Hi everyone,

I did the 88 alternator upgrade on my 87 V6, and I have a small (?) problem.

Occasionally, the alternator light comes on, and the voltage reading dips up a bit for a second or so. Looks like the alternator recognizes this and regulates the voltage down again.

Now my question is: is this normal? Did I make a mistake hooking it up, or is the alternator bad?
As for hooking it up, there are really only two wires to hook up except for the big power lead. And one of them is the lamp, which obviously works, the other would be the sense input. But that one is connected to battery a few inches from the alternator.

Any advice? Oh, the unit is a rebuilt ACDelco, I didn't want to risk a DOA... but maybe that's what I got after all...

Best regards,

Oliver

No this is not normal, and a spike in the system could be harmful to the car. I assume you installed a CS-130 or CS-144 alt? I know it was a CS series because you state you have an S and L pin.

There are two wires required for any CS style alternator; the large red wire that runs from the back of the plug (Pin S in diagram) to the lug on the alternator. This isn't really a "sense" feed, rather power to the armature during startup. Then the alternator needs an exciter wire (pin L in diagram "lamp") that runs to the "VOLTS" bulb inside the cabin. The resistor in the diagram is actually the resistance from the light bulb.



The '87 Fiero uses a second hot in run feed to power the alternator (seen below).



This wire comes in at terminal F in the first diagram, which is pinned "i" on your old alternator. The newer alternator does not need this input, and often times this lead will destroy or throw a newer alternator out of whack. I'm confused because you didn't mention this third wire, even though all 87 harnesses incorporate "I/F" wire. If this wire is hooked into the back of the alt, I recommend you snip the wire a few inches back and drive the car to see if the problem goes away. The newer alternator is self contained, and will be very happy to only see input from S and L. If you used a custom pigtail on your new alt., and only S and L are hooked into the alt. with no "I/F" wire, it would mean that the on board voltage regulator is acting weird and you should have the alt. tested or replaced. It's also possible that the "I/F" damaged it (if it's hooked up) and new alternator would also be at risk if you didn't remove the "I/F" wire after replacing the alt.

[This message has been edited by Emc209i (edited 03-15-2009).]

My 87 came with the SI alternator, which only has a two terminal connector for lamp and 12V. I cut off the old connector as described in another post, and connected L to the lamp and S to +12V from the old SI connector. The other two wires on the pigtail (P and I/F) are open.

BTW, I got the alternator from the Fiero Store, it is supposed to be the same unit as used on the 88 V6. I had considered hooking up I/F, but after going through the threads here, I had decided against it.

I must admit though, that I have not measured the voltage accurately, because I didn't have a DVM handy during my test drive (Who'd expect THAT kind of problem...) But if the lamp comes on, the alternator "notices" a problem as well I guess, no matter what the voltage is.

The ECM does not set a fault though, so I guess the voltage is not high enough for an ECM code.

[This message has been edited by fieroluke (edited 03-15-2009).]

Update:

I did a test drive this morning (to work ;-), and measured the voltage when it dipped high: 15.3 Volts. All other times it was 13.8 +/- 0.1 V.
The problem appeared after driving for about 2 miles, then the voltage stayed high. After another mile the voltage went to 13.7 again and stayed there for the remaining +10 miles, rock solid at 13.7V. Hmm. Is the problem gone now? We'll see. The alternator had been sitting in my (unheated) garage for a few months, maybe there was some corrosion inside that had to wear off?

We'll see... but if that's the case, I'm glad I didn't yank the alternator right out again to send it back...

I did a little research after you posted your morning find. I came across this reply to a similar incident:

quote Originally Posted by Jim_Lou @ Forums.off-road.com Two possibilities come to mind: 1 The regulator is bad. 2 The sense wire is disconnected or has high resistance - more likely in my opinion. In a stock installation the sense wire is usually a short red jumper from the output terminal to one of the two spade connectors on the alternator housing. It's supposed to tell the regulator what the system voltage is. If it's disconnected the regulator will tell the alternator to run wide open. A common modification is to run the sense wire to a spot as close electrically as possible to the battery. That tells the regulator what battery voltage is, which will be a little lower than the voltage at the output terminal. The other wire on a spade next to it provides voltage to bootstrap the alternator when it starts running. It will run to the warning light, if so equipped, and then to the ignition switch.

