'88 W126 - dead gauges - buzzing relay under hood (bad cluster relay?)
 

Hi guys,

Moms '88 300SEL has been pretty trouble free for years, but now a couple of issues, not sure if the two are related. One is if the car sets for a couple of days (which is usually does) without being started and it is damp outside, the car is very slow to start. You have to crank quite a bit before it will start.

Today a new issue, not sure if the two are related. I was going to drive her to town in her car and when I started it I noticed all of the gauges were "dead". The tach, fuel gauge, temperature gauge, and oil pressure were not working. The dash lights were however. I also heard a buzzing sound under the hood I had never heard before. I popped the hood to see if any fuses were blown (and none are), then I heard that buzzing sound was coming from the fuse box, it was coming from a relay which I will picture below. I am not sure if the two issues are related, but odd the gauges had just died and that relay was buzzing. My dad had just drove the car about an hour before to get a part for his truck and he said the gauges were working fine. Questions are - could this relay be related to the gauges not working and/or the hard starting issues? The car started easy today however and was actually running when I checked the fuses and heard that relay. It is also buzzing when you turn on the ignition and the car not running. Thanks!!

*I did copy the number and did a little ebay search and appears this may be the instrument cluster relay?? I just wanted to be sure. I doubt that has anything to do with the hard starting problem.

Mercedes Benz Instrument Cluster Relay 201 821 00 47 See Item Description | eBay

It is the shorter black relay toward the back of the box making the noise...

http://i39.photobucket.com/albums/e1...ps7rhprcep.jpg

This relay with the white numbers you see is the one making the noise. If you touch it, the sound gets louder...

http://i39.photobucket.com/albums/e1...psvucuz5qb.jpg

http://i39.photobucket.com/albums/e1...psy0ziptw3.jpg

http://i39.photobucket.com/albums/e1...psmhpxfgpc.jpg

Next question is how to you remove it? We have tried for about 20 minutes pulling it straight up and it will not budge. :confused:

Update - I looked at fuses again and #6 looks flaky. I was told that could be problem. I am going to replace it tomorrow first and see what happens. Not sure why though it would cause the relay to buzz?

Thanks for all of the replies.

Thought I would update incase anyone else ever has the issue. It was a blown fuse. It appeared OK, but it wasn't. New fuse and all is well. :)

Always best to check the simple things first. Glad you got it figured out

Yes! Thanks!

'81 300SD with same behavior (minus the relay buzzing, or at least not that I heard): fuse 12. Per the inside fuse cover, it corresponded with the dash and brake lights which also didn't work. Just in case someone runs across this thread with an earlier model.

I came across this for the first time twenty years ago, owning my first Mercedes. Replacing all the fuses gets rid of irritating basic electrical gremlins and it's cheap to do.