Charging lamp problem.

[Juel72]

I am still working on sorting out the electrics on my 1969 AC Sport coupe.

The engine has not been started yet (after total rebuild). So I do not know if the charging system are working.

The alternator is new and so is the battery.

The problem is that the charging indicator lamp does not come on when I turn the key to the ON position.
I have checked the bulb and it is OK. The relay is working also. But I can not hear it clicking when I turn on the ignition.

If I measure the voltage on the spade connector on the alternator is says 0,5 volt. But at some time today I measured app. 12V.

I have a ground strap on the bell housing to the frame of the car.

Please point me in the right direction to sort this issue out.

Thanks

[Flatspyder]

Depending on your setup. Normally, with the stock alternator, The indicator light goes on but then should go off when you rev your car over 3000 rpm.

If the light does not even go on, it means the alternator is charging as soon as the car is turn on.. Get a volt meter to verify.

This happens a lot and it just means you have a different kind of alternator than stock.

Hope that helps.

[Juel72]

Thank you for your reply,

The engine has not been started yet. So I can not verify whether it is charging or not.

But I would like to know how to check the system.

The relay is checked, it is closing OK. The alternator is new and it does not seem to have a built in voltage regulator.
The voltage regulator is the original version fitted on the inner wing in the drivers side.

Voltage at the bulb is 0,5 V.

Why?

[aj81spider]

You will need a wiring diagram for your car and will need to trace the wires in both directions from the lamp. It sounds like you have a bad connection somewhere.

Going from memory I believe on my car the lamp always has 12 V and is grounded through the relay (although it may be the other way around and powered through the relay). When the alternator starts the relay gets opened and the circuit is broken so the light goes off. If you have 0.5 volts it could be because of poor connections in the wires to the light, or it could be because the connection to the relay is bad.

It's hard to diagnose without a wiring diagram (and I don't have one for the coupe), but pretty simple once you know where the wires are connected.

[Juel72]

Hi again,

I have through the connections. They are now ok.

But still 0,5 v on the spade connector wich feed the yellow/orange wire. The wire that goes from the alternator to the relay.

I have tried to connect the same wire directly to the battery. Then the relay clicked and the charging bulb was lid.

What can cause only 0,5 volt on the spade connector on the alternator.

There is full battery voltage on the black wire that goes on the 6mm stud on the alternator.

Someone, please come with your suggestions.

[azruss]

early spiders have an external voltage regulator. should be the large box on the drivers side inner fender. this regulates voltage through a pair of spring loaded contacts. you could easily have a set of burnt points under the cover. In severe cases, the points can weld shut and you get no charging from the alternator.

[Juel72]

I do have the voltage regulator on the driver side inner wing. It could be the problem source.

But does it have something to do with the small yellow/orange wire comming from the alternator and going to the relay?

btw: the wiring diagram is the same as for the early spiders.

[azruss]

cant tell you about the wiring color. It is easy enough to pop the top off the regulator and look at the condition of the points.

[Juel72]

I wiill check the voltage regulator.

I am not an educated mechanic or electrician,

But I would like to know where the voltage on the alternator spade connector should come from.
From the big black wire directly connected to the battery, or from the gray wire that goes from the voltage regulator to the alternator.

Remember the engine is not started yet. It is the voltage to close the relay to the charge indicator lamp I am missing

[Juel72]

Hi again,

I was thinking about the relay for the charge lamp.

When I checked the relay I noticed it is a normally open relay.
It this correct?

[aj81spider]

Here's how the wiring works on my 1974 Spider:

A yellow wire goes from the alternator to the relay. The relay is normally closed. There is 12 volts from a switched fuse going to the light. A black/violet wire goes from the light to the relay, and the other side of the relay is grounded. When power is on and the alternator is off the light will be on because the normally closed relay connects the light to ground. When the alternator starts running the yellow wire from the alternator opens the relay.

There is also a gray wire from the alternator to the voltage regulator, and an orange wire from the fuse box with switched power to the voltage regulator.

Hopefully that helps.

[Juel72]

Thank you for alle the replies.

I have found the reason for my charging lamp not working.

The new and shiny relay mounted by the guy that build the car up from at pile of rust, is not correct.

The relay in the car is a normally open. So the charge indicator lamp is acting in the oposite way.

So, I will source a normally closed relay and get back to the garage.

A car this nice need to come back on the road

[vdesigner99]

In regards to the charging lamp, does anybody know if I change the incandescent lamp to an LED, would this disrupt the alternator circuit? I am about to change the instrument light to LED and have seen post that the charge lamp is in circuit with the alternator.

Thanks!