I remember you mentioned that your S terminal was wired to the battery several inches away. Could it be possible there is a poor or corroded connection? When I wired my custom alternator, I wired the S wire directly to the stud on the back of the alternator, that way it would have the most resolute and clear output signal from anywhere on the car. I suppose if there were an accessory or power option (such as the AC clutch or EGR solenoid) that is engaging or shorting, it could cause a system voltage drop, which could be screwing with your regulator settings. Might be worth a try. Hope this helps.

I had thought about the S-wire as well - what else could it be except for a bad regulator?
This afternoon the problem came back when I hit the accelerator and revved up the engine.
Really, there is no pattern to when the voltage goes high. I thought something was corroded inside the alt like a brush or something, and had to clean itself through use.
I'll measure resistance of the S-wire to battery tomorrow.

Thanks for your tips!

A brush would cause the alt to under charge. The regulator isn't supposed to allow anything above 14.8 volts past it. If it does, its because the regulator is purposefully allowing it (S wire), or it is malfunctioning. Try moving the S wire and see if that helps. If not, it wouldn't be a stretch to believe a rebuilt delco has a bad regulator.

Here's an update:

I measured voltage on the "Sense" line at the connector: steady battery voltage, no drops when pulling or otherwise mutilating the cable. So the connection seems solid.

The Helms manual (and other sources on the web) say that the CS130 can work in a two wire setup: Lamp and Battery. S, I/F and R are not required, and can be left open. So it should not make a difference whether or not Sense is hooked up, but it *is* hooked up and there is battery voltage on that terminal. When going through the troubleshooting tree in the Helms manual, the result is bad regulator or shorted rotor. In either case, the problem seems inside the alternator.

To make a long story short, I'll get a replacement and see if that cures the problem. If so, it will be the first DOA I have had going genuine (?) ACDelco.

Thanks everyone for their help.

-Oliver

I have a similar problem. But, my volt light does not come on with the ignition in the run position, car not running... Bulb is good and does flicker when accelerating along with a jolt in the charge gauge. but the battery will not charge. I have a rebuilt cs alternator. I stupidly exchanged it for my "working alternator when i did my 3.4 swap because I wanted a new "looking" one.

'ALL WIRES HAVE 0.0 OHM READING FROM THE ENGINE BAY TO THE DASH BULB AND FUSE BLOCK" I've read the 88 manual front and back practically. ( I have the "s" pin - red wire to the battery block, The "I/F" pin - brown w/wht stripe wire the dash gauge wiring cluster [which I believe goes to the fan fuse form the manual] , The "L" pin - solid brown wire to the dash gauge (TO THE BULB) and after the bulb it continues with the pink/blk stripe to the fuse block. There is a red solid wire after the fuse that continues somewhere. The gauge of the wire is a little bigger the the pink/blk stripe wire.

Would the theory work of not attaching the brown w/ wht strip wire? CS-130 -- 100 amp

I've torn the wiring harness out. Well mostly, tested all points through the engine bay of the car all the way to the gauge. all is 0.0 on the ohm reading. This is the solid brown wire. The brown w/ white strip is also a good connection from meter gauge from the engine bay to the dash wiring cluster where it connects to the wiring for the gauge pod. The pink w/ black stripe goes to the fuse block and is in good condition. With the key in the on position, car not running, (testing the fuse area front side) I get connection ground in the little fuse area (both sides - fuse out).

I just took the alt to Autozone to check.. and it passes.

Could the theory of not connecting the I/f pin be the culprit? Because of this new rebuilt?

