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AirHead1966
Samba Member
Joined: October 17, 2019
Posts: 568
Location: Triad Area NC
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 Posted: Wed Mar 24, 2021 6:23 pm Post subject: Re: Accessory Mode for the VW -Save your Pertronix |
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| Glenn wrote: |
| AirHead1966 wrote: |
| Glenn wrote: |
Why not just wire things to bypass the key?
That's the way VW did the radio. |
What’s the fun in that? 
This gave me something to do, plus I like no power to be on when I turn off the key. |
Install a master cut off on the battery. It also acts as a anti-theft feature. Adding relays is just another part to fail that leaves you on the side of the road.
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Glenn, I agree. Relays do fail. In this particular case however, it won’t matter if it did fail while on the road. All I will have to do is to bypass this whole thing just by moving the coil wire back to its old spot in the fuse box. That’s all and I will be back in business again! |
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balljoint
Samba Member
Joined: March 28, 2016
Posts: 166
Location: Tobago
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| Posted: Wed Mar 24, 2021 6:30 pm Post subject: Re: Accessory Mode for the VW -Save your Pertronix |
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| AirHead1966 wrote: |
| balljoint wrote: |
Have you gotten this to work successfully? |
Short answer, yes.
Long answer, I left the power connected when I was bench starting the engine after refreshing it. I put this circuit together and used it for subsequent engine starts on the bench. So, it does work. Should work the same when I put the engine back in the car. |
Ok good.
What you're doing is putting the primary of the ign coil in parallel with the coil of the relay hence dropping the total resistance. Don't know how much of an effect if any this will have on the firing.
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Glenn 
Mr. 010
Joined: December 25, 2001
Posts: 76935
Location: Sneaking up behind you
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| Posted: Wed Mar 24, 2021 6:31 pm Post subject: Re: Accessory Mode for the VW -Save your Pertronix |
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I actually like having an unswitched 12v power. That way when camping the night before a show, I cam play the radio without the key in the ignition. And leave my phone in the car charging over night with the car locked and the key in my pocket.
It annoys me that my 2018 Subaru only powers the USB ports when the key is in. So i can't charge my phone unless the key is in and on accessory.
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74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
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GARRICK.CLARK
Samba Member
Joined: June 30, 2012
Posts: 1267
Location: Lancashire UK
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| Posted: Thu Mar 25, 2021 1:27 am Post subject: Re: Accessory Mode for the VW -Save your Pertronix |
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| How about rewiring the accessories to permanent live. I've done it to mine. No need to turn the key on |
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Q-Dog
Samba Member
Joined: April 05, 2010
Posts: 8700
Location: Sunset, Louisiana
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| Posted: Thu Mar 25, 2021 5:51 am Post subject: Re: Accessory Mode for the VW -Save your Pertronix |
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| GARRICK.CLARK wrote: |
| How about rewiring the accessories to permanent live. I've done it to mine. No need to turn the key on |
I put a switch under the dash for the radio to select from key switched to always on. Most of the time it stays on the key switched position.
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'69 Dune Buggy
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EVfun
Samba Member
Joined: April 01, 2012
Posts: 5481
Location: Seattle
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| Posted: Fri Mar 26, 2021 3:38 pm Post subject: Re: Accessory Mode for the VW -Save your Pertronix |
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| mikedjames wrote: |
BTW there is a simpler version using two diodes and a single relay. I sketched it here - the diodes steer current to the coil of the relay either from the starter wiring, or from the output of the relay. Turning off the coil feed will de-energise the relay as with two relays.
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I suspect that will fail after the second or third time you turn the car off. When that relay turns off the energy stored in its magnetic field really wants to go somewhere. It could easily hit 100 volts with diodes trapping that reverse pulse when switched off. The 50 volt diodes are going to die, I predict the one going to the starter first.
A tranzorb across the relay coil, or a few other ways with a 1n4002, would allow it to work well. I built a small board to integrate brake lights and turn signals in the back and/or turn signals and parking lights up front. The 2 relays had tranzorbs across the coils to dampen the spikes because I doubt the 3 wire turn signal switch was rated for switching off inductive loads.
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| Wildthings wrote: |
| As a general rule, cheap parts are the most expensive parts you can buy. |
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Dale M.
Samba Member
Joined: April 12, 2006
Posts: 20379
Location: Just a tiny bit west of Yosemite Valley
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| Posted: Fri Mar 26, 2021 7:05 pm Post subject: Re: Accessory Mode for the VW -Save your Pertronix |
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| EVfun wrote: |
| mikedjames wrote: |
BTW there is a simpler version using two diodes and a single relay. I sketched it here - the diodes steer current to the coil of the relay either from the starter wiring, or from the output of the relay. Turning off the coil feed will de-energise the relay as with two relays.
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I suspect that will fail after the second or third time you turn the car off. When that relay turns off the energy stored in its magnetic field really wants to go somewhere. It could easily hit 100 volts with diodes trapping that reverse pulse when switched off. The 50 volt diodes are going to die, I predict the one going to the starter first.
A tranzorb across the relay coil, or a few other ways with a 1n4002, would allow it to work well. I built a small board to integrate brake lights and turn signals in the back and/or turn signals and parking lights up front. The 2 relays had tranzorbs across the coils to dampen the spikes because I doubt the 3 wire turn signal switch was rated for switching off inductive loads. |
There are relays with the transzorb diodes built in....
Dale
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AirHead1966
Samba Member
Joined: October 17, 2019
Posts: 568
Location: Triad Area NC
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| Posted: Fri Mar 26, 2021 7:29 pm Post subject: Re: Accessory Mode for the VW -Save your Pertronix |
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That’s why I did not use diodes at all  . |
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AirHead1966
Samba Member
Joined: October 17, 2019
Posts: 568
Location: Triad Area NC
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| Posted: Tue Apr 13, 2021 3:54 pm Post subject: Re: Accessory Mode for the VW -Save your Pertronix |
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To wrap it all up, now that the engine is back in the car and everything is running great without leaks, I installed the accessory mode circuit.
I also added a bypass mode switch that bypasses the entire circuit in case a relay dies on me.
To install, I added appropriate male and female spade connectors so that it just plugs into the existing wiring harness, fuse block and ignition switch without cutting or splicing any wires. Can be removed in a minute and original wires can be plugged in as before, but with the bypass switch, does not need to be removed.
Works just as I had designed it to work. No issues with it at all. No more burned out Pertronix!
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