[Stuckinda60s]

My wife's van, a 2006 Pontiac Montana SV6 AWD, started giving me some strange symptoms, today.

We both have the flu, and I took her over to the doctor's and waited outside for her. I sat and listened to the radio for close to an hour while I waited for her. When I went to start it, the battery was too low. It's the original battery, but hasn't been giving any problems. I always understood that the computer would turn stuff off if the battery got too low, but apparently that isn't true.

Anyway I called for a jump and it started right up. We drove about 15 miles and when I stopped for a light, the fan was running but the temp gauge was very low and the Check Engine light wasn't on. When I got a chance, I parked and checked things out. The engine was cool but both fans were running. I had thought that maybe the coolant was low and the sensor wasn't getting a good reading because it wasn't in contact with it, but that wasn't true. I tried to pull the fuses for the fans but they didn't want to come out, so I unplugged the harness to the fans.

I drove home with the fans disconnected, through traffic in town, and thenpulling a pretty good-sized mountain where the van downshifted all the way to second gear for a short period. I had about a 5-miile run down the other side and then it was relatively level all the way home. The gauge never moved, up the mountain and down and was still at the bottom when I got home. It ran great and showed no signs of overheating when I checked it at home.

The coolant level is good, and the engine runs cool. The gauge continues to read at the bottom and, if I hook the fans back up, they'll run continuously as soon as I start the engine.

I'm wondering if it's possible that the troubles are related and, if so, how? If the coolant temp is low, the fans should never run. If the relay(s) is/are bad, the fans shouldn't run. If the gauge is bad, it shouldn't effect the fans, right? Is it possible there's a problem with the computer? What about a bad ground path?

Is it possible I'm in a fail-safe mode? I've got no check engine light. I'm just a little perplexed.

It turns out that the battery is on the way out, and I'll get one when I can work on the thing without having a coughing fit. I can't see how that would have any effect on the situation, though.

Anyone got any suggestions or access to a process tree?

[wytnyt]

replace the battery and go from there,a battery can start a car ,yet starve the car with enough current to run everything.i had a dodge that would crank and start fine but guages were flaky and once the engine warmed up,the truck rpm would keep dropping the longer i drove it,engine woulddie at idle and the battery fixed it.and no the computer will not shut the radio down if current gets low.

[Simple Man]

My wife's '05 Mustang would start, but nothing like lights, radio, etc, would work. Bad battery.

[Stuckinda60s]

Originally Posted by wytnyt

replace the battery and go from there,a battery can start a car ,yet starve the car with enough current to run everything.i had a dodge that would crank and start fine but guages were flaky and once the engine warmed up,the truck rpm would keep dropping the longer i drove it,engine woulddie at idle and the battery fixed it.and no the computer will not shut the radio down if current gets low.

Her van's got 110 volt outlets. They will shut down at a set point. Any lights left on will turn off after a certain length of time, also. All my GM vehicles, since at least 2000 will do that. I thought the accessories were idiot-proof, as well.

Everything works fine, with the exception of the gauge and the fans. The battery charges fine, but loses voltage , slowly if parked. It sat from Saturday till Monday and started fine. It only gave a problem when I put the radio load on it. I'm not real confident, but I'll get a battery and update this thread as to how it acts afterward.

Thanks for the posts, guys.

[wytnyt]

true many vehicles will shut things down if left on but the reason isnt because of low voltage but triggered by an amount of being on without an interruption like opening a door which will reset the shut off time
a ground can also cause your problem but going by what you said about the battery going dead so easily makes me think its lost its reserve capacity,newer cars with so much electronics rely alot on the battery when the rpm is low such as idling.,unlike older cars where once started the battery isnt needed again till the next startup.

