114 Heated Rear Screen problem

[gatur]

Hello All, This relates to my 1972 type114; My rear screen heater elements are not working and now it's winter I could do with them.... So far, I've removed the dash switch and established that there does not seem to be any 'live' connection there ie, no power. Strangly there is no mention of the rear screen heater on any of the fuse ways and anyway, they are all good.
So, first question, where is the power coming from?
Second, Can someone identify the individual functions of the pins on the behind dash 4 way connector? They are marked; 31, A, 15/54, E. This last will be earth/ground I guess.
With this info I should be able to start the process of elimination.

Thanks in advance,

Garry T

 

[television]

Hello Garry, I think that you are our only member with a 114 and sadly my data base stops long after your car, even the big USA forums do not have a section for your car, I do not know if you can get the info from here, but your car is listed.

http://www.detali.ru/cat/oem_mb0.asp?TP=1

Malcolm

 

[gatur]

Malcolm, I didn't realise that the type 114 was so rare... To me it is simply a 1972 - 250s with that chasis no. I certainly never had any trouble finding parts. I'm sure that the rear screen control knob was pretty standard on all the mercs of that period, so if anyone with knowledge of the wiring could help I'd be most grateful.
Cheers, Garry T

 

[Mikesmerc]

That brings me back a bit, had a few 114s years ago, a round button down by the hazzards that illuminates when pulled and push to turn off. I also remeber that these used to turn off automatically to save power. Where the fuse is, I cant remember but must be a large amp one.
Sorry I cant help.
Mike

 

[television]

As mikesmerc says you have a timer, the switch will be in series with the timer and it is the timers that go wrong. with the switch two wires will be the switch, the other two will go to the warning lamp.

Malcolm

 

[TimN]

I think that you are lucky to have a heated rear screen on a 114. It comes from the days when a steering wheel was an optional extra. My old 114 (some of which is still in the garage) certainly didn't have one.

A common problem with old heated rear screens is that the copper strip comes adrift drom the heater element or that the heater element blows or has hot spots failing some of the wires (for want of a better word). Sounds like for you have a failed relay. It is probably screwed to the bulkhead. Alternatively you have a blown or corroded fuse. It will be the big 30 amp so tak a look rotate it in the holder and see if that helps. If it is not frozen then put on the head lights then switch on the heater element and see if the lights dip. Or alternatively just check to see if you have voltage where once there was non.

A have an original MB part/service manual which was used some years ago to rebuild the engine. It is at my parents which I will be at next week. It is specifically for a 200D by the electrics should be the same. If you want me to take a look PM me with details where the plug is and I will check it out.

 

[gatur]

Malcolm and Tim, Thanks for your tips. I've now discovered the fuses for the heated screen in a separate box in the engine compartment. Replacing that gave me back power to the switch. Now I could hear the Timer/Relay buzzing as I tried to switch on. Located it way up under the dash in the passenger footwell. The buzzing was it trying to close but not managing. I'm hoping that this means that it is broken and is the where the fault lies. Anyway, I've ordered a replacement from Jacksons (who had it on the shelf..) and hope that will be it. The only further possibility will be that the screen heater itself is somehow not connected properly. I'm hoping that this is not the case as the entire rear screen was replaced by Mercedes 3 years ago. Fingers crossed...
Cheers, Garry T

 

[Mikesmerc]

From what I can remember you should be able to see the connections to the rear window from inside the car about half way up at each side, or is that the W123 Im thinking of?.
Mike

 

[gatur]

Mike et al..
I think I'm nearly sorted now. Yes the connecting strips are visable at either side of the window and I've put the meter accross them and all is OK. Also back to the multi plug that connects the relay. Also interesting is that the wiring and components appear to be the same as the later 123 models. I've managed to identify all the wiring from a later 1980 type 123 or 250s workshop manual. Very useful! When the new relay arrives, it should all work.
Thanks again, Garry T