Mallory misses with headlights/and or blinkers on.

[TRN9]

Hi Folks!

Its been smooth driving for a few years! Missed ya'll! OK! I need your help! I have some weird freaky electric problems!

I have a '72 with a Mallory Unilight and when driving at night with the headlights on the bus starts to miss and when the turn signals are used the bus jerks with the beat of the turn signals.

I have replaced my Battery- It was old and not holding a charge well. Replaced the VR and replaced the coil with a new Bosch Blue coil.

Still the same problem- I was suspecting low voltage that the Mallory didn't like.

Here is the laundry list of what I have tried:

I have cleaned all power cables and the transmission ground strap.

Tested the voltage with the engine running and get 13.4V and 12.2V when the headlights are on.

I also disconnected the tach as I read on another forum that it could reek havoc on the coil signal...... Did not help solve the problem.

Lastly tested the coil and have ZERO primary resistance between #1 and #15 terminals. This was done with all connections disconnected.

So whats going on?

My first thought is that the coil I have does not have an internal resistor and has damaged the Unilight. But.... shouldn't it have some resistance, is it shorted out? If so how did that happen?

Thank you in advance for the help!
_________________
'72 Panel ~ B-Bus
************************
Camper Special Club Member
************************

[airschooled]

Unlike any other distributor I've seen, the Mallory requires a separate ground. How is yours grounded? And are the connections clean?

Robbie
_________________
Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com

[TRN9]

Hi Robbie!

I have a ground wire going directly to the fan shroud and then a piggybacked wire to the ground of the battery.
_________________
'72 Panel ~ B-Bus
************************
Camper Special Club Member
************************

[mikedjames]

Burnt 'run' contact on ignition switch/weakening battery, the coil/ ignition supply voltage may be dipping quickly more than your volt meter shows (A DVM measures about 3 x a second if I remember correctly) , and the Mallory may be disturbed by a sudden dip in the supply voltage.

The dip will happen when the cold filaments of the light bulbs are connected by relay or flasher to the battery circuit.
The inrush current will be a lot more than indicated by calculation from the rated wattage of the bulbs which is when the filaments are white hot.
_________________
Ancient vehicles and vessels

1974 VW T2 : Devon Eurovette camper with 1641 DP T1 engine, Progressive carb, full flow oil cooler, EDIS crank timed ignition.
Engine 1: 40k miles (rocker shaft clip fell off), Engine 2: 30k miles (rebuild, dropped valve). Engine 3: a JK Preservation Parts "new" engine, aluminium case: 26k miles: new top end.
Gearbox rebuild 2021 by Bears.

1979 Westerly GK24 24 foot racer/cruiser yacht Forethought of Gosport.
1973 wooden Pacer sailing dinghy

[SGKent]

What others said sounds logical - if the resistance across the ignition switch is getting worse it would pull the voltage down.

I found this on their website regarding the setup.

[airschooled]

Oops, I totally goofed on the initial read. Thanks smartphone……

Yes, you MUST HAVE a ballast resistor if your coil has no internal resistance between posts #1 and #15. Most new blue coils have 3.4 ohms built in though, are you sure you measured correctly?

It might be easier to find a correct 12v 3.4ohm resistor coil than to find a separate ballast resistor these days. Most old American iron used them though; do you have any hotrod friends?

THEN when you have the resistor, you can keep going if the problem persists. We'll go there when you get there.

Do not drive with the Mallory until then; you could burn it out, and new ones are not available anymore.

Robbie
_________________
Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com

[TRN9]

Well I found out that I am grossly incompetent at using volt/ohm meter. I found a dual ballast resistor through the local flaps and when measuring the resistor to figure out what side of it to use my meter still read zero. Derp! I had the meter at 20K instead of 200.

Yay! My coil DOES have a primary resistance of 3.4!

I am running a hot start relay, because the stock wiring is no longer capable of doing the job.

From what mikedjames posted and my need of a hotstart relay leads me to believe that the keyed power to the coil is not handling the load. Is it time for another relay to get power directly to the coil from the battery? Or is my alternator only putting out the correct voltage but not enough amperage?

I am mediocre at this electronic stuff so please explain what y'all think in simple stupid terms.
_________________
'72 Panel ~ B-Bus
************************
Camper Special Club Member
************************

[airschooled]

Oh good, we can proceed now with both of us totally goofing once.

The quickest and easiest way to diagnose key switch/wiring deficiencies is to run a wire straight from the battery positive terminal to the coil positive #15 terminal every time you start the car. You will need the key to start, and once you hook up the wire you will need to remove the wire to kill the engine because the key will not. (Don't leave the wire connected without running the engine or you can burn up your points.)

Try that and report back.
Robbie
_________________
Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com

[TRN9]

Hi Robbie!

Well I ran a jumper cable from the battery to the #15 terminal on the coil and the problem is SOLVED!

It is mind blowing at how much better my engine is running now!

Now I need to dig out my wiring diagrams and decide to run a new cable from the ignition or...?

Since I have never set up a relay for my electric fuel pump I am thinking now is the time. Maybe run the fuel pump and terminal #15 on the coil??

What do you think?
_________________
'72 Panel ~ B-Bus
************************
Camper Special Club Member
************************