Does the charging system go through the ECM at all? I remember when I finished my swap, I charged my battery for a day, because it sat for months, and saw the the volt light was faintly dim as it was being charged. Could I have shorted something in the computer? I have an 85 ECM 5 speed manual as a spare-- although I have an 88GT vin 9, Is it safe to use..... I got it for future turbo because of the built in knock sensor.

YES I'M STILL HAVING PROBLEMS for some who know.


ANY HELP IN THIS??? My next step is to put the top half of the engine back together (only way to get the wiring harness out and see if I have a volt light with NO I/F pin attached.... Any other pointers? Thanks for any help...

[This message has been edited by unboundmo (edited 10-23-2009).]

would a over charge from a regular battery charger ruin a ECM computer... Does the brown or brown w white strip wire go through the computer... Or even the pink w/ black stripe??? Would this be a cause for no volt light with the key in the run position, car not running?? It doesn't show this route in the thick 88 manual.. Am I missing something?//

(( There is a gray wire that I haven't traced from the gauge pod wiring cluster connection )) does this go to the computer?? I know the light tan one goes to the oil sending unit. Just haven't had time for the rest of the check

What else is there???????????

An 85 5 speed ECM would work in an 88 5 speed, same engine.. Right?

[This message has been edited by unboundmo (edited 10-24-2009).]

The Alternator on the Fiero is totally separate from the ECM, i.e. it does not control or diagnose it (on some newer ECMs the ECM does control the Alt, but not on the Fiero).

Could it be that you have a CS130 with a regulator for a newer ECM? Then it might not get activated at all. But for testing, did you disconnect the alt connector (with the battery disconnected) and turn on the lamp by grounding terminal L with the ignition on, engine off? The lamp should turn on. If it does, that circuit is ok.

Can you determine the part number of the <i>regulator</i> on your CS130?

Here's an update...

So I put the car back together from testing the wiring harness and all of the car. I exchanged the alternator with another rebuild from Napa, had them bench check it and it passes before I took it home, and it's installed. I turned the key to the on position and I'm still in the same boat. ((I did not start the car at this point)) Later after testing and buying the ignition switch mentioned later in this post, I did however go for a cruise and man this car purrs. 950 idle with no fluctuation. accelerates great with only 298 miles on the new motor. HP is starting to show itself. ( I do get a surge on my volt gauge as I accelerate from a stop position only - in the 15-16V range with a flicker of the volt light. ) It then act as if the alternator turns off at cruising. Battery still with no charging. This repeats after ever signal or stop sign.

• Battery test is good.. 550 cranking amp and it does charge.
• I've replaced the ignition switch.
• I have an new pigtail plug to the alternator
• I've done the "ground the L pin with the key in the on position and I "DO" get a volt light in the gauge cluster, from the 88 manual testing section.
• I have continuity from the alt pigtail to the dash gauge cluster. Every wire! Even to the fuse block
• I've tested current with a light meter and all S, F, L pins turn the meter light on. So that works.
• Voltage reading from the S pin is 12.49V, from the F pin is 12.15V, from the L pin is 12.15 as well - all with key in the on position. key off I only read current from the S pin
• nut lead from the alternator to battery block is good. 0.0ohm continuity. and has current plus volt reading of the battery (12.49V).

I've talked to Chevy and the Ontario California dealer has some of the Pontiac's mechanic techs from the closure as a rehire but who knows a Fiero when you need one. 90 dollar diagnostic and if that doesn't tell you, 100 or so after an hour. I've talked to West Coast Fiero, and in brain storming with Chris, he thinks it's the alt - ( as do I ). I'm afraid that the alt will pass the test from Napa though. I've also talked to Keith from my club that has a northstar himself and has done 30+ rebuild/swaps and is at a loss like me .

I'm thinking to bit the bullet and take it to the dealer ... Man if they mess up my new leather and suede interior / engine or whatever........^$%#$$@$&^*()

WHAT ELSE IS THERE? Sorry to steel the post with my troubles....