W115 240D Fuses and Relays

[AcIdBuRn]

Ive been searching high and low but I'm finding a bunch of conflicting information...

Can anyone give me a definite answer on what the under hood fuses and relays control and what amperage the fuses should be?

I'm talking about the fuse box on the driver side fender.. the fuse box on the passenger side firewall and the relays mounted under the fuses on the firewall. I'm also curious if there are any other fuses/relays that I'm not aware of.

Thanks!
-Chris

1975 240D 4spd

[gmog220d]

Oh man, that may not be an easy question to answer, unless someone around here has a lot of experience around W114/W115 in all their variety. I can say that I've seen some variation in the fuses and relays under the hood between 220d/240d and 300d, and the gassers too. I'm not surprised that the information is muddled as it seems different models with different equipment packages will have differing setups.

To piece that together I'd hit the books, chassis in particular, and have a look at all the stuff specific to your car year/model. For example AC/ventilation will have it's own fuses outside the main block, and those will be outlined in that section in the book.

Last year sometime I bought the suite of service books for W114/W115 in .pdf form for very little $, and have found them to be useful for stuff like this.

If nothing else post some pics of what you're looking at. Your '75 240D is probably the same stuff as my '74.

[Frank Reiner]

AB:

Main Fuse Box (Left side)


Fuse No. ---- Amps ---- Load
1--------------- 8 --------Clock, trunk & glovebox, dome & reading, hazard, turn signals

2 --------------16 --------Wipers, horns, lighter

3 ---------------8 --------Brake lights, back-up lights, inst. lights, seat belt warning

4 ---------------8---------Turn signal flasher

5 Not used

6 ---------------8---------Heater blower

7 ---------------8 ---------Clearance-, tail-, parking lights right, license light, inst. light, side marker

8 ---------------8 ---------Clearance-, tail-, parking lights left

9 ---------------8 ---------High beam right, indicator light

10 --------------8 ---------High beam left

11 --------------8 ---------Low beam right

12 --------------16 --------Low beam left, fog lamps

Aux. Fuses (Right side)

As mentioned above, the aux fuses are for optional equipment, such as power windows, sun roof, air conditioning, rear window heat, and radio.
The assignment of these fuses varies from car to car with the equipment installed. Additional relays may be found above the right front footwell.

[TnBob]

Full fuse changeout with spares for under $10 delivered from ebay.
300D,E proper fuses

[AcIdBuRn]

Is there anyway to verify what the AUX fuses/relays control? I know my car has rear defrost, power windows, and had AC.. it also had a plug that went to both front seat bases.. possibly heated seats?

[Frank Reiner]

Originally Posted by AcIdBuRn

Is there anyway to verify what the AUX fuses/relays control? I know my car has rear defrost, power windows, and had AC.. it also had a plug that went to both front seat bases.. possibly heated seats?

1) Be polite.

2) Remove the aux fuses one by one, see what does not work.

[kraakevik]

The auxiliary fuses from that era likely protect the power windows, air-conditioning clutch and supplementary fan in front of the condenser.

The fuses and holders have a tendency to corrode frequently--I finally replaced all mine on several cars with in-line glass heavy-duty fuses.

The bakelite or plastic plugs under the seats are almost certainly part of the infamous ignition-interlock system which often prevented the engine from starting despite the fact that the seat belts had been duly fastened.



Tim Kraakevik
kraakevik@voyager.net

[AcIdBuRn]

Originally Posted by Frank Reiner

1) Be polite.

2) Remove the aux fuses one by one, see what does not work.

...be polite? Did I say something out of line?

As far as number 2 goes.. I'm not sure if the rear defrost, etc.. work. The AC is half gone as well.

[AcIdBuRn]

Originally Posted by kraakevik

The auxiliary fuses from that era likely protect the power windows, air-conditioning clutch and supplementary fan in front of the condenser.

The fuses and holders have a tendency to corrode frequently--I finally replaced all mine on several cars with in-line glass heavy-duty fuses.

The bakelite or plastic plugs under the seats are almost certainly part of the infamous ignition-interlock system which often prevented the engine from starting despite the fact that the seat belts had been duly fastened.



Tim Kraakevik
kraakevik@voyager.net

This might explain why the p/o put a bush button start on the car wired directly to the starter solenoid. I am most likely going to delete the factory fuse and relay blocks and rewire everything with a universal blade fuse block over the winter.

-Chris

[kraakevik]

Chris

The under-hood fuse blocks on the passenger side were the only ones to give me trouble on six 114's over the years. I've never had a problem with the main fuse box, which is protected by a gasket--it's weather-tight.




Tim Kraakevik
kraakevik@voyager.net

[AcIdBuRn]

I'll definitely take a closer look at that one.

Is there an ignition relay? Something is sticking causing the e-brake light to stay on with the key off.

Thanks guys
-Chris