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.

This is a Ford solenoid very common fender mounted unit available up to 1967 in a 6 volt one small post version and up to the end of the 80's as a 12 volt 2 small post unit.
I recommend the type that has the bracket, the ones with the tabs are a PITA as you have to make a bracket.

This one is a used and 12V, but is nice because it is a made in USA solenoid. Now all the new ones are made in china. One person said they had a china made unit fail, but I've personally never seen it.
I've only ever had one fail in close to 30 years of doing this and that was due to corrosion after 8 years of hard winter driving.

First thing you need to do is enlarge the one hole so it fits onto the starter mount 10mm stud, you want to only cut the one side so you can't drill it. I use a burr on a die grinder, but this can be done with a round file.

Then cut the bracket about 3/4" to 1" as shown with a hacksaw.
I marked the bend and cut out to make sure it not only cleared the nut, but the socket as well, for ease of installation.

When making the bend in the bracket it is very important that you DO NOT stress the plastic housing of the solenoid. I use two vice grips to start the bend, then finish it up in my vice.

Once done you can hang it off the bottom starter mount stud to start the nut, then if you did your bend job correctly you can get a 17mm deep socket on it to tighten it up.
I mount the solenoid plastic side up just in case water gets into the solenoid, so that it can drain back out.

Ring connectors from your local FLAPS seem to come in two sizes, way too big and too small.
Get the too small ones made for 10 gauge wire, with the yellow ends.

The best method to enlarge the ring connector hole is to use a block of wood and a step drill bit as shown. Go slow and it does a nice job.
Note I have the connector upside down so that it catches on the end of the wood.

I hate the plastic sleeves on generic connectors so I cut them off, I'll be using heat shrink tube to finish them off. Please be careful cutting them off.

So these are the connectors needed, but in a brain fart moment I forgot the one female quick connector that is also needed.

The tab connector I had, I think it was on an old VW wiper assembly. Likely you can get them from McMaster-Carr but I think they only come in boxes of 100.
You can make one ghetto from a connector or fab one yourself by cut/drilling it out from some copper pipe although pipe is a bit too thick.


The hacked up ring connector shows how bad it gets trying to drill them with regular drill bits. Rack your fingers a few times when the connector catches and spins and you'll be out picking up a step drill bit PDQ.

For crimping the wires go out and get proper crimpers that put a dimple into the connector. Toss those POS cheap ass FLAPS or dollar store "crimpers" in the trash.

Here I'm using a fairly inexpensive Panduit crimper/stripper set I've had for years.

For the wire I'm using 10 gauge multi-strand primary wire.

I slide on heat shrink tubing, then crimp the one end on, then bend it to the shape I like.
Then I repeat for the other side. Don't forget to slide the tube on before crimping the connector.
You want to bend it so it doesn't touch the starter, as that could rub through the plastic wire covering and cause a short.

A tip to make a real nice job is to slide your HS tube on, bend your wire first and then heat shrink the tubing.

This shows how to connect the wire to the solinoid, dead simple.
There is no right or wrong way to do this, it's a simple switch, it will work in either direction.

if you are worried about the exposed hot positive you could find a boot that fits, here I used a simple end cap from a hardware store.

This shows your existing main battery stock wire that comes directly from the battery to the starter.

The factory yellow wire that was on the Bosch starter now plugs directly into the Ford solenoid.

Note that this one has two small posts you only need to use the one, this one seems to be backwards from most of the solenoids I've used. Only one side will work, so if yours doesn't work first time flip these around.

A couple of zip ties and you're done.

This is real simple to make and crimpers should be a tool in every car guys tool kit, but if if you really think there's a demand for this I could offer a complete plug and play wiring kit for something like $30 shipped USA and Canada.

If I were to offer a kit I'd look into using better strain relief connectors.
You would still have to buy a solenoid and do the mount mod.

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...

Mark - Thanks so much for the detailed documentation. It is indeed the RIGHT way to do it.

ADMINS - How does this get moved to the Classics?

Cheers!

It does belong in the Classics! Great job coming from a grump old rascal. Keep up the great work.

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.

thank you for sharing!

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

Thanks much Mark- on my way out to the garage...

I added a point about running the wire, make sure it doesn't touch the starter, as it could eventually rub through the plastic covering.
I've never seen it happen, but better to be safe than sorry.

Thanks Mark!

I mounted mine using a couple of hose clamps around the solenoid, but I like your method better.

Gary

I wonder if there's another design that would allow the solenoid to mount utilizing both ears rather than one? As the one side is at a constant +12 volts, I'd be concerned about vibration eventually causing the solenoid mount to crack and create a mother of a short if that terminal contacted the grounded metal. Perhaps a bracket using two of the transmission to engine mounting bolts would make a sturdier, vibration resistant design. Yes, I am a belt and suspenders type of guy, but have witnessed what happens when a battery positive terminal touches the metal of the body firsthand.

Still, great write up on the wiring for the solenoid.

