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70 ambassador 360 alt light on

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amboamx70 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amboamx70 Quote  Post ReplyReply Direct Link To This Post Topic: 70 ambassador 360 alt light on
    Posted: Sep/26/2022 at 3:26pm
my 70 ambassador recently developed a cond. where after starting the engine when warm , the alt. light will stay light until the engine r p m increases . after that it will stay off till the next restart . this doesnt happen when the engine is cold- regulator or alternator ?  how to test? i used to know tis stuff but have forgotten how.   old age creeping in
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nickleone Quote  Post ReplyReply Direct Link To This Post Posted: Sep/26/2022 at 7:02pm
Check with multi meter voltage output to battery when cold and when warm .
And voltage at battery with engine off.  Report results.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Sep/26/2022 at 11:50pm
Did you replace dah indicators eith LEDs lately? 

What changed recently?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sweatlock Quote  Post ReplyReply Direct Link To This Post Posted: Sep/27/2022 at 5:01am
Typically when the engine is started cold the choke is on and the RPM’s are higher than when the engine is warm. Which is the same thing that puts the light out when the engine is warm (accelerating and increasing the RPM’s). 

X2 on getting a multimeter and checking the voltage output. 


Edited by sweatlock - Sep/27/2022 at 1:05pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Sep/27/2022 at 10:15am
If the caps come off the battery, when was the last time you checked the electrolyte levels.
Do the voltage checks and post back, but don't run out and buy a new battery if your current one has low cell levels. Distilled water should be the only thing used to top up battery cells.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Goodtimes Quote  Post ReplyReply Direct Link To This Post Posted: Sep/27/2022 at 2:56pm
Agree with sweatlock, condition normal, alternator needs higher RPM to start charging
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bigbad69 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/27/2022 at 6:45pm
Alternators do have a stall speed i.e. they need to turn faster than a certain RPM before they start up. However, the ALT light on at idle is not normal. You should not have to spin up the alternator to make the light go out.

Was it always the case with this car, or did something change, as tomj asked?

If you were working on something when this problem started, that provides a clue on where to look.

If the light was out, then started coming on spontaneously, it is an indication of a component failure, and some basic diagnostics, as already suggested, are required.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Sep/27/2022 at 10:19pm
I asked about LED dash lamps because the instrument panel ALT lamp is the signal that tells the alternator to put out current. Filament lamps are low resistance and the alternator on the current draw. 

LEDs draw so little current that the alt doesn't recognize the signal. 

Depends on model and year. I had an LED in my 70 Hornet and. I had to rev it past 2400 rpm at least once, then it would charge. I ended up putting a regular lamp in
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1961 Roadster American, 195.6 OHV, T5
http://www.ramblerLore.com

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Post Options Post Options   Thanks (0) Thanks(0)   Quote amboamx70 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/28/2022 at 7:47am
have not had time to test this week but this is a recent cond. that just happened, have not been working on or changing anything. will try to get some time to test this weekend.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amboamx70 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/29/2022 at 3:03pm
update .. alt. is toast, new one on the way.  Hope it's not junk right out of the box
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