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1997 Seville STS, 2000 Seville STS
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Discussion Starter #1
I am the proud owner (or sucker) of a Red/shale 2000 STS with 140K on her. It has a couple of issues (rear windows being one) that I will get to eventually but the one I need to start with is the battery is not being charged. There is no B1911 code like I get on my 97 STS when the battery won't charge and the red battery symbol on the dash does not come on other than during the 2 or 3 seconds all the lights come on after starting the car. Alternator is new (1000 buck water cooled Delco one) replaced by the guy I got it from a short time ago (like 2 or 3 weeks ago) along with a new battery. Dash display says "BATTERY VOLTAGE 11.8V OK" like the car thinks everything is fine but the volts are really that low. He took it to a garage and they told him it was the "computer" that was bad, hence the reason he dumped it. I assume the output driver in the ECM for flashing the feild in the alternator is burned out and I don't mind replacing the ECM if thats what it is, but is there anything else I can check before I head down that route. Can I put a jumper from the positive terminal cable to the "F" (or "I") terminal wire on the alternator to see if it will charge without frying anything, that way at least I know the issue is between the alternator and the ECM. It may be the wire, or it may be the ECM itself, but I can check the wire with an ohm meter when I start fooling with it. Got to get rid of at least one of my 97's before I worry about this one. At least I don't have to do HGs on this one (yet):D.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Curious, I was under the impression the 2000+ alternator is not water cooled. Anybody know when the change came ???

Pull the rear seat cushion - push back, lift - and disconnect the seat heater connector on the passenger side. Check the battery cables, and the bolt which secures the ground cable to the weld stud in the floor pan. If necessary, pull the bolt and wire brush the area.

You have a very expensive PCM, not an ECM, and it's programmed specifically for your car and its particular VIN. Entirely possible that the alternator connector or wiring is bad - it won't be the first time.
 

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2016 Honda Accord LX. Previous: 2004 Deville, 2000 STS
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The change came in 2001 i believe; my 2000 Seville brochure says the car has a "water cooled alternator". On my car there is also a hose which looks like it's running down to the alternator. Not sure if that has anything to do with it though.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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71,110 Posts
You're correct - the RockAuto catalog shows the change came at the end of the 2000 run. GM learned from that mistake.
 

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1997 Seville STS, 2000 Seville STS
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1,694 Posts
Discussion Starter #5
I'm not worried about getting a new ECM, there are a few places on ebay with them and at least on of them will program it for the VIN. I've also found a place in NY city that will program the VIN and reflash one you send them for something like 55 bucks plus shipping. I just find it funny that I'm not getting the 1911 DTC, and the PCM/ECM did not show up in the module list that comes up after all the DTCs are displayed. Being its the ECM maybe it never does. Everything else seems to work OK on the car, just 2 current codes ABS C1242 and one MSM some thing.

Oh, my 2000 Deville had a water cooled alternator as well. That one is gone now as of this morning, selling it financed this one with some left over to pay off credit cards.
 

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1992 STS / 2005 MB G500 / 2003 STS / 2006 XLR-V
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11,694 Posts
Water cooled alternator appears to have been for '99 and 2000 only. My '98s did not have it.

Like Ranger has said before... Can not IMAGINE what the logic is behind cooling a damn alternator with HOT engine coolant... :hmm: Not to mention it is another place for leaks.
 

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1997 Seville STS, 2000 Seville STS
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Discussion Starter #9
Its not the alternator, its allegedly the output circuit from the ECM that supplies power to the field windings in the alternator. I haven't look at it at all for this specific issue yet, I checked it out (he already told me the ECM needs to be replaced per the GM mechanic) for general conditions, bought it, drove it to my parents house where it will sit until I get rid of at least one of my 97 STS's.
 

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1994 Cadillac Eldorado Touring Coupe
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821 Posts
It's the alternator more than likely.
I've never heard of some crazy part on the ECM fail that makes the voltage not read. (other than maybe a broken wire.)
One other thing to watch out for - the guy is telling you to replace an ECM! These cars have PCMs!
My money is on the alternator or wiring near it being bad.
 

