Battery Drain

[GERRY1967]

I have a 1998 C180 W202 Petrol. Last April I replaced the old battery. The new one only lasted to January, I got a replacement, but this went flat a few weeks ago. I put a bulb tester on the neutral and the light stayed on. I took each fuse out individually and tested each time, the light stayed on. I took all the fuses out at the same time and the light went out. I put them in one at a time tested and removed them. The fault seems to be with fuses 10 and 30. I put all the fuses back except these two and the light was on showing a fault. Where could the drain or short be coming from?

 

[wongl]

What does it say on the fuse box? There should be a diagram on a piece of paper located in/by the fusebox.

 

[GERRY1967]

What does it say on the fuse box? There should be a diagram on a piece of paper located in/by the fusebox.

On the list it says fuse 30 is automatic heater control. Fuse 10 is the radio. I put back 10 as it did not make any difference. I have disconnected the light switch in the boot. This has reduced the drain by quite a lot. But there is still a drain. Tried taking them out again, fuse 41 shows up in various combinations but when I take it out with all other fuses in place no difference to the drain. Fuse 41 is on the heated rear window and engine residual heater circuits

 

[wongl]

On the list it says fuse 30 is automatic heater control. Fuse 10 is the radio. I put back 10 as it did not make any difference. I have disconnected the light switch in the boot. This has reduced the drain by quite a lot. But there is still a drain. Tried taking them out again, fuse 41 shows up in various combinations but when I take it out with all other fuses in place no difference to the drain. Fuse 41 is on the heated rear window and engine residual heater circuits

I have seen a problem with the 'automatic heater control' on a friend's petrol W168. The fuse kept blowing and I couldn't figure out what this is until I mentioned this to an Indie who pointed out to a big heater box in the air intake - the engine ran fine without it so the blown fuse was left as it to this day!

 

[BlackC55]

You need to check it with an ammeter really. In series from the earth on the battery. Lock the car too and wait for it to go to sleep. Should be no more than 0.06A

 

[GERRY1967]

You need to check it with an ammeter really. In series from the earth on the battery. Lock the car too and wait for it to go to sleep. Should be no more than 0.06A

The battery is in the boot, stupid place, so how would I lock the car and test?

 

[GERRY1967]

I have seen a problem with the 'automatic heater control' on a friend's petrol W168. The fuse kept blowing and I couldn't figure out what this is until I mentioned this to an Indie who pointed out to a big heater box in the air intake - the engine ran fine without it so the blown fuse was left as it to this day!

What does this thing do? Should I disconnect it?

 

[BlackC55]

The battery is in the boot, stupid place, so how would I lock the car and test?

Do you have an ammeter?

Connect the ammeter in series and push the lock over on the boot so the interior light goes off. Lock the car and wait for it to go to sleep. Thats about 15 mins. Then read the meter and see what it says.

If you are unable to do that, then get someone that has the equipment to do so. 202's are quite basic electrically so they don't take long to diagnose. A common item are the rear window motors, they get damp and the connector corrodes causing the CAN bus to stay awake.

 

[GERRY1967]

Do you have an ammeter?

Connect the ammeter in series and push the lock over on the boot so the interior light goes off. Lock the car and wait for it to go to sleep. Thats about 15 mins. Then read the meter and see what it says.

If you are unable to do that, then get someone that has the equipment to do so. 202's are quite basic electrically so they don't take long to diagnose. A common item are the rear window motors, they get damp and the connector corrodes causing the CAN bus to stay awake.

hi, I borrowed an ammeter. I disconnected the battery and left the car locked for 15 minutes. The reading on the meter was 12.52. I took out and replaced each fuse individually but the reading didn't drop, in fact it seemed to go up a little. Does any of this make sense?

 

[ToeKnee]

Have a look on YouTube for "checking voltage drop"

 

[Ted]

Sounds like you have your meter set to volts, not amps.

 

[BlackC55]

hi, I borrowed an ammeter. I disconnected the battery and left the car locked for 15 minutes. The reading on the meter was 12.52. I took out and replaced each fuse individually but the reading didn't drop, in fact it seemed to go up a little. Does any of this make sense?

12.52A?
Did you connect it in series?

 

[GERRY1967]

12.52A?
Did you connect it in series?

Yes I did on the earth wire

 

[GERRY1967]

There is a new twist. Went to get petrol yesterday and flap on the filler wouldnt open. Tried unlocking and locking the car until it opened. Today the boot wont unlock. Tried time after time. And unfortunately the lock barrel doesnt work so I cant open the boot at all!

 

[BlackC55]

What about the button inside?

 

[GERRY1967]

That won’t open it either

 

[GERRY1967]

Ive been trying to free the boot lock with wd40 but no joy. Sometimes the petrol cap locks. I can hear the pump but the boot wont open even with the switch inside.