Overcharging?

Post by **dawpooldad** » Tue Oct 10, 2006 8:42 pm

Hi, I run a '54 splitscreen SER II with 803cc original engine.
Just recently, I noticed that my ammeter was showing a charge rate of over 30 amps as I was driving normally! Everything else seems to be OK but the guage goes off the dial when I rev up!

I've had the dynamo off and everything appears to be OK, so I changed the voltage regulator and it is still the same.
Now I suspect that the guage might be faulty as the car drives and appears to be working OK. I dont get any fizzing battery or brightness or blowing of lamps, so my question is:- Has anybody else had this problem or am I missing something?
Hope someone can help.
Regards
Dawpooldad

Post by **alex_holden** » Tue Oct 10, 2006 9:23 pm

What is the battery voltage when it does this? I doubt the ammeter is faulty so you need to figure out why the battery is taking a large charging current. Do you have another known-good battery you could try temporarily putting in place of the current one?

Post by **dawpooldad** » Wed Oct 11, 2006 8:48 pm

Hi, thanks for that.
I haven't as yet, checked the battery voltage and I will do so at the weekend. The battery is quite new and I have checked it with a hydrometer and not surprisingly, its showing fully charged.
I will also try putting another battery on as suggested.
Thanks again
Dawpooldad.
ps. I don't have a big hammer!!

Post by **bmcecosse** » Wed Oct 11, 2006 8:57 pm

Is the ammeter a recent installation - or has it 'always' been there ? 30 amp charge will make your battery fizz - maybe even explode!

Post by **alex_holden** » Wed Oct 11, 2006 9:12 pm

dawpooldad wrote:ps. I don't have a big hammer!!

Well, there's your problem. How can you possibly manage to work on old cars without a big hammer?

Post by **JimK** » Wed Oct 11, 2006 9:21 pm

Indeed. A large lump of something on a stick for "persuading" recalcitrant parts to do your bidding. I currently have the Mk3 large hitting stick: an 18" steel marquee peg.

To keep this vaguely on topic - the new car wouldn't start after a 10-mile trip with lights and wipers on. Turns out the belt was loose and not turning the alternator properly. Must get a spare belt...

Post by **alex_holden** » Wed Oct 11, 2006 9:43 pm

Did the ignition light not come on to warn you the alternator wasn't working?

Post by **JimK** » Wed Oct 11, 2006 9:47 pm

alex_holden wrote:Did the ignition light not come on to warn you the alternator wasn't working?

No, it was charging but not very well because the belt wasn;t tight enough to turn the alternator against the load - voltage at the battery terminals was about 12.6 with the engine running. When the belt was tightened it went up to 13.5V.

Post by **JimK** » Wed Oct 11, 2006 9:58 pm

alex_holden wrote:Did the ignition light not come on to warn you the alternator wasn't working?

No, it was charging but not very well because the belt wasn;t tight enough to turn the alternator against the load - voltage at the battery terminals was about 12.6 with the engine running. When the belt was tightened it went up to 13.5V.

Post by **alex_holden** » Wed Oct 11, 2006 10:37 pm

Good job, it can be tricky to figure out why a charging system is working but not well enough to charge the battery properly - it's easier to diagnose if it doesn't work at all

Post by **JimK** » Thu Oct 12, 2006 7:52 am

alex_holden wrote:Good job, it can be tricky to figure out why a charging system is working but not well enough to charge the battery properly - it's easier to diagnose if it doesn't work at all

It wasn't that hard once I noticed that the long belt run between the crank pulley and the alternator was flapping like a sail in a light wind

I had one years ago where half the rectifier had died so there was enough from the still-working half to keep the ignition light off but not enough to make up for running the headlights. That was a bugger to spot.

Post by **dawpooldad** » Fri Oct 20, 2006 11:55 pm

Hi guys,
thanks for all the help. The problem turned out to be the dynamo. I originally checked it with an avometer and it was pumping out the required volts, so as I said, I changed the voltage regulator( which also turned out to be faulty!

)
As you advised I checked the battery voltage which continued to rise with revs way past the required level.
So, I changed the dynamo, then the ignition light wouldn't go out

So I replaced the original regulator and everything worked

On dismantling the dynamo, I found that the solder on the comm had melted, so at some time it had overheated and discomnocterated itself

So once again, thanks.
Dawpooldad

Post by **bmcecosse** » Sat Oct 21, 2006 2:55 pm

So really - the problem was the 'new' regulator - which probably ruined the old dynamo by allowing it go far too high volts. Now you have a good dynamo and the original regulator - yes ? And it all works well ! You may now have a spate of failing bulbs since they will all have been strained by running at too high volts!