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Low Alternator output at idle |
Post Reply | Page 123 4> |
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ddfarm
AMC Nut Joined: Nov/23/2009 Location: Virginia Status: Offline Points: 315 |
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Posted: May/23/2011 at 6:16am |
I checked out the Alternator shop and they are telling me that it is NORMAL for these alternators to "cut out" around 700-600rpms considering the size of crank shaft pully used on AMCs. Can anyone tell me if this is true? If it is true, then my problem is not the alternator nor the regulator.
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cindys1971
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ddfarm
AMC Nut Joined: Nov/23/2009 Location: Virginia Status: Offline Points: 315 |
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Thanks, the specs would be great. I have already tried 3 regulators and all produce the same thing. And not all these regulators were bought from the same place.
I might add to my observations. @900 rpms with everything OFF the volage from the back of the alternator is 14.1
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cindys1971
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billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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There is a thermistor in the regulator. When it's cold, it charges about a half volt or so higher (I'd have to refer to my Motorola references to get the temp and voltage charts.) As it warms up (ambient temp warms, as in under-hood temp) it drops the charging rate (voltage) The reason is that cold batteries take more to charge. That's one reason the regulator is near the battery. In any case, 13.6 or whatever you stated is low. It should be up higher than that. I'll get the exact specs for your alternator later tonight if I remember. |
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69 ambassador 390
Supporter of TheAMCForum Joined: Nov/22/2009 Location: Peoria, AZ Status: Offline Points: 3539 |
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Try a different regulator. They are temperature regulated and there may be a malfunction.
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Steve Brown
Algonac, Mi. 69 Ambassador sst 390 84 Grand Wagoneer 69 Cougar XR7 65 Fairlaine 500XL 79 F-350 Super Camper Special |
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ddfarm
AMC Nut Joined: Nov/23/2009 Location: Virginia Status: Offline Points: 315 |
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Not real sure but I think they had a chart for this alternator. I will check tomorrow. Can you answer the questions in my last post without this info from the shop/
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cindys1971
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ddfarm
AMC Nut Joined: Nov/23/2009 Location: Virginia Status: Offline Points: 315 |
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cindys1971
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poormansMACHINE
AMC Addicted Charter Member Joined: Jun/28/2007 Location: Shoemaker-Levy9 Status: Offline Points: 12302 |
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Smaller pulleys work nice on paper but now you have less less area for the belt to actually drive a greater load that you're introducing so it will slip.
What rpm and load is the shop testing the alternator at that your home made test isn't? |
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ddfarm
AMC Nut Joined: Nov/23/2009 Location: Virginia Status: Offline Points: 315 |
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I still have the problem!!!!! Here are some other facts that I have done/found during my ordeal.
Cleaned and tested every ground under the hood. Had alternator and regulator checked at the alternator shop, which checked out OK. Tried a smaller pulley from 2 5/8 inch(orginial) to 2 inch with no noticeable difference. 2" is smallest available. Here are the results with the orginal pulley with car in gear. Test 1=@600 rpms alterantor works great with Lights-off, fan-off......13.9 voltage at back of allt Test 2=@600 rpms alternators works great with lights-off, fan-on......13.8 Test 3+@600 rpms alternator stops putting out with lights-on, fan-on......12.1 at back of alternator and working strickly off the battery. No help from alter With car in neutral and rpms @900 I get 13.7 volts at back of alternator even with everything on. What other test should I do? Are the lights pulling too much Voltage? What should the voltage be at the yellow wire going into the regulator even when the lights are on? If this voltage is below 12 volts would the alternator stop output. If so at what point would it drop out? |
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cindys1971
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billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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No, the alternator is the "driven" pulley...... look at the cam to crank ratio, or a multi-speed bicycle... you derail the chain to a larger diameter sprocket to slow it down, and gain power. To make the alternator spin faster, you decrease pulley size, like you'd decrease rear sprocket size to make the bike move further for every push of the pedal crank. |
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BDCVG
AMC Addicted Joined: Dec/19/2007 Location: Endless Mtns. Status: Offline Points: 993 |
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1970 AMX 390 5 spd full Control Freaks front and rear suspension
2014 E63 AMG-S wagon 1965 Austin-Healey 3000 MK III |
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