alternator. keeps puking

[scoyote]

I updated my electrical with a serpentine setup from a 1991 suburban and I keep burning alternators. The 1972 blazer has a 2 wire system and the 1991 alternator has 3 wires and I have been just leaving one wire blocked off. Charges perfect but keeps burning alternators. Anyone been through this before?

[truckdude239]

where are you geting teh alt from? i had an issue with advance auto where i got 5 yes 5 bad alts, but from the sound of it it is not wired right and in full 100 percent charge mode

[truckdude239]

l;ook here is a wiring diagram for the cs style alterantor you have its the bottom one on teh post

[scoyote]

I'll check the link, thanks. I use NAPA Gold alternators......its gotta be something else

[dwcsr]

connect the third wire or convert to a single wire. Sounds like you have capped off the sensing wire and the ALT doesn't know when to shut down.

[VetteVet]

I went through your build thread and didn't see how you wired the alternator. Could you show how you wired it and did you install the extra resistor in the wire that goes to the L pin in the alternator? The alternator will charge without the resistor but it won't last very long.

[Greenlee]

I seem to remember reading somewhere there is a difference in the alternators when GM went to the serpentine setup - external regulator vs. internal regulator. I have seen a wire pig tail adapter to make the swap on Summit Racing's site.

[jjzepplin]

Originally Posted by VetteVet

I went through your build thread and didn't see how you wired the alternator. Could you show how you wired it and did you install the extra resistor in the wire that goes to the L pin in the alternator? The alternator will charge without the resistor but it won't last very long.


Attachment 1269625

I did mine exactly like this (with help from VetteVet) and it works awesome.

[scoyote]

VetteVet seems to have the answer I'm looking for. I'll give that a try. Thanks for the help!

[jjzepplin]

DID this get fixed?

[gmachinz]

If you look at the GM assembly manual for factory equipped internally regulated alternators on vehicles with stock gauges and not lights, the length of the stainless resistance (sensing) wire is approx. 10 ohms similar to what GM did with pre-HEI externally mounted coils. If you opt not to use this wire, you must use a 10 ohm resistor inline or a blocking diode works as well but a resistor is just as good. If unsure, install a resistor anyway for safe measure.

[VetteVet]

That's fine for the 10 and 12 SI alternators but the CS and later styles require a larger ohm resistor. Painless recommends an 85 ohm 5 watt and others have used 1 watt and 300 ohm resistors. I wouldn't put a 300 ohm in because it might restrict the trigger voltage too much. I have read that 35 ohm is the minimum so I'd go with the near 100 ohm depending on what I could find.