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1997 Seville STS, 2000 Seville STS
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Discussion Starter #12
The Alternator was replaced by one shop right near where the owner lived, they work on foreign cars so after the, brand new, from GM $1000 water cooled alternator, was checked out and put in and it still didn't charge the shop took it to a GM specialist who diagnosed the bad ECM. I don't know how he did it, TechII, trouble shooting, divine intervention or WAG (Wild [email protected] Guess). I do know the ECM sends power to flash the field of the alternator thru what used to be called quad drivers (essentially a transistorized relay contact) and I supposed a short in that circuit could burn out that circuit. The previous owner called it a "computer" ECM is my term. Of course theres always a chance there is a bad wire somewhere between the alternator and the ECM, or that weird little thermister that is in the wire between the alternator stator and the battery is bad, I haven't looked into it at all. I may go over towards my parents house later this week and if I do, I'll take my voltmeter and a couple of lenghts of wire to do some jumpering to see whats up. The ECM does supply the voltage to flash the field on the alternator thru the L terminal (small red wire going to alternator connector)and monitors the presence of that voltage thru the F terminal (small grey wire in same terminal). This is what is supposed to turn on the battery light on the IPC and the warning message on the DIC. The funny thing is that I did not notice the red battery light on the dash, not does it have any current DTCs associated with the alternator not charging, like P1633 or P1634. There may be more issues with either the ECM or the wiring in the car, because I know the A/C is empty (they removed the radiator and condenser to get the WC alternator into the car) yet it doesn't report the low pressure condition either. But at the moment I'm not complaining since I got it for less than 2K and it runs and drives fine, other than not charging the battery. I've already arranged to pick up a new ECM from another 2000 STS for next to nothing so I'll send it out and get it reflashed to my VIN and slap it in and see what happens once it comes back. I'll figure it out eventually.
 

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1997 Seville STS, 2000 Seville STS
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Discussion Starter #13
Little bit more info, went over to check out the car, but couldn't reach the connector on the alternator without getting in from underneath and I was in work clothes so that was out. I pulled the DIM 10 Amp fuse (Fuse 38) in the rear fuse panel, this is the one that feeds the D terminal on the alternator, on a 98 this is the line that goes thru the thermistor between the battery and the alternator, but I don't think the 2000 has one. As soon as the fuse was out the instrument lamps on the dash came on, I got the "service electrical system" message on the DIC, and a "battery Voltage High" message. Battery voltage did indeed increase to 15V, so I now know that the alternator does indeed work. If I put the fuse back in everything went back to the way it was, both DIC messages went away, and battery voltage went back down to around 12V. Voltage is the same from the alternator output terminal all the way back to the battery terminals. I need to figure out what the lead from the DIM circuit does, and how this would allow the alternator to go to full voltage output.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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IF the system has a thermistor in that circuit, that would be used to control sensed battery voltage as some sort of charging voltage/current control. IF a resistor or thermistor is passing incorrect voltages, it's possible that it would limit or raise alternator sensing voltage and therefore alternator output. You pull the fuse and the sensed voltage goes to zero, telling the alternator to supply full voltage/amperage. If the engine had been running at something higher than idle, there's a real possibility of cranking out some damaging voltages. An alternator will put out some impressive AC power without regulator control............
 

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1997 Seville STS, 2000 Seville STS
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Discussion Starter #15
Yes that circuit appears to be the voltage sensing circuit, but if I truely have a problem with my PCM/ECM circuit (what the PO was told by mechanic who troubleshot the problem) which either supplies power to the field windings, or a ground to that circuit to energize the field windings, how is the alternator putting out any kind of voltage? My battery light does illuminate if I turn the key to run but don't start the car, but it stays off when the engine is running. On my 97 there is only one connection to the PCM for control of the field wiring (F terminal) and the warning light is operated off the same circuit as a feedback to the IPC (L terminal), the voltage sensing circuit is tapped of the BAT terminalo on the alternator internally. On the 2000 everything seems to be external to the alternator. The sensing circuit is tapped off of that DIM circuit, while the F and L terminal wiring goes directly to the PCM. The DIM does not appear to provide any control back to the alternator, that appears to be done by the voltage on the wire going to the D terminal on the alternator, The DIM voltage sence input is "T" tapped off of this wire and that appears to be how the battery light is turned on, when the voltage gets below a certain value. Yet the light won't come on at 11.8V (displayed value on the DIC while the car is running).

