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Fri Dec 03, 2010 10:25 am

mondshine wrote: It seems to me that the best place for this "master fuse" would be under the back seat at the voltage regulator between terminal 30 (B+) of the regulator, and the heavy red terminal 30 wire that powers the fuse panel bus that's always hot.
That way, the ignition switch and the terminal 15 wiring to the coil would be protected against a direct short.
I would think a 30 amp fuse would be enough to prevent nuisance tripping without sacrificing protection in case of a direct short (versus an overload).
Good luck, Mondshine

Thanks!

I think this is just what I am looking for...

... that is, if placing a fuse here would protect the coil circuit and prevent damage (to the ignition switch and wire to the coil) were any of the wires (coil +15, cutoff, auto choke, backup lights) were out ground accidentally.

I guess this fuse would protect a lot of other wiring too - right?

I also like the fact that this fuse would be "hidden" under the back seat.

What would be the best inline fuse & holder to use - an old "VW type"... or a modern blade style fuse (the ones encased in plastic)?

Fri Dec 03, 2010 1:22 pm

I believe that the greatest danger (if there is any) is from heavy gauge wire connectors popping off of their lugs and grounding to the chassis, or the insulation being chafed from vibration, causing a short to ground.
The problem with adding a fuse to these heavy wires is that the load capacity of the fuse needs to be adequate for the combined load carried by the heavy wire, yet low enough for the fuse to "blow" from a short in one of the lighter wires connected to the same bus.
My guess is that a 30 amp fuse would be adequate, but you might require more.
I prefer the ATC/ATO blade type fuses because they make a positive connection, and they're easy to get.

If you choose to add this "master fuse" I would test its function by momentarily connecting your coil terminal 15 to ground with the ignition switched on, to make sure the fuse pops. Carry a few spares.
Good luck, Mondshine

Fri Dec 03, 2010 2:49 pm

I want to rewire our buggy because of the lack of fused circuits.
What type of inline fuse holders should be used? Pics, links please?

Fri Dec 03, 2010 3:43 pm

Several years ago, I got frustrated with the corroded contacts in the fuse panel of my '74 Thing.
Here's what I did:

It's not for everybody; just an idea.
Good luck, Mondshine

Sat Dec 04, 2010 7:18 am

UPDATE: After thinking through this, I'm now re-posting, and now I think the better location for such inline fuse would be right where the wire to the coil attaches to the "hot" side of the fuse box. This location would prevent the wire running through the body from melting and taking out the ignition switch should that wire accidentily become grounded. So I added to mine an in-line fuse today, 10 amps. I put two spare fuses in the ash tray for storage. So my fuse holder is now in the trunk, near the fuse box; mine takes the old-fashioned glass fuses, as I had two in-line holders and some fuses in my garage.With the in-line fuse back by the coil, any grounding in that wire before the in-line fuse could still cause such damage; that location would only save from if that coil wire terminal accidently touched ground or became grounded - at the fuse box location it would cover everything.

And removing that fuse could be a slight theft deterrent.

Mon Dec 06, 2010 7:02 am

I see that someone suggested that also running a relay to the coil power would also improve the functions. Allowing more "power" to actually get to the coil instead of running from the battery to up front, then through the ignition switch and then all the way back to the coil.

I have always wondered about possibly over loading this wire as VW kept adding electrical load back there. First it was the coil, then the choke, then the fuel cutoff, then backup lights and on my bug, the power for the autosotick control (there is a dead short waiting to happen).

So if I install a relay in the engine bay, can I pull power from the battery connection at the starter? Just trying to figure out an easy power location. Of course, I would fuse this run too.

Now just to figure out which wire is the coil wire that comes off the fuse panel to the ignition switch. Will have to do some serious reading of the wiring diagram for my '68.

