85' Alternator replacement
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From: Winter Haven Florida
85' Alternator replacement
I brought the 85' a month ago and I am changing out my alternator due to charging problems. I just went and ordered a replacement one for the correct year. But when I went to do the swap I found that the plug would not fit the new alternator. when I went back to the auto part store to make sure I got the correct one they searched the part number 7935-11 on the old one and found that it is from a 1988-1990 Corvette. I checked the plug and and harness on the car and found that a previous owner changed the plug. Can anyone tell me if it is OK to keep the same 1988-1990 alternator or switch back to the original one. They are both the same amperage.
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I brought the 85' a month ago and I am changing out my alternator due to charging problems. I just went and ordered a replacement one for the correct year. But when I went to do the swap I found that the plug would not fit the new alternator. when I went back to the auto part store to make sure I got the correct one they searched the part number 7935-11 on the old one and found that it is from a 1988-1990 Corvette. I checked the plug and and harness on the car and found that a previous owner changed the plug. Can anyone tell me if it is OK to keep the same 1988-1990 alternator or switch back to the original one. They are both the same amperage.
Last edited by WVZR-1; Apr 22, 2014 at 08:30 PM.
Safety Car
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From: Melbourne, Victoria, Australia
I brought the 85' a month ago and I am changing out my alternator due to charging problems. I just went and ordered a replacement one for the correct year. But when I went to do the swap I found that the plug would not fit the new alternator. when I went back to the auto part store to make sure I got the correct one they searched the part number 7935-11 on the old one and found that it is from a 1988-1990 Corvette. I checked the plug and and harness on the car and found that a previous owner changed the plug. Can anyone tell me if it is OK to keep the same 1988-1990 alternator or switch back to the original one. They are both the same amperage.
You will need the adapter harness, the 86-91 alternators will not charge without the correct resistance that is in the factory engine harness. You can buy the adapter and plug the adapter harness in and it will work. Or you can fit any 12 volt lamp to terminal L to make it work.
http://www.ecklerscorvette.com/corve...1969-1986.html
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Hi
You will need the adapter harness, the 86-91 alternators will not charge without the correct resistance that is in the factory engine harness. You can buy the adapter and plug the adapter harness in and it will work. Or you can fit any 12 volt lamp to terminal L to make it work.
http://www.ecklerscorvette.com/corve...1969-1986.html
You will need the adapter harness, the 86-91 alternators will not charge without the correct resistance that is in the factory engine harness. You can buy the adapter and plug the adapter harness in and it will work. Or you can fit any 12 volt lamp to terminal L to make it work.
http://www.ecklerscorvette.com/corve...1969-1986.html
It seems the change had been done previously to the OP's car and it would seem to have been operational so he should only need to replace with what he removed. He removed '88+ so put the same back. Now if his "take off" checked fine then maybe the upgrade wasn't completed properly and then the harness would be a theoretical fix and there would be no need for the buy of the alternator that he's anticipating. But if there were "cuts and splices" done to accommodate the change then he needs to rethink the entire operation.
He should be able to inspect. correct and do the part/harness or whatever locally! He should be able to just add a resistor also to correct it. It's been awhile since doing an SI to a CS. The OP just needs to check the way the upgrade was made.
I believe that the CS wants to see 47 Ohm resistance so a 50 Ohm resistor is added either with a lamp (as you mentioned) OR without one if your not concerned with a warning light.
All of the wiring possibilities are covered here nearly at the end of the tutorial with schematics that might help the OP. Nearly at the end. It's a good read anyway! Just look for WIRING - PLFS/PLIS
http://www.pirate4x4.com/tech/billav...art2/#csseries
Last edited by WVZR-1; Apr 23, 2014 at 08:07 AM.
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From: Winter Haven Florida
Here is a picture of the plug that the previous owner spliced into the harness. For me to use the harness adapter I would have to change back to the factory plug. And wouldn't the resistor be in the plug?
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First thing - have your old alternator checked to be assured it's either good or bad and if there's doubt I believe I'd hang on to it until the operation is done. What are the wire colors behind the crimped butt connectors? Resistance isn't necessarily in the connector. How is your older alternator lettered PLFS or PLIS?
I doubt the resistor in the connector if it were just a basic service connector.
Take a look at the link I put in my last post.
I doubt the resistor in the connector if it were just a basic service connector.
Take a look at the link I put in my last post.
Last edited by WVZR-1; Apr 23, 2014 at 08:55 AM.
Thread Starter
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From: Winter Haven Florida
Had the old alternator tested, it failed three times. The color of the wires in the harness are the same as on the plug red and brown. And my alternator connector plug is a PLFS as well as the new alternator.
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Match the L location in your connector and I believe you'll find it empty. If it's empty then either add a bulb or a 50 Ohm resistor to that as referenced in the PLFS wiring in the link I included. Same as "gerardvg" mentioned doing. I believe the alternator may function "as is" but I believe it leads to very early failure. Maybe buy another connector with either three wires or four and then just use the ones you need and clean up the splices maybe with some solder or at least some heat-shrink. A new connector should be very inexpensive.
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From: Winter Haven Florida
I checked the connector and the the L location is not empty. But I will keep an eye on the voltage to see what happens. Also I think the reason the old alternator was bad from the car sitting for so long. I did buy the car from a local parts yard.
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have the electrical load tested on the car and have them confirm voltage at the battery when running. Turn on all of the lights, radios, wipers and anything else you can think of and at maybe 2000 RPM have them tell you what amperage the alternator is doing under load.