Dynamo not charging battery. 1955 11BL

Hi Ian

It sounds like you have a break in the wiring somewhere. It’s ok to drive without the ammeter in the circuit – but whether it is safe really depends on the nature of the break. If, for example, a live wire has fallen off something and is flapping around loose, that would not be safe. If it’s a break inside the insulation then it’s ok. So I think you are right to want to investigate further.

It doesn’t sound like a problem with the ammeter or its connections if it can show a discharge. It must be something in the charging side. The replacement regulator may have the same problem as the original one.

Checking continuity will be more effective if you can get to the ammeter as it all joins wires together. It will be easier to find a broken wire if you disconnect the wires from the ammeter to buzz them out.

I don’t have one of these newfangled modern big boot cars with the two-tone dashboard. Taking the speedo out of the earlier cars is quite straightforward but your car hides the speedo behind the windscreen surround.

What follows is my guess as to how to get to the speedo from looking at the part manual which shows the surround to be in 2 parts. I guess you need to remove the escutcheon covering the windscreen opening mechanism to expose the lower screw and there’s a screw at the top which may or may not be covered. I think there may be some jiggling to release a clip on the side. That should allow the surround to be moved forward for you to get behind it. The speedo is held on the surround by a screw on each side.

Before you do any of this, of course disconnect the battery. I hope this helps.

Let us know how it really comes apart and what you find.

Chris

Ian,

Extracting the instrument cluster is less daunting than it sounds.  Yes, you do have to remove half the windscreen trim but it is a relatively simple job and Chris has pretty well explained the method …. even though he has never done it!

Plrase contact me if you run into a problem – I’m about 10 minutes away from you.

B….

I have the same problem Chris. The regulator is not switching over to the dynamo once the engine is running.  You imply that it might not be a regulator fault as I had supposed. If the ammeter is not registering is it not as likely to be the fault of the regulator as a wiring problem?  Is there a way to test the regulator before dismantling the dashboard?

If the ammeter shows a discharge when such tings as the lights are on, and shows no positive charging when the engine is running without the lights on, there a couple of possiblities.

We can rule out a broken connection in the ammeter circuit because a discharge can be shown on the ammeter.

If the ammeter needle moves in the negative direction but not in the positive direction, I suppose it is possible there’s something sticking inside the ammeter – but I doubt it.

That leaves only a problem in the dynamo or the regulator – or the wiring between the two and/or from the regulator to the ammeter.

My ammeter always reads zero – I have bypassed it as I have an alternator which would probably overload it.

On a different car (my ’59 Chrysler) I found that a wire was completely missing that meant the battery could not charge. The wiring was done a bit differently but effectively it was the equivalent of the wire between the regulator and the ammeter. I had owned the car for 11 years before I realized this – I attributed the occasional flat batteries to short journeys and an old battery. I fitted a brand new big battery before driving it to Sweden – we got as far as Bremen (about 500 miles) before it would not start after a fuel stop. When the ADAC man got us going it was dark and I could see the headlights did not get brighter when I revved the engine. They just go dimmer as we drove along. A bit of buzzing out the circuit showed no connection – because there was no wire!

I have no idea if that helps

Chris