On Star draining the battery
 

A few days ago i went to drive to work but the truck wouldn't start. The battery appeared to be dead.
I had only used the car 8 hours before and no lights were left on and the car was left as i usually leave it.
The AA were called out and the mechanic said there was no drain on the battery and so the battery was faulty and needed to be replaced.
Although the mechanic said there was no drain comming from the car, when jump started the truck then left it for a while, the lights would go dim and it wouldn't start again.
I noticed that the OnStar button had been flashing red (not sure what this means as we don't have OnStar in the UK) and this was the only thing that had changed before the battery went dead.
So i pulled the fuse for the OnStar (located under the bonnet in the fuse box) and now the battery is fine and the truck starts first time every time.

Just thought i'd share this as although the AA didn't pick up the drain comming from the redundant OnStar activation, it was clearly the cause for the battery being flat.

Re: On Star draining the battery
 

I pulled the fuse on my Onstar awhile ago. Don't use it and I heard about the drain before.

Re: On Star draining the battery
 

OnStar is a VERY common source of battery drain on the H2 and I pulled my fuse as soon as the complimentary free OnStar service was completed! There's a picture of that fuse in a previous post or someone with good photography skills can post another.

Re: On Star draining the battery
 

I've always had some serious doubts about the onstar module draining battery. I've never once seen someone post actual data numbers on excessive amperage usage. Its a cell phone...and you have a battery 200x the size of whats in a cell phone. It doesn't put out any more transmitting power than a regular cell phone. No way its going to kill a healthy battery in a day or even a week.

When you jump start a car, there are all kinds of electronice operating at voltages below normal operating requirements. After your battery gets fully charged up, you should disconnect it- let it sit for 15-20 minutes then hook it back up. This allows the correct voltage for everything to fire up and go operational.

Re: On Star draining the battery
 

MUD that was my thoughts also, but it's hard to ignore.
Battery is fine all year long.
OnStar is activated - Battery dies and drains itself everytime it's left standing.
OnStar disconnected - battery is back to normal.

Re: On Star draining the battery
 

What sometimes happens is when your onstar is not activated it may wake the module up and search for a signal. When the onstar module wakes up it can draw between 250mA to 400mA which at that rate of 400mA would take approx 1 and a half days to drain a battery enough to cause a no start. Also there is typically around 35 to 50 mA draw from all other components which could take your total draw to 450mA. Now add in a remote start or other aftermarket devices and you may get up over 500mA or more. That can drain a battery overnight.

Re: On Star draining the battery
 

Yep, before I removed the fuse, 2 days without driving the H2 it was a sure thing the battery would be dead, right after I removed the fuse the problem was gone.

Re: On Star draining the battery
 

I had this problem after I didn't renew my OnStar service. If it sat for three days in the garage the battery would be dead. The dealer told me exactly what Hum Tech said that I should deactivate the OnStar with the fuse because it can draw current while it continually searches for a signal. I pulled the fuse on the OnStar and I've never had the drained battery problem since!

Re: On Star draining the battery
 

so why doesn't this happen on every unactivated onstar vehicle? I have the original analog only and I can go 3-4 weeks between starting.

Re: On Star draining the battery
 

Interesting. I have not had any problem with battery drain from OnStar on either the H2 or Corvette. However, my OnStar is still active with the exception of the phone part.

Re: On Star draining the battery
 

Why it happens on some and not others is a mystery to me, i tend to call all modules PFM modules. A bunch of inputs go in, a bunch of outputs go out. What happens in the middle is pure f**kin magic.

Re: On Star draining the battery
 

Which leads on to if your being a dumb ****, you'll let out the magic smoke. Then its junk for sure.

Re: On Star draining the battery
 

Haha, agreed. The magic smoke is very important, lose it and your screwed

Re: On Star draining the battery
 

I pulled the 15A fuse on Saturday to disable OnStar. The green light went out.