two wires to positive side of HA coil

[Hubert64]

Hello,

Owner of a Viva HA 1965, I noticed that two wires connect to the positive side of the coil.

When I switch the contact on, the reading on the voltmeter is between 12 and 13 volts on the positive side of the coil.

When I disconnect both wires and leave the contact on, on one wire the reading stays the same (between 12 and 13 volts) and on the other, the reading falls to about 1/10 tenth of a volt (0,1 volt).

Could somebody tell me the use of this last wire where there is only 1/10 volt. Could it be because there is a built in resistance in the loom (ballast) ? What would happen if I disconnected that wire from the coil ? Thank you for your attention.

Hubert 64.

[Bob perry]

Hubert, do you have a positive or negative earth system?
Either way there should be a ballast resistor bolted on the coil.
If its a 1965, it is probably positive earth, although two wires suggests it is negative earth.
Later HA's were negative earth, as my 1966 model is.
The + terminal on the coil should have a ballast resistor fitted. It is NOT inline resisted like later Viva models!.
You should have a white wire and a white/blue wire. White/blue wire goes direct to coil + terminal, and white wire goes to the other side of the ballast resistor which bolts on to the coil + terminal also.
Can't do photo links, but I'm sure someone else can help.
Anybody confirm that?

[droopsnoot]

Is the second positive wire coming from the starter motor as it does on the HC? The idea on HC because it has a resistance in the loom is that the coil gets an un-resisted 12v via the starter to help the spark during cranking.

[Bob perry]

There is no resistance in the loom on HA's, that's why there is, or should be, a balance resistor on the coil.

[Hubert64]

Hello Bob,

Thank you for your answer. My Viva Ha Deluxe 1965 is negative earth. Concerning the colours of the two wires, I'll check up this evening and inform you tomorrow.

But there is one very precious information in your message : in an Ha, the ballast resistor is never in the loom but bolted to the coil (like the pictures in the Haynes manual show). I'm sure my coil has no such ballast. It is a Valeo coil I bought new about a year ago at an auto jumble. The coil it replaced had no visible ballast either.

Thanks again,

Hubert.

[droopsnoot]

There is no resistance in the loom on HA's, that's why there is, or should be, a balance resistor on the coil.

I did see you'd mentioned that, but whether it's physically in the loom or bolted to the side of the coil, it's still effectively in series with the power feed to the coil of course, and I just wondered whether the second wire was a starter bypass. Perhaps not a standard one, as it sounds like there may have been some modifications if the ballast is missing.

[Bob perry]

On a standard set up the White/blue wire does, indeed, come from the starter solenoid and goes direct to the coil. (Number 49 on wiring diagrams.)
White wire, (Number 11 on wiring diagrams) comes from the ignition switch and to the other side of the ballast resistor which is bolted on to the + side of coil on top of the blue/white wire.

As to any modification having taken place in the past, I couldn't comment, and it needs checking out by an auto electrician if unsure.

[Hubert64]

Hello Bob,

I verified. There is indeed a white blue wire (number 49) going to the plus side of the coil. When I put the contact on, it reads about 0,10 volts. From your answer, I gather it is the wire coming from the starter solenoid. What is the use of that wire ?

The other wire coming to the coil is white (number 11) and with the contact on, it reads between 12 and 13 volts.
There is no ballast between that white wire and the coil.

The resistance of my coil is between 4 and 5 ohms, which is the measure indicated in the Haynes manual for a normal coil (not a cold starting coil with ballast). Is it possible that some cars left the factory with coils with no ballasts ?

Best regards,

Hubert.

[droopsnoot]

I verified. There is indeed a white blue wire (number 49) going to the plus side of the coil. When I put the contact on, it reads about 0,10 volts. From your answer, I gather it is the wire coming from the starter solenoid. What is the use of that wire ?

If you have a ballast resistor in series with the coil, the coil is designed to run on (and usually receives) a voltage lower than 12v (because of the resistance) - I forget whether it's 9v or 6v. When you crank the engine, the load on the battery will often drop that figure down to a level where it is not sufficient to produce a spark strong enough to start the engine. So there is a wire from the starter solenoid that bypasses the ballast resistor and, during cranking only, provides the full 12v (which is often down to around 9v due to starter motor load) directly to the coil. Once you let go of the key, the coil reverts to running on the lower voltage via the resistor.

That's just a general thing with ballasted ignition systems, I don't know how the rest pertains to HA. Could the car have been modified in the past, to have the 12v coil and no resistor? I don't think it matters, the problem comes if you remove the resistor but leave the coil expecting the lower voltage.

[Hubert64]

Hello " Droopsnoot",

Thank you very much for your last message that answers my questions perfectly.

Best regards,

Hubert.