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Discussion Starter #1
Dealership quoted $1400 fora new SRS module. I picked up a used one for $30 to install myself. I found the module behind the ashtray on my 1988 260E. Assuming I can get to it (?) from the side any advise from someone who has been there on switching it out. I'll disconnect power. I guess I'll still need the Dealer to clear the code and shut off my light? Hal
 

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1990 W124 300TE-24 3.4 AMG, 1991 W126 300SEL
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Correct me if I'm wrong, the sensor box behind the ashtray is for the seat belt tensioner...???
 

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300TE 4-Matic 300GD
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Hi hcalmar.

First to Rafmar, yes the SRS control unit controls the output to the belt tensioner.

The question to ask when a dealer wants to change a SRS control unit is, what made it go sour. If they just want to change the unit, and do nothing more, I would be very suspicious. Normal procedure would be to change the unit(s) and then seek to find what stumped the controller. Very often the reason will be worn rings in the steering wheel. A bad overall voltage situation in the car must be rectified before unit swapping and testing. Low voltage and bad ground conditions are a real controller killer.

The question to ask yourself is what do I know about this used unit. Has it been subjected to any jolts or impact? Is it the right type? Will it have a fault that would blow the airbag or belt tensioners right away? Do I know exactly which car this comes from?

All models before september 87 I think have a W126 type controller with a different voltage and connectors. If you try to connect one of those, the connectors won't fit. If you get a workaround that, you will fry it instantly. The ones produced after september 87 did not have a voltage regulator or a reserve power source. They have extra circuitry to evaluate if the belts are used and if someone is in the seat. Only if these two conditions are present will the bags inflate. On the former, the bags will inflate with or without a passenger. Think of this when you want children in the front.

So the best thing to do is to ask the dealer to try your used one if it's of the right type. If it is OK, they probably won't guaranty anything at all. I know I wouldn't.

Every time you switch the ignition on, the controller tests itself, shining the RS lamp for approximately 4 seconds. If it shines after that, there is something wrong. It doesn't give any fault codes, so there's nothing to clear.

I used to do those kind of jobs myself. Then one day a lady picked up her Benz, and 300 meters down the road, Wham! The bag blew in her face, and she got two black eyes. I was inches away from an official investigation.

So from that day on, no more SRS units for me. I use a friend who runs a certified MB shop with all necessary equipment. Getting hold of the right equipment to test SRS would cost a fortune.

1400 is a lot of dough. And how much labour? As a counterweight, consider how much it is for a bag(s)? Belt stalks? If you do your own controller, and the bags and seat belt stalks go, you will for sure need a new controller again. And maybe sunglasses and a raw beef or two.

Best of luck.

Regards

Geir
 

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Discussion Starter #4
The dealer tested everthing and says I need the controller! I get your point, and if I had not just spent 4K on more repairs than I care to mention over the last year keeping the car sound I might "do it right" but I have to find a cheaper way or unplug the SRS light on the dash and hope it works if I need it.I drove a car for years without an airbag!!!!
 
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