Can any dynamo / electrics experts diagnose this?

[bstark]

Steffan said:

In view of all the work the OP has done it does seem probable that either the Dynamo is failing or the control box is failing. I appreciate the control box is new and the Dynamo declared good but something is causing the fault to continue. I would be doubtful of those two items the OP seems to have covered the poor contacts probabilities. Best of luck to th OP electrics are always tricky on older cars.

That's my view too... And thanks!

[kev b]

Have you had a look inside the control box? I suspect the fault is in there.

You mentioned not being able to run a wire from the dynamo to the battery, you can use the live cable on the starter as that is the same as the battery live, in effect. In fact that is probably where the charging cable goes when it leaves the control box.

[Steve_D]

bstark said:

Have just checked regulator earth - fine, all the wiring between regulator and dynamo - fine, and all the fuses - fine...

So where does the live feed from the reg. go too?

All the wiring including the battery connections need to be cleaned.

Steve

[bstark]

The live output just disappears into the loom and I have to admit it didn't occur to me that the starter is where it may end up. I'll check that. The starter is only a year and a half old though so it wasn't that long ago the contacts at that end were removed and cleaned. Could be the join with the connector though.

I have also managed to source some new dynamo brush springs from Europe, and some NOS brushes in case the brushes are floating at high revs. Just waiting on the post...

[bstark]

Well, the output to the starter motor checks out as well so back to the dynamo...

[Steffan]

bstark said:

Well, the output to the starter motor checks out as well so back to the dynamo...

Could be two things IMO. The Dynamo must be the most probable one but the new control box may be the culprit. Have you got access to a decent meter which could read the actual output of the Dynamo at the Dynamo itself and then through the control box with the engine running at a fair rate of revs and finally the battery itself both on and off charge which should be showing charge when the Dynamo is running? You might need an extra pair of ands to effect this but testing the car in this way coud pinpoint where the problem seems to be. It is obviously an oddity because having replaced the control box and checked out the Dynamo you would expect the culprit to be apparent. Testing with a meter is a lot less work than removing components for testing. I would suspect the Dynamo but I await the confirmation when you have checked these out again. Best of luck in you considerable efforts.

[bstark]

This is maddening!

Stripped the dynamo and the springs and brushed indeed look fine. Fitted the new set of both just in case, and also cleaned up the brush runners as one of them was full of slight surface rust.

Put the dynamo back together, checked it motored ok (it did) and reinstalled in car.

Exactly the same symptoms, only now the light stays on once the increase in revs has set it off, even if you then back down to idle. It did exactly this the last time the dynamo was stripped by the specialist.

So, individually everything checks out to the level I can apply.

Auto electrician here we come, if I can find one who gets these...

[kev b]

Contacts are sticking in the control box?

[Steffan]

kev b said:

Contacts are sticking in the control box?

I do wonder about the control box. With aged spares success is not always guaranteed. Auto electrician with meter must be the probable best route. At least the OP knows all the connections are sound. Just got to stick at it. Best of luck to the OP.

[bstark]

Cheers guys. It's being looked at next week.

Sticking control box sounds perfectly reasonable, but identical (and I mean identical) symptoms with two separate boxes? Hopefully a specialist will just roll his eyes, say 'this is yer problem' and it will be a long time before I have to pull the blimmin' dynamo again! :-)

[radical78]

when fitting a new reg box you somtimes had to set them to the dynamo output by adjusting a screw which adjusted when the points opened and closed but its a long time ago strugling to remember exactly how/wat to set it to

[pf3]

Hi have you fixed the charge light problem? was it still charging when the light was on.

[bstark]

In theory it has finally been fixed, having resorted to an alternator conversion following multiple attempts with auto electricians, dynamo repairs, replacement dynamo, 3 different regulators including a solid state one...

I should know for sure later this week when I get the car back...

[Steffan]

bstark said:

In theory it has finally been fixed, having resorted to an alternator conversion following multiple attempts with auto electricians, dynamo repairs, replacement dynamo, 3 different regulators including a solid state one...

I should know for sure later this week when I get the car back...

That is a pretty comprehensive repair! Insulated as we are with modern motoring reliability it is easy to forget that only a few decades ago motoring was much more breakdown prone. Probably why my latest Green Flag quotation for all risks uk mitring cover is dwn to £30 odd!

I would expect the repair to be a complete success. It damned well should be. Dynamos were always under pressure in bygone years. The alternator conversion should eradicate this problem permanently. Alternators are massively more efficient generators of electricity. All cars need electricity to function and as you have discovered getting effective repairs to obsolete dynamos ad associated CVC boxes can be a long drawn out business. I would expect this comprehensive repair to be totally effective. Best of luck to you and enjoy driving your classic!

[bstark]

You have no idea how much I hope you are right Steffan!