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99 deville, 99 STS, both White
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Discussion Starter #1
Hi All, I am narrowing down the issues with this bugger. Since I did the HG on this car I have been working thru all the gremlins that have arose from sitting for probably 15 years in the shade on dirt. So there has been lots of corrosion and rust. So I bought a new alternator 2 years ago when I had hoped to do the HG job and get the car right on the road, well that did not happen so fast forward 2 years plus and it has a new pure energy alternator and new auto craft type 79 battery. I do not think in the last 2 weeks of me trying to get this thing to pass inspection the alternator has worked, as the battery seemed to just get weaker and weaker.

I changed both left side hubs/bearings and took it for a drive on Saturday, hoping the service suspension warning would stay away, well it did for about 5 miles then it popped on again, I drove somewhat aggressively for a couple miles and then the charging system is not charging warning came on, it was dark so I kept the lights on low beam and turned the heater off, it was like 15 degrees out. I got all the way home and the car died just as I eased it into the garage, just died. so I put the trickle charger on it and got back on it last night, I tested the battery with the charger unhooked 12.4 volts, checked to ground same, at front fuse box same 12.4. So I started the car and turned on headlights on HB. at battery it dropped to 12.1 volts, same to ground, and at front fuse block. Alternator must not be putting out. I checked DIM fuse position 38 in rear fuse block it was good. I then checked hot side of alternator connector to the starter, it was tight, so I unplugged the 4 wire connector to the alternator, turned key to run, and on B I got 11.13 V, 0.13V on C and 0 Volts on D. I checked the wires back 12 inches or so from the plug, no physical evidence of short or broke wire. Looks like no power getting to the alternator on D, that should be hot all the time right?

Does anyone know or have a picture of where the connection is on the wire running back to the Battery thermistor (sp) and what else can I look for in relation to no power to the D wire at alternator? TIA Bill
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,449 Posts
Hmmm............. You need the several charging/alternator wiring diagrams for THAT car. Take a look at a multi-year subscription to www.alldatadiy.com. It's the GM service manuals plus a LOT more.
 

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Registered
99 deville, 99 STS, both White
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86 Posts
Discussion Starter #3

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Registered
99 deville, 99 STS, both White
Joined
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86 Posts
Discussion Starter #4
Still looking for some guidance on where physically the hot wire from the Thermistor to the alternator is routed so I can try to find the break, or could the thermistor be bad? how do you test it and can you get a new one? TIA
 

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'98 STS (RIP @ 206,xxx miles)
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4,854 Posts
Still looking for some guidance on where physically the hot wire from the Thermistor to the alternator is routed so I can try to find the break, or could the thermistor be bad? how do you test it and can you get a new one? TIA
In your shoes, I would look elsewhere for your alternator solution. The thermistor circuit is only designed to fine tune alternator output voltage as a function of battery case temperature. The range of that fine tuning is limited to approximately 0.5 volts in my experience.

The fact that you appear to have zero alternator output voltage is not the result of a failed or faulty thermistor.
 

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99 deville, 99 STS, both White
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86 Posts
Discussion Starter #6
I found the issue, the red wire at the plug right by the battery positive terminal connection was corroded and broke off. fixed that and I have 12V all the way to the alternator. It seems to be charging although with the lights on high beam, the heater fan on high and the radio playing, the charging Volts read 11.6 OK, maybe cause the battery was quite low? I was holding the RPM's about 15-18 hundred. when I turned off all accessories in 2-3 mins it went up to 13.2 V so it is certainly charging.

On the wipers, the pulse board did not fix the wipers as the FSM indicated it would. Can someone tell me what pin I need to jump with 12V. to test if the motor works? wiper_Plug.gif

just to rule out the stalk switch

Thanks!
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,449 Posts
FWIW, 13.2 volts is the setting that a "BatteryMinder" uses to keep an idle battery fully charged. It will NOT charge a car battery in use and under load - that takes 13.8 - 14.8 volts and quite a bit of initial amperage. You should see over 14 volts in your DIC any time the engine is running.

Give it a couple of days to see if an excessively discharged battery comes back to life - if not, it's either new battery time, and if the voltage does not then rise above 14, it's alternator/regulator/charging circuit diagnostic time.
 

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99 deville, 99 STS, both White
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Discussion Starter #8
Will do Sub. thanks for the advise, I started a new thread on the wiper issue.
 
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