The only two current codes I have on the car are C1246 (need to replace my brakes), and M1845 (Drivers seat Lumbar Switch). I guess I need to Figure out how the regulator gets its inputs and outputs and if a low voltage input on the sensing circuit somehow overrides the PCM control input to the F terminal.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Don't know if this will help - it's from my 2002.
 

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1997 Seville STS, 2000 Seville STS
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Discussion Starter #18
No final outcome yet, still playing with it so I don't yank a perfectly good ECM when its really something else. My 2000 schematic looks about the same as the 2002 except the B and C wires go directly to the ECM from the alternator. B terminal is the L Terminal Output, and C is the Generator F Terminal Input. The battery trouble symbol comes on in the IPC if you turn the car on but don't start it, or if you pull the 10A DIM fuse 38 in the rear seat fuse panel. but it does not come on if the car is running. When the car is running the alternator does not put out any power, unless you pull fuse 38 and then it puts out 14V at idle, the battery light comes on, the "Service Charging System Message comes up, along with Battery Not Charging, and Battery Voltage high 16.5V. A volt meter on either the battery terminals, or the positive bus bar under the hood, and the negative jumpering terminal on the right shock tower both produce an actual voltage of about 14 to 14.4 volts. Apparently the alternator has some method of self exciting itself it it sense voltage goes to 0 but I can't find a functional description of how the voltage regulator actually works.

Next I pulled the 3 wire connector off of the alternator, and I want to personnally thank the engineer that put that connector on the back rear corner of the alternator at about the 4 oclock position and jammed it up against the top of the air conditioner compressor. With the key on I measured 12V on wire D above coming from the DIM circuit so that circuit is intact. Terminal C (the F terminal)measures 0volts, and teminal B (the L terminal) measures about 5 Volts. Now I have to figure out what this means. I think it means that there is no power coming down the F wire to flash my field in the generator, but the descriptions provided about the generator F terminal input, and the Terminal L outout names on my circuit diagram are confusing me. Next step it to disconnect the ECM and chack the continuity between the ECM pins and the generator terminals. Couldn't do it today because I didn't have a 35 Torx wrench to pull the air filter box out.

Went over to my parents where the car resides this weekend,
 

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1997 Seville STS, 2000 Seville STS
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Discussion Starter #19
Everything, I'm reading seems to indicate that the external wiring is operating as it should. The PCM sends 5V to the generator thru the L terminal to turn on the generator (I have this), the F terminal is a signal back to the PCM so the pcm can control engine speed and alternator load (can't test this without a breakout box of some kind), S terminal sences battery voltage (it does). I think I'm going to have to pull the alternator (and the radiaotor and condensor) and get it tested, even though its brand new.
 

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1997 Seville STS, 2000 Seville STS
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Discussion Starter #20
Anybody know what the difference is between a 98/99 Seville Alternator and a 2000 alternator? GM has two part numbers 19152137 (or 10464581) for a 98/99 and 10464434 for a 2000. All are water cooled (I think). The exterior electrical connections seem to be the same with the exception of the thermister on the positive lead of the voltage sense circuit that the 98/99's have (2000s don't). GM switched PCMs going into 2000. My 98 service manual says that the voltage from the PCM to the alternator should be 10V or greater, but the 2000 service manual says 5V (it seems to vary though depending on where you look) . I'm thinking that this may be my problem, someone may have put a 98/99 alternator in the car and the regulator is not getting the correct voltage from the ECM. Do these things have part numbers stamped on them like the old alternator used to?
 
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