Lurch has electrical issues

[heinkeljb]

Sorry this is a VERY long post, but maybe it will help others who face similar issues.

Lurch has been getting harder and harder to start. Typical of Dynastart issues. As I haven't done the brushes for a while and as my volt meter shows 12.** volts, I assumed that the issue was either the Starter relay or the Dynastart. As I had a spare set of brushes I decided to change them. Taking the dynastart out is not really a dificult.Undo all the cables going to it, making sure you know which cables are which. Df & D+, 30 and earth. Then undoing the strap clamp over the top of the fan. Don't forget to loosen the bolt at the bottom of the strap so that the strap can move otherwise you are going to bends the metal of the strap which if done too many times will cause metal fatigue in it, leading to possible failure which would not be good.

Took the brushes cover off, there appeared to be some life left in the brushes, but one of the brushes had a really thin braided cable compared to the others, so decided to change them. You have to undo the screws on the ends of the cables to be able to get the brushes out unless your brushes came with long enough cables. Once the brushes were out, the commutator looked a bit "blueish" which, is indicative of it getting hot. Not surprising considering the hard starting that was occuring prior to taking the Dynastart off.

Undo the 4 screws holding the end plate on and slowly force the end plate off, there is a bearing in the end cap which might make getting the end cap off difficult. Easier way is to tap the pulley end of the shaft and that will push the commutator through the Dyanastart body. Once all apart you can use a strip of fine sandpaper to "shine" up the commutator segments - unless there is a deep ridge caused by the brushes in which case it might be a question of getting it put on a lathe to skim it down to a smooth surface. Then use a broken piece of hacksaw blade with the "wave" in the teeth ground off so it is just the thickness of the hacksaw blade metal, i.e. less than a mm so you can use it to undercut the insulation between the commutator segments.

Anyway, I digress!

Sorted out new brushes and put the Dyanastart back together, tuned the shaft, no horrible noises so back on the engine, wired up. Let's start the engine! Nothing!!!

Recheck all the cable connections, still nothing. Maybe the issue was with the Starter relay after all? Get a Jump lead and bypass the Starter relay. Still Nothing!

Took the Dynastart off again. Took the brushes cover off again to check that the bushes springs were in the correct places on the brushes and that they were all the way in the brush holders. Tried using jump leads from a spare 12 volt battery, negative to the body of the Dynastart and then the positive cable from the battery touched briefly on terminal 30 of the dynastart. NOTHING! What is going on here?

Took the brushes out again and looked at the ends that should touch the commutator. These should have been showing some scrathes following the turning of the shaft whilst putting things together. They were only showing very light scartches, so I took a piece of fine sand paper and rubbed the ends of the brushes - ah! now they are shiney. There is a protective covering on new brushes to stop the copper content from tarnishing. I had forgotten to take that off.

Dyanstart spins when power is applied as explained above.

Put everything back together on the engine. Tried starting - NOTHING! What on earth is going on?

Used the spare battery to connect directly to the Dynastart, It Spins.... engine starts. This now points to the startere relay being faulty. So bypass it. Nothing. What? AH HA!! Bad battery! Checked the battery using my drop test unit. Has 12 volts with no load, but under load down to 4 volts.

So the whole hard starting was down to a bad battery? NOPE. Having put the spare battery which can turn the Dynastart over, engine now starts, but charging light does not go out.

Check the output fuse from the regulator - good.

To check the output of the Dyanstart follow this guide:-

Bosch and other Continental dynamos/Dynastarters

Disconnect the wires D+ and DF. Connect the DF terminal to earth (DE). Connect a headlamp bulb across D+ and earth (DE) and run the engine. If the dynamo is good the bulb will light. Raise the revs and the bulb should burn brightly and may even blow. Don't do this for too long as the dynamo is running unregulated.

So it appears that my electronic regulator has died. I'll put a mechanical one on today as I have it spare "just in case". I post the results later.

John

[ogdenenterprise]

The process of elimination to find faults is very time consuming
and a lot of head scratching as well. But doesnt it feel good when you have
finally found the problem, hopefully you have.

Dave

[heinkeljb]

I have put the mechanical regulator on and can confirm that the charging light now goes out as the revs rise. the charging light flickers at idle, but goes out as the revs rise. So some how I have managed to "kill" my electronic voltage regulator.
Unfortunately as the electronics are "potted", it is unlikely I will be able to repair it so will probably have to buy a new one. Still while it worked, it provided a more stable output than the mechanical one.

John