Ammeter Wiring

[Wombat]

The important thing to remember is that all power connections to lights etc should be on the Alternator (or generator) side of the ammeter if you want the ammeter to show what is going into or coming from the battery. Tom H clearly describes how the ammeter should work is wired as Rootes intended.

Ed, in your case, I am almost certain the lights are connected to the battery side of the ammeter, so with the engine stopped and the lights on, the current comes straight from the battery and does not go through the ammeter. With the engine running the current for the lights comes from the alternator, through the ammeter and registers as charging although the lights take most of it before it gets to the battery. I wired up a car so it behaved the same way, then realised the ammeter wasn't telling me what I wanted it to, so changed the wiring.

 

[ozzie alpine]

Hi Tom,

..... If every diagram I look at is the same, obviously Rootes stuffed up too .

Regards, Robin.

Surely not !!!
(but has anyone noticed the error in the Alpine SII wiring diagram in the workshop manual? - the overdrive switch feed, ie white/ignition, mysteriously turns into a brown/battery feed at the fuse box...had me confused for a while).

 

[Nickodell]

Tom H: Great description! The only quibble I would have is that even with a "fully charged" battery, the ammeter should show a slight (1 or 2 amps) charge, not a zero. Of course, after runing for a substantial time, if the ammeter continues to show a large charge, either it's wired incorrectly (as detailed in earlier posts) or the battery is duff. Otherwise, a very lucid description.

 

[burgy711]

This is all great stuff and I love the detail. But, what I really want to know is what does it all mean when the ammeter is working fine UNTIL you turn the head lights on and the ammeter goes dead. ...... PRINCE OF DARKNESS........ again......

 

[Tom H]

Robin,

Great post to show the diagram. That's the diagram I use, but I have no scanner to get it posted. I should have linked the on-line WSM page but did not think of it. Just for extra I am putting the link here to see how well it works:
http://www.rootes1725cc.info/wsm145/wsm_n/n_26.htm

Nick, Sorry I mis-quoted you! It really drives me crazy how often I get names crossed about who said what about what when posting. The only satisfaction I get is that the problem is so common! Glad you liked my description and I agree with your comment about a few amps even when charged.

Burgy, Do you really mean the ammeter goes dead? I have never had an ammeter go bad. But maybe you mean the ammeter goes way NEG indicating something in the Lucas charging system went dead. That's something we all see.

Tom

 

[Nickodell]

Tom: No sweat, we've all done it!

I only had one ammeter go bad, and that was in my 1947 Allard K1. A spider could be seen frequently crossing the dial. As it showed up for months I could only conclude that it lived on volts and amps, but, inevitably, one day the needle stuck. I concluded that spider man had spun a web in the works, although what prey he hoped to attract was a mystery. I never bothered to take the meter out, as that was the least of the troubles with what my wife called The Monster. (All right, all right, you dirty-minded lot: I'm speaking about the car )

 

[64beam]

Hi Tom,

The charging diagram makes it much clearer than the full diagram especially when it's only in black and white. It was a great post and even with my electrical background, I learnt a bit as well (never too old to learn something).

Regards, Robin.