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One for the Wiring Wizards...

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One for the Wiring Wizards...
#1
Captain Ron Avatar
Captain Ron Franklin Green
Lodi, WI, USA   USA
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1965 MG MGB "Happy Jack"
'65 converted to 12V negative ground. Battery is on a switch courtesy of the PO. When battery is turned on, red ignition warning light comes on. When ignition is switched to "on" position, light goes out whether engine is running or not. Shouldn't the warning light be on if engine is not started? I think I'm one wire away from the way it should be, and I don't think the alternator can charge in this configuration. Tried reading schematics, don't know what the hell I'm looking at. Is there a certain color wire I need to move?

Any help is truly appreciated!

fg

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Re: One for the Wiring Wizards...
#2
ozieagle Avatar
ozieagle Gold Member Herb Adler
Geelong Victoria, Australia   AUS
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1958 Wolseley 1500 "Wooly"
1966 MG MGB "Bl**dy B"
1995 Toyota Highlander "Hi Ace Van"
2022 MG ZS
I would check the wiring to the cutoff switch. There must be another path around this switch for the light to get any juice.

Herb


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Re: One for the Wiring Wizards...
#3
Captain Ron Avatar
Captain Ron Franklin Green
Lodi, WI, USA   USA
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1965 MG MGB "Happy Jack"
In reply to # 3456280 by ozieagle I would check the wiring to the cutoff switch. There must be another path around this switch for the light to get any juice.

Herb

Where might I find a cutoff switch? Is there a wire color I need to address?

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Re: One for the Wiring Wizards...
#4
ozieagle Avatar
ozieagle Gold Member Herb Adler
Geelong Victoria, Australia   AUS
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1958 Wolseley 1500 "Wooly"
1966 MG MGB "Bl**dy B"
1995 Toyota Highlander "Hi Ace Van"
2022 MG ZS
In reply to # 3456272 by Captain Ron Battery is on a switch courtesy of the PO.

This is the cutoff switch.

Herb


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Re: One for the Wiring Wizards...
#5
Cruisedon66 Avatar
Cruisedon66 Pete W
St. Louis, MO, USA   USA
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1976 MG MGB
Check these steps and see if the PO missed anything.

http://www.mgexp.com/article/neg-convert.html


http://www.mossmotors.com/graphics/products/PDF/130-078.pdf Moss Motors

John Twist

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Re: One for the Wiring Wizards...
#6
bencii Silver Member Ben Colpitts
Eden Prairie, MN, USA   USA
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1966 MG MGB
1973 MG MGB
Sounds to me like the PO set it up to warn you if you remove the key and leave the battery switch on. The battery switch has a key which is removable correct?? If you want it to operate like it normally would without the cutoff switch you will need to move the wire from the battery switch over to the next terminal on the ignition switch if that is how it was wired up. Since it is aftermarket it will not be in any of the wiring diagrams and you will need to tell us how the battery switch is wired. pictures always help. Are you able to trace the wires from the battery switch?

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Re: One for the Wiring Wizards...
#7
Captain Ron Avatar
Captain Ron Franklin Green
Lodi, WI, USA   USA
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1965 MG MGB "Happy Jack"
The battery switch does not connect to the ignition switch. I am told that this light is part of the charging circuit and therefore necessarily wired correctly. I cannot test my alternator if this is true.

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Re: One for the Wiring Wizards...
#8
arnolda Avatar
arnolda Arnold Adams
Vancouver, WA, USA   USA
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1980 MG MGB Limited Edition (LE)
Looking at the Advanced Auto diagrams for cars with an alternator, you should have a white wire from your ignition switch to the indicator light and a brown with yellow tracer wire from the light to the IND terminal on your alternator.

ps. the brown/yellow wire previously went from the light to a regulator when the car had a generator

The Advanced diagram for a 65 B shows three white wires connected to the ignition switch. The second wire connects through a multi bullet connector to the tachometer and on to the coil, to the fuel pump and to a fuse feeding the green wire circuits. The third wire also connects to the tachometer ( probably to power the tach).

Keep at it. It will come.

