CELEBRATING 20 YEARS!

This is for my 87'LS with the 88'92' f-body serpentine bracket and CS alternator. I previously had the 87' Monte stock setup with a 87' TPI alternator(one year only CS style) that worked with the mostly stock Monte accessory setup, just a longer belt and 87' TPI alternator bracket. The wiring for that was simply the adapter harness into the stock SI connector and it worked fine.

Once I converted to the 88'+ serpentine setup just using the connector didnt work, for whatever reason. Instead I had to run a wire directly to an ignition source in the fusebox for it to hold a charge. Is this just a difference in alternators? I can't see why one car would be different than the other.

Curious how those with CS alternators wired them up in their Montes.

Did you use a resistor PaulB? The CS style requires 35 ohms of resistance between the tickler wire and battery post. The stock SS (and I assume LS) dash setup with gauges provides only 10 ohms. I was having on again, off again charging issues with my CS alternator until I added a 27 ohm, 1/2 watt resistor in series with the tickler wire. Never had a problem since.

I have a feeling some CS alternators are more sensitive to this resistance issue than others. That would explain why some guys don't have problems (getting by with the 10 ohm resistance) and some do (having to add resistance). I have a feeling in your previous case, the added wire to get to the ignition source provided just enough resistance to satisfy that particular CS unit. Try adding a resistor. Cheap and easy to do.

It has a resistor already in it on the adapter harness, not sure the ohms on it but its there...I could try one of mine since it doesn't take much, might swap my *spare* alternator onto it as well and see what happens.

Some will need the resistor and some wont, Just a luck of the draw type of thing. Mine is out of a 92' C2500, 120AMP alt. I just ran the one RED lead from the battery, and then the connected the original ALT wire from the Monte to the Brown wire on the CS plug, also the little red wire goes to the post on the back of the ALT, with the lead from the battery mentioned earlier. You should here the ALT "excite" when you turn the key to the ON position. Mine has been running for 8 months with no issues, and no resistors.
HTH
Chris

Thats the thing that kind of scares me, the alternator with the ignition on makes some noise, like a light humming. Just doesn't seem right. On my SS I had the same humming withOUT the ignition on due to using the wrong CS harness from another GM car(wrong PIN's) and it burned the alternator up. Fixed that but for the LS I dunno...

The wiring is different stock for both the 86' and 87' which is odd. The 86' IRC has the battery lead then just the wires from the SI harness going back to the firewall. The 87' has the battery lead then off the SI connector the red wire going back right to the alternator post with the battery lead like you mention. Then the brown wire into the firewall....

I will try my other alternator and checking out the resistor situation, but the car holds a charge fine. Just the humming noise and not being exactly sure how to properly wire it is making me confused . I know I shouldn't have to wire the alternator directly to an ignition source in the fusebox but I am in order for it to hold the charge .

Bringing this one back from the dead as I seem to be having a similar problem.

This is regarding a stock (B-body) CS130 alternator on my 91 B-body serpentine setup. It is wired with the proper resistor harness (Delco 8078/GM 12102921). The alternator does not seem to be charging - I am only reading 10V or so at the battery (and alternator) with the car running. Turn on the brights, and that nosedives to 6V or so (this is how I noticed it, the lights drained the battery and dimmed down).

http://www.alternatorparts.com/cs130_sbpage3.htm


Following the link above, I seem to be having a problem with the factory brown exitation wire - there is no voltage here with the key in the on position. The odd thing is, I never had a problem with the old SI alternator. I checked for voltage at the factory SI connector.

I will have the alternator checked since it was used and came with the setup, so it's condition is unknown - could have easily been damaged from bouncing around in shipping. I think I might have a wiring issue though since I do not have voltage at the brown wire (terminal L in diagram). I have confirmed that it is an open cct rather than a ground since there is infinate resistance between this same L terminal and ground. Gauges fuse checks out ok.

The factory wiring diagram shows the cct running through the "generator indicator" and has the same diagram for both gauge and non-gauge applications. I am assuming the generator indicator on an SS is indeed the voltage gauge, which is kind of flakey on my car. I know it's the (pathetic) main pod connection as I can play with the lower corner of the pod and the voltage gauge will move. I am suspecting a poor connection here is where my issue may lie. What baffles me is why this was never a problem with the SI alternator.

