140 amp Alternator question...

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Oct 26, 2010 | 08:14 AM

81_vette!

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Racer

Joined: Oct 2007

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From: Chapel Hill NC

140 amp Alternator question...

I have a 1977 manual. Electrically stock. No aftermarket stereo.

With the lights/wipers/defrost on at the same time... my alternator is struggling a bit.

I want to replace the alternator, and wanted to know what issues, if any, are there when going from a 70 amp to a 140 amp?

Am I going for over-kill..... would an 85 amp suffice?

Last edited by 81_vette!; Oct 26, 2010 at 08:22 AM.

Oct 26, 2010 | 09:39 AM

7T1vette

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From: Crossville TN

Any alternator will have low output at idle, but the stock alternator should keep up adequately if it is in good condition. I suspect one of the rectifier diodes is bad in your unit. You can either disassemble it and replace the diode sets [not expensive, but a bit of trouble] or you can buy a replacement alternator. If you do not intend on installing electric radiator fans and/or a high-powered sound system, putting a 140 amp alternator in your car is extreme overkill. If you decide to swap it out, go with one or two sizes larger unit. More than that is just a waste of money.

Oct 26, 2010 | 08:20 PM

stellar

Racer

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From: Pgh. Pa.

I agree. The 70 amp lasted over 30 years, so it is probably bad now. 70A or 85A should work fine and save you some money. IMO the 70A was one of the most dependable alts Delco made. The CS144 140A unit is also a great unit and would work well with little modifications. The fit is almost perfect except for the size of the adjusting bolt. A new reg plug connected to your wires and the job is done. There are even adapter plugs made to plug into the new CS144 reg and the other end plugs into your original reg plug. No cutting or splicing. Very clean and easy. The CS144 140A alt is a true work horse. Mark

Oct 26, 2010 | 10:53 PM

mj9311

Racer

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From: bethpage NY

not trying to hijack the OP but i am converting to dual 11'' spalls any recommendations on alt i should run?

Oct 27, 2010 | 10:41 AM

stellar

Racer

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From: Pgh. Pa.

The CS144 140amp should work great.

Oct 28, 2010 | 06:56 PM

jb78L-82

Le Mans Master

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From: RI, Now Franklin/Nashville TN

I ran my OEM 63 amp alternator for years but it would struggle with many accessories running and with my European Hella halogens (80/100 low beam and 100 watt high beams-put them on in 1983). In the early 90's, I purchased a new 12Si 120amp alternator. This alternator was fine when running RPM's but it would struggle at idle (gen light would flicker under extreme load). Last year I installed a 140 amp CS144, easy install with the adapter plug with no other changes. The CS144 is terrific at all RPM's and load for my car, even at idle. I purchased the CS144 here:

http://store.alternatorparts.com/

I paid $169-new!

Oct 28, 2010 | 10:14 PM

Imo Apita

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120 Amp alternator for $67.50

http://cgi.ebay.com/ebaymotors/GM-CH...Q5fAccessories

Oct 29, 2010 | 02:58 PM

jb78L-82

Le Mans Master

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Posts: 7,470

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From: RI, Now Franklin/Nashville TN

Quote:

Originally Posted by Imo Apita

120 Amp alternator for $67.50

http://cgi.ebay.com/ebaymotors/GM-CH...Q5fAccessories

As I said above, a 12SI alternator upgraded to 120 amp alternator capacity will not put out sufficient power at idle. I had a 12SI 120 amp alternator and it was not up to the task for my car at idle. Switched to the CS144 alternator which is a MUCH better alternator than a high output 12SI that has been modified for high amperage and the CS144 charges like a champ at IDLE under full load. You get waht you pay for! The CS144 alternator is a superior alternator all the way around to a 12SI, no comparison.