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Re: One for the Wiring Wizards...
#9
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B-racer Jeff Schlemmer
Shakopee, MN, USA   USA
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1950 Willys Jeep Pickup "Ratrod"
1964 Land Rover Series IIA
1971 MG MGB
It sounds like the charging indicator light is wired to the "accessory" position at the key rather than "run." My guess is that this will be an easy wire swap under the dash, once you find it. Does the charging system work? Measure voltage before/after starting to verify.


jeff@advanceddistributors.com

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Re: One for the Wiring Wizards...
#10
Captain Ron Avatar
Captain Ron Franklin Green
Lodi, WI, USA   USA
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1965 MG MGB "Happy Jack"
In reply to # 3456728 by B-racer It sounds like the charging indicator light is wired to the "accessory" position at the key rather than "run." My guess is that this will be an easy wire swap under the dash, once you find it. Does the charging system work? Measure voltage before/after starting to verify.

I just installed a new ignition switch. Followed the directions and wire color references carefully. Previous switch did not have "accessory" position; I wired it straight to the radio on the new switch. My biggest concern is that the alternator might not charge the battery because the warning light is part of the charging circuit. Still trying to figure this one out. Is the current going in the wrong direction? As currently wired, the current goes FROM the battery to the light, I believe it's supposed to run TO the battery from the alternator.

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Re: One for the Wiring Wizards...
#11
tvrgeek Silver Member Scott S
Hillsborough, North Carolinia, USA   USA
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1973 Triumph Stag
Simple. Not running, 12.4 V or so. Running, rev over 1200 RPM, you should have 14.2 V. If not, you are not charging.

It does sound like someone re-wired incorrectly. Use the Advance schematics to verify. It is very simple. Trace one wire at a time. Don't let the entire page confuse you.

You are correct, the ignition warning light is mandatory for the alternator to start charging.


Cogito ergo sum periculoso

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Re: One for the Wiring Wizards...
#12
Wray Avatar
Wray Gold Member Wray Lemke
., SC, USA   USA
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1956 MG MGA
1958 MG Magnette ZB Varitone
1973 MG MGB
1974 MG MGB GT    & more
In reply to # 3456804 by Captain Ron
In reply to # 3456728 by B-racer It sounds like the charging indicator light is wired to the "accessory" position at the key rather than "run." My guess is that this will be an easy wire swap under the dash, once you find it. Does the charging system work? Measure voltage before/after starting to verify.

I just installed a new ignition switch. Followed the directions and wire color references carefully. Previous switch did not have "accessory" position; I wired it straight to the radio on the new switch. My biggest concern is that the alternator might not charge the battery because the warning light is part of the charging circuit. Still trying to figure this one out. Is the current going in the wrong direction? As currently wired, the current goes FROM the battery to the light, I believe it's supposed to run TO the battery from the alternator.

It doesn't work like that. When you first switch the ignition on the white from the ignition switch applies 12vdc to the alternator field circuit via the bulb. Since the alternator is not putting out voltage the difference between the ignition voltage and the alternator (essentially ground) makes the bulb light. When the car runs the alternator spins up, the field excites, and the alternator starts putting out voltage. Now the alternator and the ignition are at the same voltage and the light goes out.

Why did you wire it "straight to the radio"? Maybe you could elaborate on that.

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Re: One for the Wiring Wizards...
#13
Captain Ron Avatar
Captain Ron Franklin Green
Lodi, WI, USA   USA
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1965 MG MGB "Happy Jack"
The accessory position is for the radio, etc, per the switch instructions. The remaining 3 terminals are wired the same as the previous (no accessory position) switch. The PO also installed an on-board battery charger and removed the bulb from the warning light. When I replaced the bulb I discovered the discrepancy. According to the voltage specs posted above and my voltmeter, we ain't chargin' no battery. I believe that he charger, missing bulb and battery switch were intended to cover up the wiring problem.

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Re: One for the Wiring Wizards...
#14
Wray Avatar
Wray Gold Member Wray Lemke
., SC, USA   USA
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1956 MG MGA
1958 MG Magnette ZB Varitone
1973 MG MGB
1974 MG MGB GT    & more
I gotcha. Well, something ain't right. A white from the ignition "on" should connect to the Brown/Yel that goes to the bulb then to the alternator. You'll probably have to check each of the terminals to see which ones are actually hot when the ignition is on.

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Re: One for the Wiring Wizards...
#15
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B-racer Jeff Schlemmer
Shakopee, MN, USA   USA
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1950 Willys Jeep Pickup "Ratrod"
1964 Land Rover Series IIA
1971 MG MGB
Even my tractor has an accessory position. I'd bet your new switch does too, and its part of the problem.


jeff@advanceddistributors.com

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