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Post by taper on Nov 11, 2012 12:58:07 GMT -6
Hi guys, Could someone please tell me the correct ohm value for a working thermistor? I've read it's 1.68 ohms, but would like verification. Has anyone found a source for a battery thermistor yet? I've searched the web and only found not in stock everywhere. Any alternatives such as wiring in a resistor from radio shack or something?
Thanks in advance... Mike in KC
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bobsblue95
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Scars of pleasure, scars of pain. Atmospheric changes make you sensitive again.
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Post by bobsblue95 on Nov 12, 2012 12:22:58 GMT -6
More like 1.68 Kohms, at approximately 70*F. Hold your thumb on it and watch the value... uh... drop I think. The thermistor is very unlikely to fail. Start by checking the wires on both sides of it's connector. That's where mine looked fine but when I tugged on it, one wire pulled right out. Eliminated the connector, soldered and heat-shrinked the wires and haven't had any problems with it since. Good luck!
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Post by taper on Nov 13, 2012 18:23:49 GMT -6
Thanks for the reply. I'll look for the 1.68 K ....then check the wires. I have a "check charge system " warning and the red battery icon lit up. Replace battery last year with appropriate replacement (new) replaced alt. the other day (pita) and the voltage reads between 13.8 to 14.2, the batt. reads 12.5 - 12.6 When replacing the alt. the ground wire between the support and frame looked fine at both ends, as does the wires to the batt itself. The small signal wires to the alt. looked fine also.... not much left to check except the thermistor....and if anyone else would like to chime in that had /has the exact situation...I'm all ears.
Thanks, Mike
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bobsblue95
Super Moderator
Scars of pleasure, scars of pain. Atmospheric changes make you sensitive again.
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Post by bobsblue95 on Nov 13, 2012 20:23:53 GMT -6
For the record, I was also getting the check charging system and battery light, and the DIC showing in the high 12 to low 14 range while running. Once I repaired the thermistor wires, the warnings went away and the DIC reading went up to 14-15 range ( and they all seem to read about 3/4 volt higher than a volt meter will read.)
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Post by taper on Nov 14, 2012 19:30:03 GMT -6
well....I cant seem to find anything wrong anywhere, yet the voltage light remains on, and check charging system dings at me every now and then. To recap: New Batt (last year) New Alt (last week) all grounds are fine thermistor read 1.74K Ohms (50 degrees outside) thermistor wires intact Alt wires intact (signal wires) between 13.9 and 14.2 volts measured at battery term with my voltmeter, and engine running and lights on 12.6 measured at the batt ignition off
Im starting to think its the PCM ...I read the FSM and that's the last step of the diagnostic puzzle. I believe it's the PCM's job to monitor voltages...I may be wrong there.
I also need to add that one of the instrument panel dimmer modules is out (the one that controls the lights on the PRNDL indicator & the door control lights. (window switches etc.) I wouldn't think this would have anything to do with the charging circuit, but who knows? Maybe another wire broke inside of the door harness where it flexes shorting something? ( I had to splice a few wires last year that controlled the power windows...as they broke in half) Also, one fog lamp out...could it be GM made the Check charging system nag you to change a bulb?
Anyone else care to shout out?
Mike
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Post by sall on Nov 14, 2012 19:59:15 GMT -6
IIRC there is a list of steps to check if the battery light stays illuminated at all times. I'll see what I can find.
Often a bulb out would render cruise control inop but not on Auroras.IIRC there is a list of steps to check if the battery light stays illuminated at all times. I'll see what I can find.Auroras
Usually a bulb out would render cruise control inop but not on any Aurora. Never heard of cutting the charging system.
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bobsblue95
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Scars of pleasure, scars of pain. Atmospheric changes make you sensitive again.
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Post by bobsblue95 on Nov 15, 2012 7:32:16 GMT -6
I can tell you that the PCM doesn't control the battery light. It's a simple alternator driven dummy light. Your voltage numbers are right in line, so it's time to follow the diagnostic charts...
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Post by sall on Nov 15, 2012 7:46:33 GMT -6
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Post by taper on Nov 15, 2012 16:09:15 GMT -6
Thanks for the checklist. That's straight out of the FSM I've been following.
Is step 8 the same thing as checking the resistance directly at the thermistor like I've done? (to get my 1.74 K reading)or, do I need to do it by the book?
Step 11 leads me to believe the PCM is involved....
How do I do steps 13 and 15? Those 2 circuits are the signal wires coming off of the alternator connector. Do I set a Ohm meter on each to check for open or shorted condition? Or, do I set a volt meter to check the voltage? I'm confused on those steps. If someone could please be kind enough to give me a step by step direction to go with...I'd appreciate it.
As a last resort, step 17 recommends replacing the PCM. Does one have to have it flashed? I've seen them on Ebay for as little as 49 bucks....
