1998 Alternator/Resistor?
1998 Alternator/Resistor? I've heard that to prevent alternator damage on the 1998 alternator I should solder a resistor in the line of the 1 wire plug between the PCM and the alternator.
Is this true, or is this some sort of urban myth?
I know the 1998's are weird, but this just seems strange to me.
I've heard 470 Ohm resistor, and also 4700 ohm resistor.
Which one is the correct ohm, and what watt? They come in all different variations.
Is it really as simple as soldering the resistor in place and no longer burning out alternator after alternator? I've heard horror stories of guys going through 4, 5, 6 alternators in a row before adding a resistor which supossedly takes care of all the burn out problems.
Please, somebody, enlighten me.
Is this true, or is this some sort of urban myth?
I know the 1998's are weird, but this just seems strange to me.
I've heard 470 Ohm resistor, and also 4700 ohm resistor.
Which one is the correct ohm, and what watt? They come in all different variations.
Is it really as simple as soldering the resistor in place and no longer burning out alternator after alternator? I've heard horror stories of guys going through 4, 5, 6 alternators in a row before adding a resistor which supossedly takes care of all the burn out problems.
Please, somebody, enlighten me.
Joined: Sep 2004
Posts: 3,148
Likes: 12
From: Downers Grove, IL
This is not an urban myth. You need a 470 ohm 1/2 watt resistor put in line or you will burn out alternators. If you look at the GM wiring diagrams there is a 470 ohm resistance load in line with the alt (In GM`s case it is from the idiot light in the dash)
Hey I was wondering how far from the connector they put the resistor? I have a 98 harnes I'm about to use and it is missing the Alternator connector and a little wiring. Should I be worried about the resistor missing?
Read the quote, it was the dashlight, not a resistor
Solder one in wherever is convienent for you. 1" or 10' away it makes no difference. Id suggest somewhere it meets up with more harness so you can tuck it in and hide it
Solder one in wherever is convienent for you. 1" or 10' away it makes no difference. Id suggest somewhere it meets up with more harness so you can tuck it in and hide it
if you run the line through your dash light then you don't need the resistor. The bulb takes the place of the resistor. It is sort of nice having a alternator failure charge light, so why not hook it up if one is available?
It has to be a bulb and not an LED.
It doesn't matter where in the line the resistance is.
Not all alternators need a resistor. But certain years of GM alternators definitely do.
It has to be a bulb and not an LED.
It doesn't matter where in the line the resistance is.
Not all alternators need a resistor. But certain years of GM alternators definitely do.
So does the stock 1998 wire run a gauge and a "fail" light, or just a "fail" light?
I was going to wire mine to my stock Mazda voltage gauge..the car doesn't have a fail light. Will it properly supply my voltage meter, or does it ONLY support a dummy light?
I was going to wire mine to my stock Mazda voltage gauge..the car doesn't have a fail light. Will it properly supply my voltage meter, or does it ONLY support a dummy light?
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Joined: Sep 2004
Posts: 3,148
Likes: 12
From: Downers Grove, IL
The voltage meter is supplied by the car wiring, not directly from the alt. The wire on the LS1 alt is not made to supply a gauge. It will not work for your gauge.
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Verdad Gallardo Sorry to have to bring this back up but after looking at my harness I'm a little confused.
One write-up I've seen says to put the resistor in-line between the Alternator plug and Red PCM pin #15. Problem is Red #15 on the 1998 PCM harness goes to fuel injectors and has nothing to do with the alternator.
Does the one wire plug from the Alternator go to the PCM, and then out of the PCM to the "fail" light? If so, where does it come into the PCM at....I don't see it listed on the wiring diagram anywhere. And if it does go to the PCM, does the resistor need to be put between the Alt and the PCM, or after the PCM?
I have a wire coming out from C220 that's supposed to go to the Alt "fail" light....do I just put a resistor on the end of this wire and let it be, or what?
Please inform this novice. I feel so ignorant right now..
One write-up I've seen says to put the resistor in-line between the Alternator plug and Red PCM pin #15. Problem is Red #15 on the 1998 PCM harness goes to fuel injectors and has nothing to do with the alternator.
Does the one wire plug from the Alternator go to the PCM, and then out of the PCM to the "fail" light? If so, where does it come into the PCM at....I don't see it listed on the wiring diagram anywhere. And if it does go to the PCM, does the resistor need to be put between the Alt and the PCM, or after the PCM?
I have a wire coming out from C220 that's supposed to go to the Alt "fail" light....do I just put a resistor on the end of this wire and let it be, or what?
Please inform this novice. I feel so ignorant right now..
Joined: Sep 2004
Posts: 3,148
Likes: 12
From: Downers Grove, IL
On the 98`s the alt wire does not go anywhere near the PCM it goes to the gauge cluster. Put a resistor or lightbulb between C220 pin A and an ignition + 12V source.
Not tryin to side step here.. but for my 1999 Harness I just spliced into the red wire that the Alt goes to the PCM with for the Gauge, and I've had no issues. I figured it would work cause it's a voltage circuit, and it works fine.
Joined: Sep 2004
Posts: 3,148
Likes: 12
From: Downers Grove, IL
Technically that will work to "T" into the wire like that because the PCM is basically supplying battery voltage to that wire on a 99. The gauge may read slightly lower than actual voltage though since there is a 470 ohm resistance load in the PCM between 12V + and that output. However, when you factor in the accuracy of most voltmeters the voltage drop caused by that resistor will not be noticeable.
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Joined: Jan 2009
Posts: 2
Likes: 0
I did place the resistor on the wire and it seemed fine until I hit 3000 rpm then voltage went down to barely 10V and never recovered to 13.5 again...
It has been 3 alternators and I have no idea what to do to get my car fixed...
Please help someone.
It has been 3 alternators and I have no idea what to do to get my car fixed...
Please help someone.
