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1990 K5 Alt Charginh

Justin Fleming

Justin Fleming

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Does anyone know if the switched poewr signal to the alternator is fuese anywhere? It is my understanding that you need 12v with the key on to turn the alt on, in lamins terms. Brand new alt and still no charging. So I need to figure out the 12v switched power....

thanks
 
1990 I believe used the dash light to excite the alternator, if that's the proper term. Does your battery/charge light in the dash work?

Would seem ridiculous that a simple bulb failure would cause a no-charge condition from a manufacturer standpoint, but that is the reason a resistor is used in the CS alternator swaps...
 
dyeager535 said:
1990 I believe used the dash light to excite the alternator, if that's the proper term. Does your battery/charge light in the dash work?

Would seem ridiculous that a simple bulb failure would cause a no-charge condition from a manufacturer standpoint, but that is the reason a resistor is used in the CS alternator swaps...
Click to expand...

Funny you say this, my backlighting in the dash went out as of recent. Then I was stranded the next day. I have two 1000cca batteries, so it is possible I have been running off batter for a day or so. Maybe the fuse went for the dash lights? In my mind I was chalking up the dash lights going out to a possible bad dimmer switch.....Hummm
 
what can you tell me about the cs alternator swap? I have a CS144 modified high out put alternator on there currently...
 
Just talking about a swap from the 10/12SI setups to the CS 130/144's in earlier rigs. Electrically really nothing to the swap other than needing resistance on one of the wires to get it charging. IIRC, even the earlier alts used a charge light though...I can't remember.

Again, to me it seems really odd that a bad dash bulb could potentially leave a customer stranded, but from pretty much all I've read/heard/seen, that charge/alt light in the cluster is necessary for the alternator to charge.
 
dyeager535 said:
Just talking about a swap from the 10/12SI setups to the CS 130/144's in earlier rigs. Electrically really nothing to the swap other than needing resistance on one of the wires to get it charging. IIRC, even the earlier alts used a charge light though...I can't remember.

Again, to me it seems really odd that a bad dash bulb could potentially leave a customer stranded, but from pretty much all I've read/heard/seen, that charge/alt light in the cluster is necessary for the alternator to charge.
Click to expand...
Copy.... thanks for the info....
 
I believe that is how it should operate. Key on/engine off, light should be on.

Someone else may want to comment, I don't have a charge light setup in my truck.
 
Also can anyone add to it..... Is there a fuse in the fuse panel asscoiated with this circuit?
 
Gauge fuses,,, I had problems awhile back that for some reason the gauge fuse would burn out, and I found out when it did that, the alternator would stop charging.
 
4xcrazy said:
Gauge fuses,,, I had problems awhile back that for some reason the gauge fuse would burn out, and I found out when it did that, the alternator would stop charging.
Click to expand...

Thank you, did you resolve the issue of the gauge fuse burning out? What was the outcome?
 
Nope, never found it, but hasn't done it in a long time. I'm thinking it was an obvious short somewhere int he harness, and since I have had it removed a few times trying to find a separate problem, I may have inadvertently fixed it.
 
So here is the skinny, my 5amp fuse was blown, replaced and now I have the dash lights back. I don't have the alt charge light as I have the volt gauge. I have 12v to ground on both terminals that should excite the alternator with the key on and engine off and key on engine running. What was happening with my last alternator is that it would charge then drop below 12v and charge and drop below 12v no charge. So I put the new alternator on and it was good for a few weeks and has stopped charging. However I just pulled it in the garage and it was above 13v then dropped and then above 13v and dropped again. It will not charge any more.

Where is the resister that everyone discusses?

I am at a loss any help would be appreciated....
 
The two pin connector is a pink wire and a brown wire. It looks like the pink goes into the main fire wall harness and the brown goes to the wire bundle back by the distributor and I cant quite trace it after that....
 
further trouble shooting show that after replacing the fuse, and getting my dash lights back, the alternator output stud is producing 14.4v. but my gauge in the truck is not reading properly. What's odd is that it does drop to zero with key off and goes to what I would guess is 10v to 11v on the gauge when truck is running. So the gauge is doing something..... Hummm
 
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So I will tear into the dash tonight and track down the volt gauge issue. If it is anything like my 86 the gauge just has two post off the back of it that pushes in to the steel pinch clamps. Does anyone know if I check the pinch clamps with a volt meter if it will be actual voltage or is it stepped down some how to work with the calibration on the gauge? Also does anyone have a replacement gauge laying around
 
ALL the gauges run off 12V and ground.

I don't know everything about every truck out there, but I'm certain you have a charge indicator, I've taken enough of the 90-91 clusters apart (all gauges) to be confident in saying it was standard. It's where the clock used to be, lower left portion of the cluster. Without looking at my pics from my cluster hardwiring, there were three positions for bulbs there (which is why you can't easily add the earlier tach cluster small fuel gauge there like you could earler), but "standard" trucks only used the charge indicator light in that position.
 
Ok, I will investigate that tonight when I tear it apart. There is a lower left position, which I always thought it was just a blank if you will. I will follow up this weekend some time.

thanks again.
 
For clarification, all the gauges have 12V and ground, the voltmeter is the only one that doesn't have a third "leg" of course.

Unfortunately I don't have a picture of the PCB on the back, but by at least 1990, perhaps a bit earlier, the power and grounds were all(?) combined on the clusters, so if only one gauge is malfunctioning, pretty likely it's due to the little clips that it makes contact with. Quite rare for a gauge to actually fail, although that is possible.
 
dyeager535 said:
For clarification, all the gauges have 12V and ground, the voltmeter is the only one that doesn't have a third "leg" of course.

Unfortunately I don't have a picture of the PCB on the back, but by at least 1990, perhaps a bit earlier, the power and grounds were all(?) combined on the clusters, so if only one gauge is malfunctioning, pretty likely it's due to the little clips that it makes contact with. Quite rare for a gauge to actually fail, although that is possible.
Click to expand...

I just cant get my head wrapped around how it is reading partial 8-10v, just not actual voltage being produced. Additioanlly everything else I have read states that if the indicator lamp is blown it wont charge either. Well I dont have a indicator lamp lightup and I am certainly getting the 14.4 volts on the stud, therefore the excite to the alt is working....
 
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