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Ignition Light

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R6MGS

R6MGS

Yoda
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The ignition light on the MGB LE periodically comes on if left it idle for a while...When we first got it the ignition light was almost always on, replaced the alternator with a NOS we had in the garage....this solved the problem....but now it comes on only after idleing for a while...it's probably the alternator again but is there anything else that could be causing this we could check before replacing the alternator?

Thxs
Zack
 
Indeed it is most likely the Alternator again but -

Measure the voltage at the battery and at the Alternator. If you are idling you shouldn't see much more than a half a volt difference (~0.5v). If it is more than that, then one or more of the wires/connections between them might need to be cleaned or replaced.

The easy thing to do first is check & clean the connections between the Alternator, Starter Solenoid all the way back to the Battery. If that looks good use a milt-meter (volt/ohm-meter) and measure the resistance and/or the voltage between those locations.

Good luck,
 
[ QUOTE ]
The easy thing to do first is check & clean the connections between the Alternator, Starter Solenoid all the way back to the Battery. If that looks good use a milt-meter (volt/ohm-meter) and measure the resistance and/or the voltage between those locations.


[/ QUOTE ]

Correct; the ignition light only glows when there is a voltage differential between the battery and the charging circuit. The differential can be due to either a bad alternator, a bad battery, corroded connections or a combination thereof.

First thing to do is clean ALL of the connections: battery cables, posts, ground cable where it connects to the chassis, the alternator lug at the solenoid, etc.

Are you sure the battery is holding a charge? If you have +14.5v at the alternator, but only 12 or so at the battery, I'd suspect a shorted battery cell or high resistance at the connections/cable. The opposite suggests the alternator.

Does the light dissapear when you rev the engine?
 
/ubbthreads/images/graemlins/iagree.gif With all the above comments,but isn't it just possible that the idle speed is too low?---Keoke
 
It idles nicely at 10.rpm Yes it does disappear when I rev it up.....the battery is good(almost new) and so are the battery cables(Clean)....I'll check the ground straps on the weekend(cars stored at different loaction).......thanks for all the suggestions!

Zack
 
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