A few more things to consider...
I like to use wire with a high-temp insulation around the engine. Some of the primary wire from the local auto store has PVC insulation that can melt pretty easy so make sure it can't get too close to hot parts. I like Teflon insulation, or maybe put heat shrink tubing over the full length for extra insulation.

I don't trust crimp terminals for anything high current or vibration. For some extra reliability you can wick some solder into the terminals.

The protective caps on the big terminals is really a good idea not just in case the relay came loose. An exposed terminal to the battery can be dangerous if you accidently got a wrench or screwdriver across it. I know someone who got his watch band on a starter solenoid terminal and it took a long time for the severe burn on his wrist to heal up. Of course he shouldn't have had a watch on in the first place.

Nice work Mark! Classic for sure.

Genius level hack.
Good on ya Mark!

I've never had an issue and one car I did, a summer DD, has had the same repair for close to 25 years without being touched. If you're worried about the nut coming loose just use some red loctite on it.
Same with the wires, since the solenoid is attached to the tranny it doesn't see a huge amount of vibration. If the solenoid was screwed to the body then I'd worry about the connectors and vibration.
I've also never seen heat as an issue as well.

Not my first rodeo, I've done this mod countless times since around 1990.

Nicely done Mark

Thanks everyone

Just to calm some peeps fears I did some housekeeping on my install and made it even better. I shaped the main battery cable so it runs right beside my wires, then I zip-tied the whole bundle together.
So that's a 3 gauge and two 10 gauge wires tied together, the thing is almost like a solid pipe. If the nut holding the solenoid on was to come loose the solenoid still isn't going anywhere.
Short of something catastrophic, like an axle failure, I'd say it's now bulletproof.

I know I've said I dont like to cut factory wires, but this is all part of my custom /6 conversion harness.
This is the custom end of the engine harness I made from an salvaged main harness and pins from an old relay board. My /6 engine is total plug and play with about 6 connectors and the relay board has been deleted.
The harness stays on the engine for R&R.

Finished installing the new "Ford" part- got it from Amazon for $20 shipped prime. A little different than the one above with only one small terminal- works great. Car cranked right over.

Thx Mark.

Now that looks very sturdy and it's a beautiful write up.

Great write up. And to think, the money you spend on the solenoid will prevent you from having to purchase six Chinese made ignition switches over the next year and a half...

It's a win-win.

I added a link to this thread in my signature.

Mark--very impressive write up/ conversion. Somehow I missed this earlier so thanks for sharing.

Jeff B

I bet the Cap'n would approve, but Slits would still bitch about something...

I miss them a lot, but your posts go a long way towards filling the gap they left.

Nice job

Cheers- Harry

The Ford solenoid is a great idea, and works with most applications. I would soldier the joints to keep from corroding and assure a long term connection. I worked on Brown trucks for 25 years so I can attest to the solenoid, but also the upgrade to solder as well. I really like the liquid electrical tape over the studs and any wire exposed to the elements as well.

Ok I'am in on this,is there a part number for the solenoid ? any idea if I could pick it up on the west coast so I can ship for a reasonable price to my country,thanks Mark.

Standard SS-558 is the 6V single small post, works fine at 12V and takes less amps to kick than the 12V.

Standard SS-588 is the 12V two small post, works fine. Also called SW3

I prefer the "Standard" brand name.

They sell Fords in NZ, you should be able to get it local.
They were on all kinds of cars and trucks, huge number of different manufactures part numbers.
Evilbay ads below have a list of vehicles. First link is 12V, 2nd is 6V:

http://www.ebay.com/itm/Starter-Solenoid-M...4xS&vxp=mtr


http://www.ebay.com/itm/Starter-Solenoid-S...3.c100033.m2042

Thanks Mark,most of our Fords come from Australia but having said that there is a lot of USA classic cars imported from the west coast so should be over to find one here,cheers

EDIT...got one on Ebay for less that $10 free shipped,NO way I could get one in my country for that,great write-up Mark .

One fail point I was told, but have no direct proof (anecdotal) was that a cheap Chinese relay had failed. That why I recommend the "Standard" brand of relay's.
I've never had a Standard relay fail other than the one that fell apart from severe corrosion. This was after 8 years of winter service on heavily salted roads.

Ha Ha funny ,Chinese ones are out there,really moved away cheap but not much cheaper ,rest assured got the Standard part ,thanks again.

The tabs are available at O'Reilly's Auto Parts in packs of 10.

BWD part # CT948. Under $6

Hey Mr. Henry- it worked!

Well, not at first... When I turned the key... nothing. Then I recalled you saying there's a 50/50 chance it would be either terminal (I had a two post version) so I switched the connection and "Viola"; success!

Click to view attachment

Much thanks- Harry

Hi Mark,
Surprised to see that no ground wire is needed to be attached to the non used terminal in your application of the Ford relay switch?

Because the metal bracket on the solenoid is bolted to the starter mounting stud, there's your ground for the solenoid.