And Sall.....how do you get the FSM in a PDF file...thats very handy.
Thanks again for all the help guys...
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yaygull
Aurora Watcher
1996 Aurora - Pearl White
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Post by yaygull on Nov 15, 2012 21:34:19 GMT -6
I had the same "check charge system" message when I bought my car. It was really annoying, so I took the thermistor off completely. That didn't solve the problem immediately, but the problem did seem to go away on its own before long. I put the thermistor back on a couple of months ago and haven't seen the message since.
If it's any help, I only got the message during the really really hot months of summer, and I seem to remember having to fix the vent tube in the battery compartment. Hope either of those tidbits help in some way.
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Post by brody2be on Nov 17, 2012 10:08:51 GMT -6
as of 11/17/2012 there is one on e-bay for $31.99
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Post by taper on Nov 17, 2012 16:17:28 GMT -6
Well....thanks for the replies. I should mention this is my girlfriends car....I only get to see her maybe once or twice a week. The car is always starts for her...but that light on freaks her out. I hate to think that every time I get to see her...I spend all my time trying to figure out the car situation. It's getting frustrating. But next weekend...I am going down the checklist....item by item...till I find it....even if it means swapping pcm's. I really don't think its the thermistor anymore....but I didn't check it "by the book"....rather, I just measured the resistance across the 2 terminals. (1.74 K Ohms) The wiring connector was sound...I tugged pretty hard on all the wires, I am going to try the unhook all the grounds next...sand the ends or wire brush them or something, the re-attach. Also, going to check the PCM connection. If and when I figure this out...I will be sure to post the results here in case some other unfortunate soul has to deal with this scenario. Keep those ideas coming...and thanks again.
Mike
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Post by galaxysilver on Nov 28, 2012 15:13:40 GMT -6
Where is the thermistor anyways? I can't seem to find it in the appendix of my gm manuals. I am having check charge system issues right now, and need to check this. I already ordered generator and new battery. The battery cooked from overheating/overchargeing from bad generator. DIM fuse fine and should i check that ground under the fuse box in the engine compartment? It is a 2001 3.5
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Post by sall on Nov 28, 2012 15:24:01 GMT -6
It's referred to as battery temperature sensor in the FSM. It is located on the positive battery cable near the battery. I do not believe the 2G has one.
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Post by galaxysilver on Nov 28, 2012 15:41:36 GMT -6
Ah!!! thank you sall. Would a thermistor have saved my battery cooking from an overcharge?
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bobsblue95
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Scars of pleasure, scars of pain. Atmospheric changes make you sensitive again.
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Post by bobsblue95 on Nov 28, 2012 15:58:05 GMT -6
Ah!!! thank you sall. Would a thermistor have saved my battery cooking from an overcharge? Only if the PCM was programmed to monitor it and control the charging. If the 2G doesn't have one, you can't just put one there and expect it to work. The pcm monitors the positive cable temp and turns the alternator output off if it's getting hot.
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Post by taper on Nov 28, 2012 18:34:59 GMT -6
From what I gather, the thermister is much like a thermostat. It reads the temperature of the battery and/or cable and relays that info to the generator/alternator to tell it to "lighten up" if it senses that battery is getting too hot.
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Post by bobozr on Jan 10, 2017 21:57:02 GMT -6
I am having some of the same problems with my son's 98 Aurora. The Alternator went bad. I had it rebuilt. re installed and then it was putting out 18.1 volts. Removed it again and had another new regulator installed. This regulator was supposedly designed to work with the "Thermistor." Re installed and it is still doing the same thing. I think my Thermistor is bad. Taking it out of the system, the alternator will not charge at all. This is the Northstar 4.0 so you know that the removal and reinstall of the Alternator is a PITA. I am getting better at it though. These thermistors are no longer available from GM or any aftermarket supplier that I can find. If anyone has any ideas or work-arounds I would really appreciate it.
bob
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Post by sall on Jan 11, 2017 19:50:18 GMT -6
I am having some of the same problems with my son's 98 Aurora. The Alternator went bad. I had it rebuilt. re installed and then it was putting out 18.1 volts. Removed it again and had another new regulator installed. This regulator was supposedly designed to work with the "Thermistor." Re installed and it is still doing the same thing. I think my Thermistor is bad. Taking it out of the system, the alternator will not charge at all. This is the Northstar 4.0 so you know that the removal and reinstall of the Alternator is a PITA. I am getting better at it though. These thermistors are no longer available from GM or any aftermarket supplier that I can find. If anyone has any ideas or work-arounds I would really appreciate it. bob Grab a resistor assortment or and try some values between 1.5 and 3k ohms. Your local hobby store will have them for cheap. If it proves to work I have a thermistor or two laying around. We can work something out.
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