PB, what is the voltage from the brown wire, at the alternator? When running, what is the output of the alternator; at the battery? I also worry about those adapter harnesses. We're relying on a 20-year old, dual spade connector, making good contact. That's why I just hard wired the CS-style connector into the wiring. I've tried 3 different alternators (recently a Powermaster) w/o a problem. I didn't use a resisitor either. This resistor stuff is confusing me now!

Does anyone know what the minimum voltage required at the exciter wire is? The site above seems to suggest that as long as it's not zero then your ok - I am getting about 6mV, which I am think is still not enough, especially since I am measuring before it hits the (~500ohm) resistor in the conversion harness. It's now getting 12.3V while running at the rear of the alternator and at the battery, and only about 11.6V with the brights on. These numbers are still too low obviously.

I brought the alternator to two locations (same chain) to be tested - the first place said it was no good, and the second guy said it tested fine. I am sure the first guy just screwed up one of the connections (and I couldn't see the screen when he did it either).

If the CS130 is good, it will work correctly if it has a switched 12V going through a 470 ohm, 1/2 watt, resistor to pin B. All the people that put an LS engine with a carb setup in an older car have to do this to get it to charge without burning up the alternator. Without the resistor inline, the alternator will be on borrowed time. With the resistor inlne, you will probably get around 10 volts to the alternator to (turn it on).

Thanks Larry - I've either got a bad alternator or some wiring issues (I am thinking the latter). My father was over the other day and I checked the voltage at his exciter wire (88 Caprice) and he only had 0.3V or so - so I'm a little confused on what the minimum voltage needs to be here. Now I am getting much less than that even with only 6mV or so. I also tried another known good battery so I know that it's not the issue. My gauge has always read low, but we all know how crappy the factory gauges are. That may have something to do with my problem here obviously, but I just don't really understand why it was never an issue with the old SI alternator. It seems there is possibly too much resistence in the circuit.

If anyone has access to their Monte, I would be curious to hear what voltage you are getting at the exciter wire with the harness unplugged and the key in the on position. Numbers from SI (original) alternators will also help as I can compare with the voltage before my adapter harness.

Stock SI harness: From brown wire (pin 1) to ground
OR
CS harness: from brown wire (pin L) to ground

I don't even remember what I did on the LS now, even though its been 3 years I'm a bit dissapointed I forgot . I think I stopped using the adapter harness but put a resistor in. If I get a chance I will unbury the Monte in the garage and test it out.

Let me know what you find if you get a chance Paul - from your description above, it sounds like we may have had a similar problem.

Powermaster recommends 47 ohms total, through the "tickler" wire.

The GM harness has nearly 500 ohms of resistance itself.

Just got out to my car. I had to uncover the garage door from under all this white stuff!
Anyway, Exiter wire voltage with harness unplugged from the alt. is right at 12v.

Brown wire is at 12.5v on the si side, & after the adapter it's at about 11.8v

Anything else you need to know? I've finished my swap & all is working fine.

Thanks Jonathan! That answers my question, and I definitely have some issues with the factory wiring to track down then. Strange how my fathers' car also has very low voltage there as well.

In looking at the factory manual, I see there is also a diode located somewhere in the cabin side of the circuit, which has me wondering if it has seen better days. Should be fun trying to find the darn thing though. Worse case, I'll run a new switched source through the adapter, but I would rather get it working correctly.

I've actually noted something about the the 86 & previous SS's compaired to the 87/88's. I don't know if it might be contributing to your issue or not.
The exiter wire seems to go to different locations. Not sure if the're all like this or what. On the older, it goes I assume to the starter, & gets triggered from there. My 84 Caprice was like this as well.(see picture jigsaw posted in the link) http://www.montecarloss.com/community/ub...6330#Post516330 Where as the the 87/88's just have a short loop wire from the pigtail connector on the alt. to the Batt. post on the back. I do realise this should work the same way, but could you have a issue with the connection on the exiter wire at the starter? Maybe try just try running a temporary loop wire from the exiter to the Batt. post on the back of the alternator & see if it makes a difference.

