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.

[jim_hoyland]

Great write up- Admins, please add this to the Classics
One question: how is the Ford solenoid different from using a 50 amp relay. Many hot-start kits and threads in The Garage use the smaller relay. Just curious as to the pros and cons... (IMG:style_emoticons/default/smile.gif)

[Mark Henry]

Great write up- Admins, please add this to the Classics
One question: how is the Ford solenoid different from using a 50 amp relay. Many hot-start kits and threads in The Garage use the smaller relay. Just curious as to the pros and cons... (IMG:style_emoticons/default/smile.gif)

I don't want an argument as to which is better but this is my logic:

1/ I've been doing this forever, not about to change. Before me guy's like Gene Berg have been doing it since the 60's, so this has been a mod done for over 50 years.

2/ The Ford solenoid is waterproof, at least damn water resistant, the SPST relay is not at all. So you must mount the bosch horn relay in the engine bay, run wires through the grommet, tap into a power source, use a fuse, drill a mounting hole and cut the factory wire or at least make an extension/adaptor.

3/ the SPST relay (bosch horn relay) may be 30-50amp which should be enough on paper, but it still has very small contacts. The Ford solenoid must be rated for at least 500 cranking amps, likely much more.

4/ I've personally only had one failure, one that was so badly corroded after 8 winters that the bracket/bottom rusted right off at the rivets and the solenoid literally spilled it's guts in my hand when I took it off.
I've replaced several perfectly good looking SPST relays with a ford unit.

Technically I guess you can say I've had two failures, as a rookie I bent the mount by reefing on the plastic housing and broke one. That's why I instruct you to only bend the mount using two pliers, experience.

5/ The solenoid is fastened to the transmission starter bolt, not the body, so there's almost no vibration strain on the wires.

6/Unless you run across a concours weenie who likes to crawl under cars, just to be an ass pointing out everything that is not factory on a person's 914, you're the only person that will ever know.

7/ When I turn the key the first thing I like to hear is a spinning starter.

8/ I'll think of more reasons, hold my beer.

9/ KISS, this is such a simple fix.

If any of you guys who can't stand the thought of a Ford part on a Porsche, but have a Rennshifter, well you better toss that puppy in the trash.
Jwest now makes all his parts, but the early versions were a modified Ford Mustang shifter. The basic design has not changed.
So send that puppy to me and I'll dispose of it properly, I hate them so much I'll even pay you the shipping. (IMG:style_emoticons/default/biggrin.gif)

[jim_hoyland]

Great write up- Admins, please add this to the Classics
One question: how is the Ford solenoid different from using a 50 amp relay. Many hot-start kits and threads in The Garage use the smaller relay. Just curious as to the pros and cons... (IMG:style_emoticons/default/smile.gif)

I don't want an argument as to which is better but this is my logic:

1/ I've been doing this forever, not about to change. Before me guy's like Gene Berg have been doing it since the 60's, so this has been a mod done for over 50 years.

2/ The Ford solenoid is waterproof, at least damn water resistant, the SPST relay is not at all. So you must mount the bosch horn relay in the engine bay, run wires through the grommet, tap into a power source, use a fuse, drill a mounting hole and cut the factory wire or at least make an extension/adaptor.

3/ the SPST relay may be 30-50amp which should be enough on paper, but it still has very small contacts. The Ford solenoid must be rated for at least 500 cranking amps, likely much more.

4/ I've personally only had one failure, one that was so badly corroded after 8 winters that the bracket/bottom rusted right off at the rivets and the solenoid literally spilled it's guts in my hand when I took it off.
I've replaced several perfectly good looking SPST relays with a ford unit.

Thanks for that clarification; makes good sense. Is there a part # for the type of solenoid you used above ? I'M going o switch out my "horn relay" for the Ford relay as y let your excellent write up