Parasitic battery draw?

[sisyphus]

Car wouldn't start yesterday morning, upon turning the key the dash went flat. I was able to jump it, when it threw the CEL and a code for the coolant temp sensor short to ground. Would that be enough to drain the battery overnight? I seem to recall having a bad one years ago but it didn't do this.
This is a 99.5 Jetta.

 

[wonneber]

With the key off the ECU should not send power to anything.

 

[sisyphus]

With the key off the ECU should not send power to anything.

HA! That's what I thought as well. Turns out it was the radio. Open circuit in the radio unit. It was trying to eject a cassette (I think), and drawing about 1.5A It was enough to kill the battery overnight.
Weird, because I was just replacing a CV joint the day before and I was kind of freaked out by this.
I was also amused that the radio fuse is 25A.

 

[Nero Morg]

Did you disconnect the battery when doing the axle? I've noticed sometimes my CAN adapter module for my aftermarket radio sometimes boots the radio up when you first hook the battery up, and won't shut off. Pulling then plugging the fuse back in always cures it.

 

[wonneber]

HA! That's what I thought as well. Turns out it was the radio. Open circuit in the radio unit. It was trying to eject a cassette (I think), and drawing about 1.5A It was enough to kill the battery overnight.
Weird, because I was just replacing a CV joint the day before and I was kind of freaked out by this.
I was also amused that the radio fuse is 25A.

I was referring to the coolant sensor.
The radio will turn on even with the key off so there is power to things.
The amp probably takes more power then the radio.
Do you have the Monsoon radio?

 

[KrashDH]

I was referring to the coolant sensor.
The radio will turn on even with the key off so there is power to things.
The amp probably takes more power then the radio.
Do you have the Monsoon radio?

The amp is known to have a parasitic draw. I had this in my car and couldn't track it down forever. When I did, I installed a relay that would kick the amp on with key on power. With key off, the relay connection was cut so there would be no way to get power to the amp. I just mounted it compartment that has the amp.

Haven't had an issue since.

 

[BigAndy]

There was a thread very recently with a member who had a parasitic draw that killed his battery overnight. If I can find it I'll post it. The person was very thorough in troubleshooting the problem and their process may help you with yours

 

[BigAndy]

Here you go - hope it is helpful.

https://forums.tdiclub.com/showthread.php?t=508236

 

[kcunniff]

HA! That's what I thought as well. Turns out it was the radio. Open circuit in the radio unit. It was trying to eject a cassette (I think), and drawing about 1.5A It was enough to kill the battery overnight.
Weird, because I was just replacing a CV joint the day before and I was kind of freaked out by this.
I was also amused that the radio fuse is 25A.

Love that you're still playing your cassettes!

 

[sisyphus]

Okay, here's an update. There's a further problem somewhere. Jumped in the car to take the kids to camp this morning and the battery fell flat when I turned the key. So I'm back to pulling fuses. Edited to add: The fan control module is a strange component. I had a bad one in the '01 that I resurrected from a field, and it gave me endless trouble. The symptoms covered just about everything.

 

[jokila]

This youtube is from CoolAirVW. Excellent way to find your problem child.

https://www.youtube.com/watch?v=gNTmrwiPe6g

 

[BigAndy]

Okay, here's an update. There's a further problem somewhere. Jumped in the car to take the kids to camp this morning and the battery fell flat when I turned the key. So I'm back to pulling fuses. Edited to add: The fan control module is a strange component. I had a bad one in the '01 that I resurrected from a field, and it gave me endless trouble. The symptoms covered just about everything.

Did you go through the post I put up for you earlier?

 

[BobnOH]

There is also this Technical Bulletin from VW-
http://pics.tdiclub.com/data/500/TSB_27_08_04_Matrix.pdf

 

[wonneber]

Okay, here's an update. There's a further problem somewhere. Jumped in the car to take the kids to camp this morning and the battery fell flat when I turned the key.

Did you charge the battery fully and have it load tested?
I'm wondering if it's going bad.
How old is it?