Mon Dec 06, 2010 7:55 am

I believe the black (terminal 15) wire from the main harness is adequately sized to power the coil, idle solenoid, and choke heater. Adding a relay would be adding unnecessary complexity which could be more detrimental than beneficial.
If you insist on doing this, the wire you want is the black wire of the main harness coming through the firewall.
The idea of fusing that wire, however is reasonable. I haven't done it personally, but I recognize the motivation. I still think the maximum protection would be gained by fusing the heavy red terminal 30 wire at the voltage regulator.
That way, the main power to the fuse panel and headlight switch, the ignition switch and the terminal 15 wiring to the coil would be protected against a direct short.
Good luck, Mondshine

Wed Dec 08, 2010 7:52 pm

Cusser wrote: UPDATE: After thinking through this... now I think the better location for such inline fuse would be right where the wire to the coil attaches to the "hot" side of the fuse box. This location would prevent the wire running through the body from melting and taking out the ignition switch should that wire accidentily become grounded. [b]So I added to mine an in-line fuse today, 10 amps.... at the fuse box location it would cover everything.

mondshine wrote: ... the wire you want is the black wire of the main harness coming through the firewall.
The idea of fusing that wire, however is reasonable. I haven't done it personally, but I recognize the motivation...
Good luck, Mondshine

Thanks Cusser and mondshine, thanks to your help I have now "found" that wire and will be doing this right away.

Question - would a 10 amp fuse be enough, thinking of going with at least a 16 amp red fuse... or maybe a blue 25 amp ?

Also, mondshine says:

mondshine wrote: I still think the maximum protection would be gained by fusing the heavy red terminal 30 wire at the voltage regulator.
That way, the main power to the fuse panel and headlight switch, the ignition switch and the terminal 15 wiring to the coil would be protected against a direct short.
Good luck, Mondshine

This makes a lot of sense and I will be looking into doing it... then if it works well, I'll remove the inline fuse to the wire to the coil that attaches to the "hot" side of the fuse box.

Wed Dec 08, 2010 10:07 pm

mondshine wrote: Adding a relay would be adding unnecessary complexity which could be more detrimental than beneficial.

Sorry but that's crap

Let your engine idle with the lights on and wipers on and check what the voltage reading at the coil is.
Turn on the hazards and stereo if you want to see it get even worse

A VW with a healthy alternator and a good ignition switch will be at 11-11.5volts max, now take a good size wire straight from the battery to the coil and do the same thing.
Mine read 13.7volt after that through a relay.
Have a look at the wiring of any modern car, they all run the igniton circuit through a relay and have done for decades so the ignition switch carrys no real electrical load like it does in a VW

You have to bare in mind that aside from the long wire lengths you have the coil, headlights (on 71 and later cars), wipers, turn signals, brakelights etc all drawing power through those tiny little contacts in the ignition , It's no wonder they burn out

If you had a totally stock electrical system in as new condition then you wouldnt notice that much difference but not too many people have that though.

Thu Dec 09, 2010 8:07 am

Joel wrote: mondshine wrote: Adding a relay would be adding unnecessary complexity which could be more detrimental than beneficial.

Sorry but that's crap

Let your engine idle with the lights on and wipers on and check what the voltage reading at the coil is.
Turn on the hazards and stereo if you want to see it get even worse

A VW with a healthy alternator and a good ignition switch will be at 11-11.5volts max, now take a good size wire straight from the battery to the coil and do the same thing.
Mine read 13.7volt after that through a relay.
Have a look at the wiring of any modern car, they all run the igniton circuit through a relay and have done for decades so the ignition switch carrys no real electrical load like it does in a VW

You have to bare in mind that aside from the long wire lengths you have the coil, headlights (on 71 and later cars), wipers, turn signals, brakelights etc all drawing power through those tiny little contacts in the ignition , It's no wonder they burn out

If you had a totally stock electrical system in as new condition then you wouldnt notice that much difference but not too many people have that though.

Ditto to this...Absolutely right...

I have seen the smoke from the ignition switch giving up on my car and one other!!!

My coil pulls about 7 amps....I fused it at 15 at the firewall.

