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MG Midget and Sprite Technical - Lights on without fuse

Question: My lights and flashers come on when I have everything disconnected from the fuse box & 2 in line fuse holders. Is that normal?

I found this when trying to fix a major short that occurs whenever I turn the ignition key to the start position. There's a click and everything dies. If I disconnect the battery and then reconnect it I have power to everything until I turn the ignition key again.

I don't know if the two things are related or not.

If I leave the battery hooked up and there is a constant draw on it, it goes dead in a few days. Should the headlight switch be drawing power all the time?

When I look at the schematics it appears that the brown wire goes directly from the light switch to the starter solenoid, which then goes directly to the battery. If I disconnect that brown wire I have no power to the headlights.

Any thoughts or suggestions would be really helpful.

Thanks

Thor Patterson-Ritz

export models may be different but IIRC the sidelights and flashers are not fused but perm live so in a night-time emergency the warning lights still work.
David Smith

Export models do not fuse the headlights, but the marker lights are fused (the two fuses closest to the front of the car with the red wires attached).

Thor,
Try disconnecting the alternator and see if the drain disappears. Actually, the drain is probably fairly small, so you should be able to disconnect the power lead from the battery, insert an ammeter in series between battery and battery cable, and start disconnecting things until you find the culprit. I am suggesting that it could well be the regulator in the alternator.
David "no charge" Lieb
David Lieb

"There's a click and everything dies."

Could it be as simple as unclean terminals, possibly in conjunction with a weak/failing battery?

The headlamp switch shouldn't draw power all the time, but that doesn't it or something else isn't...

Check/charge/replace your battery and keep the negative terminal off when not driving until you track down the problem?

What David said too.
Richard 1979 1500

Boot light staying on? That will drain a battery and is often overlooked.
Clive Reddin

lets cut to the real question....how old is the battry, and did you celebrate the 4th of july with wiring work in your car...aka.. make a sparky....

if so dead cell in battry, but could be dirty/loose terminals on the batt. as richard points out.

take the battry to a shop and have checked...sometimes they dont show up as bad with limited home test equipment

prop
Prop

Sounds like a bad short in the starter. Probably the fields grounding on the case.
Tom

I replaced the battery 3 months ago and it holds a charge if totally left disconnected. Since I have disconnect almost everything it doesn't seem to have the constant drain now. So I need to slowly add things back and see when it reoccurs.

The short is so weird. It's there and then gone. Could the starter solenoid be bad? Work one moment and then not the next? Then again I think it may not be that either as I have the following symptoms:
1. When I turn on the dash lights using the light toggle switch all the dash lights come on but if I turn them off using the switch and then turn the ignition key to the accessory position all the dashboard lights come on, even though light switch is off.

Now if I turn the ignition key to start I get the click and everything dies until I take the battery cable off the battery. So there has to be some feedback or something. I just can't figure where. The dash lights have "Red/White" and Light toggle switch has "Red/Green".

Thor Patterson-Ritz

Thor:

I see you are becoming a familiar of Lucas, Prince of Darkness...

"When I turn on the dash lights using the light toggle switch all the dash lights come on"

I assume you mean the usual lights, i.e. only those gauges and switches that SHOULD come on.

" turn the ignition key to the accessory position all the dashboard lights come on"

I don't have wiring diagrams for the Pre-Rubber Bumper cars and I don't know the vintage of your car, but 1975-1979 have only one item energized by the accessory circut, the radio. One wire.
How or where those two circuts might come in contact is a mystery, but...

The accessory position is your decent clue, I would remove the radio console and see if anything fishy is going on with the unfused, white/green wire feeding the radio.

A grosser, quicker and more thorough (as in eliminating the entire accessory circut all at once) option would be to snip the white/green wire right off at the ignition switch junction block under the steering column (Oh, was that the sound of some future owner cursing the DPO?). See if this eliminates the dash lights coming on in the accessory position.

"Now if I turn the ignition key to start I get the click and everything dies until I take the battery cable off the battery"

I'll bet you a cup of coffee you have two unrelated problems going on and it's driving you nuts trying to think of them as one.

"I replaced the battery 3 months ago and it holds a charge if totally left disconnected"

Could still be battery. Or loose terminals. Or the battery. Or loose terminals.

"If I leave the battery hooked up and there is a constant draw on it, it goes dead in a few days"

That will knacker a "new" battery quite nicely after a few cycles.

Or as tom points out, could be a starter failure? Or solinoid?

By the way, as to your first post at the top, while replacing my failed headlamp switch recently I placed an inline fuse (25 amp) between the brown wire and the switch.

Just to mess with the future owner.
Richard 1979 1500

This thread was discussed between 08/09/2008 and 12/09/2008

MG Midget and Sprite Technical index

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