Dash lights go out, starter will not engage after engine shut off

[steve h]

The Combo relay is the second largest relay in the relay box -- a rectangular black relay that should be on the left side as you are facing the engine/windshield from the front of the car. (The largest/longest relay in the box, on the right side, is the lamp burnout indicator relay).

The MB part number (which if original is marked on the side of the relay) is 201 821 02 47. This is an extremely easy to find relay at wrecking yards, and was used in most W124 models Ive seen, as well as Gen 2 (1986-1991) W126 sedans and coupes, and many W201 models as well. I keep 4-5 extras of this relay -- over the years Ive had them go out in two of the four W124 cars Ive owned.

Hi Gerry,

Do you have any [combination] relays left as mine suddenly quit & is buzzing. The car wont run at all
Mine has the numbers : 2018210047 & 05898301

Thanks, Steve

 

[gsxr]

Do you have any relays left as mine suddenly quit & is buzzing. The car wont run at all
Mine has the numbers : 2018210047 & 05898301

Steve, do you mean the engine will not run? Or the wiper does not work?

 

[steve h]

Steve, do you mean the engine will not run? Or the wiper does not work?

We left the house & after 500 yds the ABS & ASR lights came on & simultaneously all the instruments shut down (I mean the whole dashboard).

There was also a loud buzzing noise under the hood which turned out to be the relay (2018210047)

We returned immediately to house ( engine running normally) but once the ignition was switched off, it would not crank to start it up again & the buzzing continued , except when the indicator were flashing ( right or left)

I removed the relay & the buzzing stopped, but it will not crank/run at all

 

[gsxr]

We left the house & after 500 yds the ABS & ASR lights came on & simultaneously all the instruments shut down (I mean the whole dashboard).
There was also a loud buzzing noise under the hood which turned out to be the relay (2018210047)
We returned immediately to house ( engine running normally) but once the ignition was switched off, it would not crank to start it up again & the buzzing continued , except when the indicator were flashing ( right or left)
I removed the relay & the buzzing stopped, but it will not crank/run at all

Ohhhhhh. That is WEIRD. The buzzing relay is likely a symptom, not the root cause. That relay is for wiper function and should not affect engine cranking or running. You may want to start a new thread about this issue... also check battery terminals, make sure both 10mm and 13mm nuts are tight on the positive terminal.

 

[steve h]

Ohhhhhh. That is WEIRD. The buzzing relay is likely a symptom, not the root cause. That relay is for wiper function and should not affect engine cranking or running. You may want to start a new thread about this issue... also check battery terminals, make sure both 10mm and 13mm nuts are tight on the positive terminal.

That's what I thought. I could not see why this relay would stop the car running.
When I connected the diagnostic box, it came up with no faults ( stored or current)

 

[gerryvz]

Check your battery; consider replacing it with a new one.

 

[steve h]

Check your battery; consider replacing it with a new on

I thought the same as you, that the battery was failing under load, but it checked out OK

 

[steve h]

Ohhhhhh. That is WEIRD. The buzzing relay is likely a symptom, not the root cause. That relay is for wiper function and should not affect engine cranking or running. You may want to start a new thread about this issue... also check battery terminals, make sure both 10mm and 13mm nuts are tight on the positive terminal.

Any ideas on what could cause total failure of dashboard instruments & when I turn the ignition key to the start position, there is nothing.With the key at position 1, I can hear the fuel pump building up pressure & the lower dash lights are working (ASR/ABS etc) but at position 2 it does not crank, totally dead. I haven't received the new (used) relay yet, should be here tomorrow.

 

[gsxr]

Steve, a few different things come to mind, but it will be time consuming to troubleshoot. Random thoughts:

1) Failed ignition switch (electrical item behind lock cylinder)
2) Factory alarm system causing starter lockout (this would not cause dash lights to go out when driving)
3) Check all fuses in fuse box AND on the BM/GM module in the CAN box
4) Very long shot - swap the BM/GM module (this is a power supply for other items, and OVP function also)

I'm assuming the lower engine harness is good or has been replaced? If not, that can cause issues related to the starter / alternator...

 

[steve h]

Steve, a few different things come to mind, but it will be time consuming to troubleshoot. Random thoughts:

1) Failed ignition switch (electrical item behind lock cylinder)
2) Factory alarm system causing starter lockout (this would not cause dash lights to go out when driving)
3) Check all fuses in fuse box AND on the BM/GM module in the CAN box
4) Very long shot - swap the BM/GM module (this is a power supply for other items, and OVP function also)

Im assuming the lower engine harness is good or has been replaced? If not, that can cause issues related to the starter / alternator...

I'll work through all these items , once the relay arrives. It all started when the relay went kaputt......

 

[steve h]

Steve, a few different things come to mind, but it will be time consuming to troubleshoot. Random thoughts:

1) Failed ignition switch (electrical item behind lock cylinder)
2) Factory alarm system causing starter lockout (this would not cause dash lights to go out when driving)
3) Check all fuses in fuse box AND on the BM/GM module in the CAN box
4) Very long shot - swap the BM/GM module (this is a power supply for other items, and OVP function also)

Im assuming the lower engine harness is good or has been replaced? If not, that can cause issues related to the starter / alternator...

Received the relay & fitted it......buzzing was exactly the same, in fact the replacement relay vibrated/buzzed like the original.
After careful inspection of fuses, I noticed that fuse #5 was defective. Very difficult to see, more like a hairline crack.
Changed the fuse, buzzing stopped & car started up normally, all instruments on dash functioned normally.
Amazing that this one fuse could cause so much havoc.

 

[nocfn]

If the voltage regulator has not been changed in 5 years, that may be an issue. If you can get batter charged to crank, check ro see if alternator is charging. I been thru similar stuff, batter lasting just 18 months and fine on a tender but driving shut it down in a quck few drives.

my case the original alternator was there and to replace the VR was slightly less effort than a rebuilt.