Checking the dynamo

Hi,

I've had some starting difficulties recently in that my car would lose charge overnight, or not charge up whilst I was driving. I am almost certain that the problem was the aging battery, but it's got me thinking about checking all other parts of the charging system to ascertain their condition.

My car retains the original 6 volt electrics, and the original dynamo (generator?). How can I check if this is putting out the correct power? I have a multimeter I can check it with.

Thanks in advance!

Reply to
Howard Rose
Loading thread data ...

I'd also like to add that it now has a new battery! A proper sized type 404, just like the original.

Reply to
Howard Rose

Do 2 tests:

1) Voltmeter across battery terminals. Should read 13.5 to 14.5V with engine revving. Try this with headlights on as well.

After first cranking the engine (battery somewhat discharged) the charging voltage should be 14.0V or above. If the charging voltage *never* goes above ~13.5V, the battery will get "soft" over time.

These ranges are approximations. Voltage regulators differ widely.

2) With everything shut off, remove battery Neg. cable. Connect multimeter (VOM) set to milliamp range from the cable end to the battery Neg. post. (Blk meter lead to battery post; Red meter lead to cable end.)

If the meter reads less than ~100 milliamp, there is no significant drain on the battery that would discharge it overnight.

Speedy Jim

formatting link

Reply to
Speedy Jim

On my Mini the regulater stuck closed sometimes -draining the battery overnight. Took me ages to find that one !

Rich

Reply to
Tricky

Much appreciated for your advice, but what figures am I looking at for a 6 volt car?

The 12 volt values are still appreciated, since I need to check my sisters Mini also (I assume the values are the same for a car with an alternator?).

Reply to
Howard Rose

Same for an alternator. but the regulator should be built in to the mini alternator.

Half Jims figures for 6v - easy as that !

Basicly the voltage should be higher with the engine reving than with it off !

Till you get it sorted you can try disconnecting the neg battery terminal overnight. If it still goes flat - its your battery.

Rich

Reply to
Tricky

So it really is as simple as that!!

I've put a new battery on the car, since the one on there was 4 or 5 years old. It seems to have worked so far. I just want to see if the rest of the charging system is up to scratch since it is coming up to winter now!

Thanks for the help!

Reply to
Howard Rose

Divide by 2 for 6V.

Yes, alternator values will be similar to dynamo although regulator action (programming) can be somewhat different.

BTW, I don't see any reference to Mini in the original post.

Jim

Reply to
Speedy Jim

Thanks, Jim! I'll have a look at it tomorrow.

It was something I added since I only just remembered about it! I'm going to check the Mini too.

Cheers :-)

Reply to
Howard Rose

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.