Z3M Roadster rear fog light relay

farside

Newbie
Joined
Feb 24, 2021
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3
Location
N Ireland
Model of Z
M Roadster
Hi all
Recently bought a 1998 Z3M roadster and trying to rectify a problem with the rear fog lights. As it is an 'M' front fogs aren't fitted. The original switch had been replaced by a rocker switch (latching type), and the rear fogs work ok. I found the original switch which had been left in the glove box and discovered one of the brass contacts had come adrift internally, which I fixed. However, it is a non-latching (momentary) switch, and when fitted the fogs only work if the button is held in.

So I guess the original relay just needs a momentary signal to make it latch on, and another to switch if off. RealOEM parts look up shows a 'control unit' at 3 times the price of a standard relay (part no 61356903410 ), so that indicates it is more than a simple relay.

My theory is the original relay is faulty and now only works when latched on by the rocker switch, or it has been swopped out for a standard relay.

Trouble is - I can't find it. I have looked at the various wiring diagrams but none quite exactly match the wire colours on my car. I think the rear fog light relay is K49 (and the front fog lights are relay K47 which is normally in the engine bay fuse box). One of the wiring diagrams shows K49 is located on a relay carrier under the dash, but the wiring colours and relay part numbers don't match my car.

Any help greatly appreciated....

Thanks
Kieran
 

Nodzed

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The fog switch on my M is a push button switch that stays in when the button is depressed and pops out when pressed again to turn off. Id say your switch is knackered.
 

farside

Newbie
Joined
Feb 24, 2021
Messages
3
Location
N Ireland
Model of Z
M Roadster
Thanks for the info guys.

Nodzed - I did wonder if the switch that I found was faulty and should latch, so bought another one on ebay. It was the same - non-latching. So, maybe 2 faulty switches. Then I dismantled both completely to check. It is a very simple switch, with no mechanism to be able to latch that I can see. But the fact that your car has a latching switch is interesting, and would solve my problem. I don't suppose you happen to know the part number?

Looking up Real OEM, the switch options listed are:

06Switch fog lamp and fog tail lamp109/199961311387054$48.12
06Switch fog lamp and fog tail lamp109/199961316901957$48.12
06Fog lamp switch109/199961311387055$32.07
06Fog lamp switch109/199961316901958$32.07

The 2 switches that I have are the parts listed as "Fog lamp switch". I don't know what the difference is to "Switch fog lamp and fog tail lamp" - maybe it's the dual switch for front and rear fogs?
 

Nodzed

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Thanks for the info guys.

Nodzed - I did wonder if the switch that I found was faulty and should latch, so bought another one on ebay. It was the same - non-latching. So, maybe 2 faulty switches. Then I dismantled both completely to check. It is a very simple switch, with no mechanism to be able to latch that I can see. But the fact that your car has a latching switch is interesting, and would solve my problem. I don't suppose you happen to know the part number?

Looking up Real OEM, the switch options listed are:

06Switch fog lamp and fog tail lamp109/199961311387054$48.12
06Switch fog lamp and fog tail lamp109/199961316901957$48.12
06Fog lamp switch109/199961311387055$32.07
06Fog lamp switch109/199961316901958$32.07

The 2 switches that I have are the parts listed as "Fog lamp switch". I don't know what the difference is to "Switch fog lamp and fog tail lamp" - maybe it's the dual switch for front and rear fogs?
Agree the top two are probably for non M's with dual fog lights, so 055 & 958 are probably the single switch for just rears, absolutely no idea what the difference between the two singles are though 🤷‍♂️
 

Nodzed

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Have a gander and this, could be both switches are just gummed up?
 

farside

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Feb 24, 2021
Messages
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Location
N Ireland
Model of Z
M Roadster
It’s a good thought, but no, switch has been completely dismantled and reassembled, all working smoothly.
The switch is simple enough, as you can see from the picture, there’s not much to it.
I think I’ll try to find a latching button version like yours as that would seem to be a simple fix.

8F52EC71-76AC-43A5-A6BD-89C8600F4719.jpeg
 

Nodzed

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It’s a good thought, but no, switch has been completely dismantled and reassembled, all working smoothly.
The switch is simple enough, as you can see from the picture, there’s not much to it.
I think I’ll try to find a latching button version like yours as that would seem to be a simple fix.

View attachment 177621
Well I would say looking at the terminals that is clearly a latching switch, designed to remain in contact to bridge the terminals. The bridge part is, I would say, broken/failed internally. I can find no other switch type option. 🤷‍♂️
 
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