[Bill Meyer]

I think this is a GM problem of that year +/-. I have an 06 Cadillac and twice now the temp guage has gone to zero/cold and both big fans come on. My car also has a digital display that says "engine hot A/C off". I checked on the internet for these symtoms and found many GM owners with this exact problem. The dealers typically replaced the thermostat and the problem disappeared. I just disconnected the battery cable and it corrected itself.
By the way, the engine isn't hot at all and it performs just fine. If the thermostat was stuck open the car would run cool, my heater worked just fine. If the thermostat was stuck closed, the car would indeed run hot-but it's not.
Once you get your new battery in I think your problem will go away......Bill....

[Stuckinda60s]

Thanks, Bill. That's pretty much what I was wondering was true or not. I thought about disconnecting the battery and letting every thing reset, but I'll save that chore for when I replace it. It's not a real easy job. I just wanted to be prepared for when I can take of everything.

With my wife being sick, the van's getting a break right now and not being used. Ordinarily, it never rests. The battery has seen more starts and stops than a Nascar season, it doesn't owe me anything.

[skipp65]

I'd buy a good battery from advance or auto zone,they will install it for free.Then you wont have to mess with it.

[John V.]

Originally Posted by Bill Meyer

I think this is a GM problem of that year +/-. I have an 06 Cadillac and twice now the temp guage has gone to zero/cold and both big fans come on. My car also has a digital display that says "engine hot A/C off". I checked on the internet for these symtoms and found many GM owners with this exact problem. The dealers typically replaced the thermostat and the problem disappeared. I just disconnected the battery cable and it corrected itself.
By the way, the engine isn't hot at all and it performs just fine. If the thermostat was stuck open the car would run cool, my heater worked just fine. If the thermostat was stuck closed, the car would indeed run hot-but it's not.
Once you get your new battery in I think your problem will go away......Bill....

Interesting.

'04 GP GTP. Several weeks ago, I noticed my temp gauge reading stone cold while driving around.

Few years ago, I had a mouse chew up the wire from the sender. I repaired it myself. Has been fine since.

When it read stone cold, I assumed the splice failed. I jiggled the wire, tried to make it respond but nothing. I don't recall the electric fan running but wasn't paying attention to it either. I tried multiple times to restart the car. No change. This gauge will spin all the way around during start up then settle back to position. It did so on that day, but each time returned to the stone cold stop, no movement/reading.

Anyway, I expected to have to unwrap the harness to get to my splice. But before I did, the next day, the temp gauge was working normal again.

It reminded me that one time last winter, I drove the car for a few hours. The temp gauge had a reading above stone cold, but quite a bit lower than typical. That time I wasn't getting much heat either. I remember trying to mess with the HVAC to see if I could get the temp up (I think I musta turned it off hoping the engine would warm up more). It was cold out, but north Fla cold, maybe in the 40s. I wonder if the electric fan was stuck on then. Happened in the morning. Return drive that afternoon seemed normal and hasn't happened that I've noticed since (except for the day it read stone cold).

Wonder if thermostat is culprit.

My '99 Sunfire overheated one day. Son was driving it home from school. He didn't notice the gauge until the check engine light lit. When I got to him, the coolant tank was empty, I refilled it, drove it the rest of the way home. Kept it 3 more years and it never acted up again, coolant level never changed. I always suspected the thermostat must have stuck closed but never did anything about it.

Some things just can't be explained.

Battery was dying on the '03 Wrangler last spring. I remember the clock would not keep time overnight. Might have been some other electrical gremlins that had me fearing the worst as I recall. But it would start fine. Suspected the battery because my son had had to get jumped a few weeks prior. I first worried the jump had fried something(s). Replaced the battery and everything worked normal again.

[geeteeohguy]

Agreed. Replace the battery and go from there.

[Stuckinda60s]

Well, I neglected to post what happened with my problem. Sorry.

The battery would slowly drop off after a charge. I let it sit for a few days and it was down to 11.6-volts. I charged it before I started it and the problem with the fans and temp gauge had cleared. Changed out the battery and all's been gold ever since.