Lotus Elan

Alternator wiring / Solenoid question

PostPost by: nwbaxter66 » Tue Sep 10, 2019 3:36 am

Original Dynamo car, converted to alternator using the RD alternator conversion kit and instructions.
While the alternator appears to be generating power, it isn't getting to the battery.
I have not got around to replacing the ammeter with a voltmeter.

I have not started digging around behind the dash yet, as I am afraid of what I am going to find there, but am trying to see if I can work out what might be going wrong.

When I remove the brown wire that allegedly comes from the ammeter, the engine stops. Should that happen?

Without that cable attached to the starter solenoid the car will not start, fuel pump will also not start.

What I think is happening is that there is a break in the wiring between the alternator and the ammeter, most probably between the regulator box and the gauge.

Would this make sense? Is there another way to check safely?

Thanks for the advice.
Nick Baxter
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1969 Plus 2 (UK) - sold
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PostPost by: MarkDa » Tue Sep 10, 2019 9:47 am

If your dynamo was working before your change then you shouldn't have to rummage behind the dash as the conversion uses the original battery connections - albeit bypassing the regulator.
You say you think the alternator is working - have you checked the output voltage?
Should be 14v or so.
I suspect that disconnecting the ammeter breaks all the the low current circuits so yes it will stop the engine.
You could test this by turning on the lights and seeing what happens.
I've a sneaking suspicion that the alternator exciter wire isn't working.

Useful thread here
viewtopic.php?f=38&t=36823&start=
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PostPost by: nwbaxter66 » Tue Sep 10, 2019 11:21 am

I think you are correct - the battery light has never actually worked and probably did not need to work for the dynamo to work
... now I need to get to that connection in the dash !
Thanks
N
Nick Baxter
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1969 Plus 2 (UK) - sold
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PostPost by: MarkDa » Tue Sep 10, 2019 11:43 am

With an alternator an ammeter is not really needed and as you say a voltmeter is more appropriate. Its wiring might not even match your alternator output.
So the first instance I'd be inclined to eliminate the ammeter from the circuit and connect alternator directly.
You shouldn't need to do anything behind the dash for this?
Then when you have a charging alternator you can remove the ammeter and replace it with your voltmeter and appropriate wiring.
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PostPost by: nwbaxter66 » Tue Sep 10, 2019 12:25 pm

The comment about removing the ammeter circuit makes perfect sense. However, I believe that it requires the “exciter” fix previously noted. One piece of information that I had failed to note was the missing battery light function which leads me to believe the “exciter” issue is a good one.

My assumption is that I can test this by running the exciter wire through a bulb to any switched 12v circuit I can find in the engine bay and view the result? This would seem to mimic what I am seeing in my wiring diagram?

Thanks for the continued advice

N
Nick Baxter
1970 Plus 2S (Federal)
1969 Plus 2 (UK) - sold
nwbaxter66
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PostPost by: MarkDa » Tue Sep 10, 2019 12:48 pm

Yes if you run your test lead from exciter to earth it should light when you turn ignition on.
If you don't have one a cheap digital multimeter will be a good investment as you will be able to check continuity as well as voltages.
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PostPost by: nwbaxter66 » Tue Sep 10, 2019 1:06 pm

Mark - have the multimeter and will try that at lunch time ... got to drive the car to work today (:
Nick
Nick Baxter
1970 Plus 2S (Federal)
1969 Plus 2 (UK) - sold
nwbaxter66
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Posts: 74
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PostPost by: nwbaxter66 » Wed Sep 11, 2019 12:27 am

Earthing the "exciter" cable didn't do anything.
Pulled the tach from the dash and surprise surprise - no bulb in the battery warning light.
Actually it appeared that half of the bulbs were in the wrong sockets!
Replaced bulb in battery warning light socket, put socket back in the "Correct" slot in the tach and lo and behold we have charging! ... and a beam/low beam headlight light.

I am now replacing bulbs all over the place and all sorts of things are working - being able to see gauges at night time is a great experience!

Thanks for the guidance.
N
Nick Baxter
1970 Plus 2S (Federal)
1969 Plus 2 (UK) - sold
nwbaxter66
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Posts: 74
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PostPost by: MarkDa » Wed Sep 11, 2019 1:08 am

Excellent
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