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70 ambassador 360 alt light on |
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amboamx70
AMC Apprentice Joined: May/05/2017 Location: elmwood il. Status: Offline Points: 33 |
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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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nickleone
AMC Addicted Joined: Oct/04/2008 Location: westminster co Status: Offline Points: 1429 |
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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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nick
401 71 Gremlin pro rally car sold 390 V8 SX/4 pro rally car sold 1962 Classic SW T5 4 wheel disc brakes |
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tomj
AMC Addicted Joined: Jan/27/2010 Location: earth Status: Offline Points: 7522 |
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Did you replace dah indicators eith LEDs lately?
What changed recently?
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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sweatlock
AMC Addicted Joined: Apr/28/2014 Location: Largo, FL Status: Offline Points: 3285 |
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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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Trader
AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6755 |
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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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Goodtimes
AMC Apprentice Joined: Oct/27/2020 Location: Wisconsin Status: Offline Points: 115 |
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Agree with sweatlock, condition normal, alternator needs higher RPM to start charging
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69 AMX 290 4spd leather
68 AMX 390 A/T 70 front |
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bigbad69
Supporter of TheAMCForum Joined: Jul/02/2007 Location: Ottawa, Ont. Status: Offline Points: 6609 |
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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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69 Javelin SST BBO 390 T10
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tomj
AMC Addicted Joined: Jan/27/2010 Location: earth Status: Offline Points: 7522 |
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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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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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amboamx70
AMC Apprentice Joined: May/05/2017 Location: elmwood il. Status: Offline Points: 33 |
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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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amboamx70
AMC Apprentice Joined: May/05/2017 Location: elmwood il. Status: Offline Points: 33 |
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update .. alt. is toast, new one on the way. Hope it's not junk right out of the box
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