vdrop = IR, basic voltage drop law.

12v at 8 amps on a 12 foot run with 22awg wire will see a voltage drop of 25.83%.
That 12v is down to 8.9v, border line for kicking the Bosch solenoid.
That's not counting the resistance of the connectors, fuse box, switch, age, heat, etc.

I don't know the actual length of the run or if that's the correct size wire, etc., etc.....but its a good enough example to show that a DC circuit has substantial losses even when new.

note same calculation with 20awg wire loss is 16.25%
I'd say obviously heat is a major contributor as this is more than often a "hot start issue".