dynamo testing ?

[mattyb]

dynamo tested off the car - spins very fast when a battery is connected to the D terminal but slower when both D & F terminals are bridged together - brushes are excellent as is the commutator. Continuity tested on the D and F wires from the dynamo to the regulator ( thick yellow for D and yellow/green for field ) and this is also good - fan belt in good condition and not loose

On the car if you bridge the D & F terminals at the back of the dynamo everything works perfectly - 13.2 up to 14.1 ish at the battery - gen light goes out - points cut in on the regulator - if the bridge wire is removed at the back of the dynamo the dynamo wont charge - gen light comes on - battery starts to drop to 12.7 ish - have tried 3 regulators and 2 dynamos and the readings are the same

Any ideas why it only charges when there is a bridge wire between the D & F terminals on the back of the dynamo ?

cheers

Matt

[bmcecosse]

You are forcing it to charge flat out when you do that - I had a switch to do just that on my Rally Minor when running on 'sections' with extra lights etc on - to get max brightness. So - there MUST be a problem with the Regs or the wiring if it doesn't charge without the bridge. What does the red light do ?

[mattyb]

Evening BMC

red light (with the bridge wire in place ) comes on when you switch on the ignition, goes off when engine started - the regulator points flip over when you first rev the engine up and then stays over - wiring is in good condition - very good condition - as I mentioned, have tried 3 regulators ( but not to say there all faulty !)

[bmcecosse]

But what does the red light do when there is no bridge ? If nothing - I guess you have to try adjusting one of the Regs till it does click in !

[Trickydicky]

Here's a link to download the Lucas Fault Diagnosis Manual. It explains how to test the Dynamo and Control Box.
It's useful to have to hand
http://www.gt40s.com/images/howto/LynnM ... Manual.pdf

[mattyb]

Roy and Richard

many thanks for the advice and links - regulator adjusted and car now charging !

I used this link http://www.justbrits.com/Articles/Lucas05.pdf

[bmcecosse]

Well done !