W124 rear windscreen - Resistance value of heating wires?

[mercepor]

Hi,
I have a 300ce, from 1988. We recently changed the rear windscreen (new from Pilkington). The pilkington windscreen has an 0,4ohm resistance when defrost and blows the fuse within 5minutes. The electrician guy says that the defrost grid should have at least 0,6ohm in order to not to blow the 25A fuse.
We are in discussion with Pilkington and I would need an "official" source (maybe wis?) saying that the w124 300ce rear windscreen has 0,6ohm defrost grid.
Do you have an idea where to get that?
thx in advance

 

[gsxr]

Voltage / Resistance = Current
12.0v / 0.4 ohms = 30A
12.0v / 0.6 ohms - 20A

I don't know if the resistance specification exists in the FSM / WIS. Might help to get values from other 124's, but an accurate ohm meter is requried when you are dealing with values below 1.0 ohms.

 

[nocfn]

me hopes to be installing a new one soon....... Backglass that is...

 

[mercepor]

thx, I agree. In fact, the voltage is rather 14V and the respective A are 35A and 25A.
The discussion with Pilkington is a kind of reimbursement... since the windscreen cost 500eur.... but an official document is needed from Mercedes.
Pilkington has a stock of rear windscreen, they said that they measured all of them, all had 0.4ohms....

 

[gsxr]

thx, I agree. In fact, the voltage is rather 14V and the respective A are 35A and 25A.

Voltage at the battery/alternator is 14V with engine running... but due to voltage drop through the harness, you'll rarely see 14.0v at the consumer (in this case, the rear glass).

14.0v / 0.4 ohms = 35A
14.0v / 0.6 ohms - 23A

The bigger question here is, what is typical resistance, and we need more data to determine that.

 

[ngenius1]

It would be interesting to see what the resistance is at the fuse end, to determine how much the cable has added.
Oxidised cables can cause a lot of issues with current draw.