Jim

Thu Dec 09, 2010 9:44 am

Sorry Joel and Baja-
You made a convincing argument.
I never thought of placing a relay there, and didn't know modern cars were wired like that.
Both of my ACVW's use a Mallory Hyfire CD ignition, so the point is moot for me personally.
My terminal 15 wire in the engine compartment only powers the choke heater, the idle solenoid, and provides the (tiny) switching current to activate the CD box. The CD box gets its (fused) power straight off of the battery.
With a CD ignition, the only wires to the coil primary are from the CD box itself.
So I stand corrected about the relay.
Good luck, Mondshine

Thu Dec 09, 2010 10:56 am

Just a little more info from me...

All loads (Amps) that are on the stock unfused wire that goes back to the engine coil is also used for the Choke and Idle Solenoid as mondshine stated.

The amps for all of those is around 7 amps not just the coil.

Most of our coils are around 4 ohms on the primary. 12/4=3amps
So you get a picture of amps...3 for the coil and the choke element pulls 3 or 4..The selenoid pulls very little...

As a note....I also added a relay for the starter solenoid....That's another current/amp hog.
If you relay both of those your Ignition switch will nearly last forever.

Jim

Thu Dec 09, 2010 12:56 pm

Not being electrically or mechanically inclined, both the last two posts mention power from the battery. But trying to get a power wire directly from the battery back to the engine compartment without drilling a new hole is not at all easy. I may have asked this before, but can one take power from the positive battery connection on the starter? And fuse that wire?

Thanks

Thu Dec 09, 2010 1:01 pm

I'm not electrically inclined either. Can someone take the final suggestion(s) and make some sort of diagram of this mod. Like where and what where to cut and splice? Sorry, I know all the pertinent info is above but I am not entirely sure I understand everything involved. A visual representation would be easier to decode. Many thanks.

Thu Dec 09, 2010 1:26 pm

John, here is a link to read and see if you are up to the task.

Although it is for a type 2 the process is basically the same.

Here is a pix of how he wired it, just for the starter solenoid.

http://www.type2.com/bartnik/relay.htm

See if you can understand what is said, then go to the Technical button, find your wiring diagram and see if you can identify the wire that goes to the starter and coil/choke/fuel cutoff.....Get familiar with the diagram and your actual wires....

If you are lost then you need help doing this project. You will need terminal lugs and the tools to crimp them, wire and shrink tubing.

Jim

Thu Dec 09, 2010 7:41 pm

i-cortin wrote: Cusser wrote: UPDATE: After thinking through this... now I think the better location for such inline fuse would be right where the wire to the coil attaches to the "hot" side of the fuse box. This location would prevent the wire running through the body from melting and taking out the ignition switch should that wire accidentily become grounded. [b]So I added to mine an in-line fuse today, 10 amps.... at the fuse box location it would cover everything.

Thanks Cusser, thanks to your help I have now "found" that wire and will be doing this right away.

Question - would a 10 amp fuse be enough, thinking of going with at least a 16 amp red fuse... or maybe a blue 25 amp ?

This makes a lot of sense and I will be looking into doing it... then if it works well, I'll remove the inline fuse to the wire to the coil that attaches to the "hot" side of the fuse box.

I drove it about 45 minutes Tuesday after I did this, didn't have any problems. However, I have a single Weber 40DCNF carb, which has no choke or choke heater, or any carb electrojet, so I don't know how many amps those could draw on a stock carb. I DID have it in reverse several times, so the back-up lights plus the coil did not blow the 10 amp fuse. I think a 15 amp fuse would be fine - you're just trying to have the fuse blow if it shorts out instead of having the wire melt.

On my sedan, late 1970s, I did have this wire melt, had to run a supplementary wire over the roof (held in place by rain gutter, just to get me home). That was not fun.

Thu Dec 09, 2010 11:42 pm

Here's a story.

Recently, I was sitting at an intersection. The light turns green, cars in front of me start to move, and the engine in my car dies. I'm stuck in the street, and can't start it back up. What happened was the hot wire going to the backup light switch got sucked into the fan and grounded out the coil. If it was fused, it would have blown, which could have been a big problem, but so is frying the circuit if there is no fuse.... bottom line it started and I safely got off the road to check it out.