I think we are mixing up some terminology here - maybe I'm screwing things up here, but I was calling the brown wire the exciter wire, which "turns on" the alternator.

I do have full voltage at the red wire - and on my car a feed comes direct from the POS battery cable to the BATT terminal on the alternator, with a short loop to the alternator connecter (as you describe the 87/88's). It's the brown wire where I have the extremely low votlage, causing the alternator not to charge.

I found part of the factory manual that states there should only 2-4V at the brown wire. I just tried running a 12V source before the adapter harness to see if the alternator would charge and it did (about 14.6V). Gauge also read over 13V - I'll have to study the diagram to try and figure out where the problem may lie in this circuit.

That diode is in the main harness just before the fuse box - with how taped up it is, it may be impossible to reveal it. Too bad GM made the C100 connector so hard to get at - would be nice to check voltage here to help track down where the issue lies.

I do have a switched 12V source running right by the alternator for the electric fan - I may end up just tapping off here.

Ah. So we DON'T want low voltage there, huh? We want and need around 12 volts?

The factory troubleshooting section says it should be between 2 and 4V rather than 12V, but I think anything lower than the system voltage will do (I could be wrong here).



Here is an older diagram on maliburacing:


...and here are the diagrams in my 85 shop manual:


If you compare them, I think my shop manual may actually be missing some information on the (lower) diagram listed for the VIN G (SS) cars. I believe it should show the resistance wire for cars with gauges, just like the VIN 7 (upper) diagram and the maliburacing diagram. I am pretty sure if that's the case, then my resistance wire (brown/white) from the ignition switch is shot.

OK, I'm officially confused. I made a mistake in my last post & I was calling the RED wire the exiter wire. From hence forth, I will simple call the wires by their color. I checked again, & the brown wire had 12.5v at the si side, & 11.8v after the adapter. From what I see, you're saying it should only be 2-4v?

That's what the GM shop manual says - I'm curious what other people might have here. If yours is working and charging properly, I wouldn't worry about it though.

Well I found my particular problem - a previous owner/mechanic.

The brown/white wire should be mated to the orange wire at the ignition switch as shown in this diagram on maliburacing and upper VIN 7 diagram above. I confirmed this with the harness from my old parts car (so yes, I am now sure the VIN G diagram in my 85 shop manual is wrong). I'm glad I figured out this error before tearing the gauge pod apart to diagnose this.

I dropped the column and you can see that there WAS a brown wire mated to the orange wire, but has been snipped off. Fine, all I have to do is peel back the wrapping on the factory harness and the wire should be in there somewhere right? Nope. Pulled it back a few inches (about as far as I can without removing the dash) and nothing. I'm going to try again later, but I think I am out of luck for finding the wire where it enters the harness. I can however, barely see it where it enters the C100 block at the other end (still in the cabin) though, so if I have to I will snip the wire there and run a new wire over to the orange connector at the ignition switch, bypassing the portion that runs through the factory harness. I really don't want to have to do this, but I'm not sure I have much of a choice.

I still have no idea how the SI alternator ever charged without voltage at this wire (I'm assuming the tiny amount I was reading was just my cheapo voltmeter), but I never had a problem with the old setup. I should also note that ALL of the wires at the two ignition switch connectors were cut at some time a few inches from the connectors - why this was ever done is beyond me, perhaps the car was stolen at some time in it's history and the thief wasn't smart enough to know which ones to cut. I can't think of any other reason someone would snip the wires at that location. Either way, I've got some fun in store in order to fix this.

Gotta love hackers

I can't locate my own cheapo voltmeter as its in the garage buried somewhere, I didn't organize much since moving in in the late fall. I did check the wiring and its as I remembered, I removed the SI to CS adapter harness, used a factory plug and wiring from a CS alternator, spliced it into the Monte wiring and added a resister to the brown wire....probably doesn't help at this point but I thought I'd share. Do you have a spare alternator or know anyone local with the same kind on their car? As said previously, some alternators work differently than others as far as resistors, etc.