Eliminator89 Posted August 30, 2007 Share Posted August 30, 2007 How do I determine the amperage rating of my alternator? Link to comment Share on other sites More sharing options...
Oizarod115 Posted August 31, 2007 Share Posted August 31, 2007 local auto places do alt. testing so you COULD hypothetically speaking remove it and have it tested i bet that would tell you exactly what its actually putting out. what engine, a/c? options like that can affect alt. size a 4.0 with a/c is a 100amp-ish alternator Link to comment Share on other sites More sharing options...
HOrnbrod Posted August 31, 2007 Share Posted August 31, 2007 If it's on the vehicle, easiest way is to wriggle a mirror up in there and see if you can read the part number, then cross reference it. Link to comment Share on other sites More sharing options...
Oizarod115 Posted August 31, 2007 Share Posted August 31, 2007 well on rockauto the ones offered for replacement on a 89-4.0L manche are 100A, 61A, 85A didn't check any other years/motors though Link to comment Share on other sites More sharing options...
Eliminator89 Posted August 31, 2007 Author Share Posted August 31, 2007 Well I have the 4.0 A/C Fog lights and bed light. No electric windows or locks. I'll have to see if the part number is readable and check that. I may not need a new one, I have to check the connections for corrosion first. It worked fine but now with the lights on, the wipers running and the heater blowing the voltage keeps dropping. It isn't putting out much. It catches back up as I turn stuff off. I was just looking on car-part.com and came up with about 8 different ratings and had no idea what mine might be so I thought I would ask. Link to comment Share on other sites More sharing options...
Oizarod115 Posted August 31, 2007 Share Posted August 31, 2007 Well I have the 4.0 A/C Fog lights and bed light. No electric windows or locks. I'll have to see if the part number is readable and check that. I may not need a new one, I have to check the connections for corrosion first. It worked fine but now with the lights on, the wipers running and the heater blowing the voltage keeps dropping. It isn't putting out much. It catches back up as I turn stuff off. I was just looking on car-part.com and came up with about 8 different ratings and had no idea what mine might be so I thought I would ask. my truck is 4.0L (had) a/c, no electric locks/windows and has the 104amp alternator (i know cause i replaced the old one) with wipers, blower on 3, lights, dual electric fans, and cd player/small sub going its low on the gauge but not below 12, probly say 12.5ish (that was this afternoon) Link to comment Share on other sites More sharing options...
SomeNew Name Posted August 31, 2007 Share Posted August 31, 2007 yeah, that sounds like you're over drawing.. if you were to do an electrical load analyst, you would probely find that with your heater, fogs, and misc on that you are drawing more than what you're putting out.. so if you were drawing 75A with all that stuff on and you only have a 61A alt you're drawing way too much off it that the alt can't keep up... if you can't do a load analyst then I would tell you to get a bigger alt cause it sounds like you're over drawing.. What we do in the case of Aircraft is we do a load check and if we find out that the A/c is drawing too much we change the Starter Generator to a higher output, (IAW the applicable standards of airworthiness) and leave a plus 10% buffer. Link to comment Share on other sites More sharing options...
DirtyComanche Posted August 31, 2007 Share Posted August 31, 2007 The 100A~ models seem to typically be stamped with a 100A, or something close to that, marking. Never have I seen a 61A version stamped. I always get the ones that have the 100A stamping on them out of the boneyard. Link to comment Share on other sites More sharing options...
CWLONGSHOT Posted August 31, 2007 Share Posted August 31, 2007 Well I have the 4.0 A/C Fog lights and bed light. No electric windows or locks. I'll have to see if the part number is readable and check that. I may not need a new one, I have to check the connections for corrosion first. It worked fine but now with the lights on, the wipers running and the heater blowing the voltage keeps dropping. It isn't putting out much. It catches back up as I turn stuff off. I was just looking on car-part.com and came up with about 8 different ratings and had no idea what mine might be so I thought I would ask. my truck is 4.0L (had) a/c, no electric locks/windows and has the 104amp alternator (i know cause i replaced the old one) with wipers, blower on 3, lights, dual electric fans, and cd player/small sub going its low on the gauge but not below 12, probly say 12.5ish (that was this afternoon) Also, don't take the reading from factory gages as gospel!! They will merely offer referance and even then can be WAY OFF!!! Unless you running a good quality after market gage wired correctly. Direct to batt for a volt meter OR one side to the batt and ALL electrical draw items threw the other side for amp meter. Just FYI... Link to comment Share on other sites More sharing options...
Eliminator89 Posted August 31, 2007 Author Share Posted August 31, 2007 It just recently began doing this. I can see the wipers slowing down as the voltage gets lower and lower. Its just not putting out the amps it used to. It used to keep up just fine. First thing is to check the rating and also the connections while I'm under there. If cleaning the connections doesn't help, then off to the rebuilder with it for a check up. Link to comment Share on other sites More sharing options...
mjtjnj Posted August 31, 2007 Share Posted August 31, 2007 rebuilder? Cheaper and easier (with warantee) just to buy an Autozone/Pep Boys unit, and pick your amperage. Link to comment Share on other sites More sharing options...
Eliminator89 Posted September 1, 2007 Author Share Posted September 1, 2007 The rebuilder is a local fellow and I have known him for better than 10 years. I have more faith in his rebuilds than anything other than brand new. He really is very good. He knows how I like my stuff done and if there's anything amiss with the parts, he'll tell me if going new is better. Looks like I won't have time to check it out 'til Sunday. I have to work tomorrow. The local flood has us VERY busy. Getting power back on for folks is more important than my lazy alternator. Link to comment Share on other sites More sharing options...
CWLONGSHOT Posted September 1, 2007 Share Posted September 1, 2007 Check the wires and connections as well. get your self some dielectric grease and use it. CK the power line from the alt. If its black inside thats corrosion and will impeed flow and raise impeedance overlowering the amount of "juice" that gets to your batt. I made my own and changed all my battery cables and alt wires some months back. I also upped the size on all. I added a BIG alt and this required a #6 wire for the alt. The jeep starts better and even the motor runs better !! CW Link to comment Share on other sites More sharing options...
Eliminator89 Posted September 2, 2007 Author Share Posted September 2, 2007 Alternator took a dump this morning. :cry: No time now to take mine to the rebuilder. "Hello, AutoZone?" Link to comment Share on other sites More sharing options...
Eliminator89 Posted September 2, 2007 Author Share Posted September 2, 2007 All better. Bought a new 100 amp'er this morning, got it installed. Having a cigar to celebrate.. :chillin: I'll have the old one rebuilt and stick it on the shelf. Link to comment Share on other sites More sharing options...
carnuck Posted September 4, 2007 Share Posted September 4, 2007 I did the 130 amp upgrade, but haven't done my wires yet (got to avoid any heavy electrical draws until then) Link to comment Share on other sites More sharing options...
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