Of course you should know the condition of your electrical system (I do now, believe me) but just a thought.

Back to the topic, I'm not completely sold on running the coil off a relay because it isn't getting enough power. Once you spin up the gen/alt it should be getting the voltage it needs. At least this is what my gauge says that measures power on the dash side of the ignition circuit.

Fri Dec 10, 2010 1:30 am

Lettuce, Sounds like you have some PO wire hackery happening.

The reverse lights have there own fuse and on all of my beetles its been about 2" after it leaves the coil on its own bracket off the coil clamp.
This was done so that reverse light problems didn't interfere with the engine

Also the wire should be no where near the fan intake.
It runs across the carby side of the shroud not the firewall side and has a tab the holds it on the right hand side next to the generator
Then down through the hole in the firewall tin

Oh yeah the alternator charge is not fed straight to the coil like you mention above, Its fed directly to the battery side of the ignition switch.
The coil still has to draw its power through the ignition switch along with the wipers, turn signals, brake lights, reverse lights etc

Fri Dec 10, 2010 3:39 am

tardis454 wrote: I want to rewire our buggy because of the lack of fused circuits.
What type of inline fuse holders should be used? Pics, links please?
If you want to stick with VW-style fuses for your inline fuse holder... try these from Wolfsburg West:
http://www.wolfsburgwest.com/cart/DetailsList.cfm?ID=111937093A
If you don't want to stick w/ VW-style fuses.... just go to your FLAPS and buy a fuse holder with the proper gauge wire for what you want to protect.

CarlIseminger wrote: I may have asked this before, but can one take power from the positive battery connection on the starter? And fuse that wire?

You CAN use the battery terminal connection at the starter. This is a VERY good source for battery power, but if you want to fuse the wire near the starter... it is a harsh environment for a fuse holder.

Another spot is the B+ terminal (the big one) on the alternator. This is the source that charges the battery. Expect it to be a little "hotter" than the battery. While running above idle the alternator should be putting out close to 14v to charge the battery. That is an extra 2v to the coil which could equiate to approx 300v more from the secondary coil output (assuming a 150:1 primary to secondary winding ratio).
The reason you can use the alternator output is because the internal/external regulator controls the output.
I think this applies to generators too, but I'm not 100% since the output of the generator goes to the regulator before going to the car's electrical system.

WARNING- If you choose to power your coil from a Bosch-style relay connected to the battery for power and the ignition wire (black #15) as a trigger... you may run into a condition where the coil remains powered even AFTER you turn OFF the ignition switch!!!!
This is because most Bosch-style relays are designed to remain CLOSED (flowing electricity) with as little as 5V.
It is often necessary in such configurations to add a 1A diode to the GEN light in the dash. Read this article:
http://www.mgexperience.net/article/mgb/ignition-run-on.pdf

Fri Dec 10, 2010 4:40 am

Doesn't apply to generators, Its all unregulated voltage coming from them, the proper regulated 12volt is the output of the regulator under the rear seat

ashman40 wrote: WARNING- If you choose to power your coil from a Bosch-style relay connected to the battery for power and the ignition wire (black #15) as a trigger... you may run into a condition where the coil remains powered even AFTER you turn OFF the ignition switch!!!!
This is because most Bosch-style relays are designed to remain CLOSED (flowing electricity) with as little as 5V.
It is often necessary in such configurations to add a 1A diode to the GEN light in the dash. Read this article:
http://www.mgexperience.net/article/mgb/ignition-run-on.pdf

Thats the beauty of relays, they take a bit of power to pull in, but once the coil is powered they take next to no power, a bloody watch battery could probably keep one pulled in but as above it has its down sides

My A/C fan was causing a problem with mine, if i had the A/C on when i turned the car off it took a couple of seconds before the engine stopped.
The A/C fan was acting as a generator once I turned the ignition off and kept the relay pulled in till it stopped spinning
A Diode fixed that problem