Cadillac electrical issue?


Asked by Dec 22, 2013 at 09:46 PM about the 1998 Cadillac Seville STS FWD

Question type: Maintenance & Repair

1998 Cadillac Seville Sts.
Alternator on the car went bad, Had the alternator replaced, then I got a voltage reading
of 16.5 ( too high ) I took the car back to the mechanic and They did a rebuild on the
alternator... Now. For two years 98/99 They put a Thermistor on the hot wire from the
battery ( located under the back seat ) I unplugged it not knowing what it was and the
voltage went down, however the power is all over the place now. Shifts between 13.5
and 15.5.  Randomly things stop working I.e rear defrost, gas gauge, sunroof, power
locks, gas cap, trunk while others still work... power windows, front defrost dash lights.
Thought maybe this was a fuse issue? So Narrowing it down to Voltage regulator,
Thermistor, random bad wire. Everyone seems stumped over this. One person said to
attach a 1600 ohm resistor to where the thermistor was and that would correct the
problem, I haven't tried this yet, don't even know how to go about connecting the

23 Answers

okay....this is like brand-new to me but this is what the internet says~The Battery Temperature Sensor is a thermistor placed in the battery cable very near the battery, under the rear seat. It was used in only a few model years. If the battery charging rate is too high it signals the voltage regulator to ramp down charging amperage, thus lowering battery temperature. The Intake Air Temperature sensor is a thermistor placed in either (depending on model/year) the intake duct near the filter box or at the edge of the bore of the separate MAF and has nothing to do with the battery charging sensing system. Transmission Temperature Sensor - that thermistor which turns fans to FAST at transmission fluid temps of 305 degrees. if the backseat battery is cookin', we don't wan't our cousin harry to have his butt fried~...that's why they limit the power goin' to the battery...and yes a 1600 ohm (seems a bit high) probably will do~....agreed~


Certain year Cadillac cars have a weird charging system setup, sort of a "charge on-demand" thing, and as a result I have seen a lot of unnecessary alternator replacements from Techs who didn't know this because the battery/starter/alternator test equipment would fail the alternator for low output because the ECM had cycled it off. I'm pretty sure the voltage regulator is integral to the alternator on this car, so it's possible that the alternator was not rebuilt correctly or the voltage regulator on it is bad. I would definitely suspect either that, or the thermistor in the cable. Were you having issues with the car before the alternator was replaced, or did someone tell you your alternator was about to sh_t the bed?

3 people found this helpful.

The thing that's not making sense to me.... and i understand the thermistor use... althought I think that's just caddy making things more difficult than they need to be.... but what's not making sense is everything that's going out now... the volts are all over the place, things not working... The thermistor tells the alternator "hey battery is cold, going to go low send more juice" I'm wondering if since I took that thing off the alternators just spouting off everywhere and blowing my fuses since there's nothing telling it what to send? I think that makes sense... The only thing I can think of is the voltage regulator but with the different alternator and that one being rebuilt all in the same week, what's the chances of them screwing it up twice? Can I get an external regulator?

2 people found this helpful.

Says everything done uptop, haven't done anything else as of yet

2 people found this helpful.

Okay....this is bullshit...cannot find a replacement "thermistor" for the the back seat battery getttin' all kinds of HOT? I simply would not worry about this....someone is simply tryin' to get money out of you~


backseat isn't getting hot, and they discontinued that part, wont find it unless i go pull on off another 98/99 caddy

1 people found this helpful.

it doesn't really "regulate" the temp of the battery so much as tells the alternator how much juice to send based off the temp of the battery. I know that's confusing. It was set up to limit the power sent and keep your battery from overcooking.

2 people found this helpful.

the alternator is a ONE WIRE affair...the voltage regulator is built in already...perhaps with the two batteries it gets kinda compicated...and yes the thermistor must be bulit into the special battery cable...that's why I cannot find it anywhere ~

1 people found this helpful.

good idea about goin' to the pickNpull...forgot about that place~

1 people found this helpful. seat-negative-battery-ground-cable-/360807669595? pt=Motors_Car_Truck_Parts_Accessories&fits=Year%3A1998%7CMake% 3ACadillac%7CModel%3ASeville%7CSubmodel%3ASTS&hash=item5401 d01f5b&vxp=mtr

5 people found this helpful.

says NOTHING about having a resistor/thermistor built in....perhaps it's a fallacy~


Two batteries? Never seen an STS with two batteries... Did they rebuilt the same alternator that they replaced your OEM one with? I'm wondering if they installed the wrong part, or the part was defective and the rebuild job they did didn't include replacing the voltage regulator. That's the only thing I can think of that makes sense to me. I've worked on these cars before and I know that it's common for a tester to FAIL an alternator because the output reads under 13 volts

1 people found this helpful.

Either way though, you need to plug back in whatever you unplugged because your whole electrical system is set up for a cycling-output alternator and with that thermistor unplugged, who knows how it's going to react and it's very possible that it will start popping fuses and overheating wires all over the place...


Hate that I can't edit previous posts, but here's what I would do. Leave the wire unplugged, take it back to whoever did the work and have them pull the alternator & replace it with a genuine OE part from a dealership, or like an AC Delco part, then plug the thermistor back in, and go from there.


my 1998 caddy is dong the same exact thing

1 people found this helpful.

nightmare .. buying alternators for nothing .. no one can figure it out

Joey...supposed to be a "one wire" alternator...possibly one goes to the instrument panel...for warning light...perhaps a three wire connector on that...simple...there are diagrams for this....just do a google search~

1 people found this helpful.

I have 95 olds aurora same as riviera. Same problem .new alternator new batt still discharges batt bought the service manual checked system per trouble shooting. Shart the only possyble problem is thermistor wire runs all the way straight to alt pin s pin l goes to pcm you have to check wires for shorts open wires. And voltages buying new thermistor on ebay dont bother with auto part store none carry it maybe dealer


I have 97 sls Seville alternator went bad put new one in and it went bad instantly why

1 people found this helpful.

Am un Cadillac Seville si nu gasesc bujia nu pot sa-mi dau seama undei ,ma poate ajuta cineva?


Can anyone tell me how I change the alternator out of my Cadillac Seville? Don't have the money to take to shop and can't figure it out !!!

1 people found this helpful.

I crunk my 1997 Cadillac Seville SLS up I unplug the positive side on the battery my car was still running but when I cut it off it won't crank back up I bought the battery from Walmart do you know what it is my AC compressor went out also does that have anything to do with me having to jump my car off the battery voltage is good it won't start back up

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