W124 Gremlins

[brucemillar]

Folks

On my 124 Estate I have lost the Hazard Lights, Interior Dome Light (not working in any position) Radio and Window Switch illumination and operation.

All fuses test fine (I replaced them anyway). I have checked the two 10amp fuses on the OVP and they are OK.

What can have blown to cause this to happen please?

I do suspect that this may have been caused by my radio having the switched live and permanent live crossed? That had caused a substantial battery drain.

 

[boomtings]

Hi Bruce,

Heres a link to the ETM.
http://w124-zone.com/downloads/MB%20CD/W124/w124CD1/Program/ETM/ETM.pdf


page 15 (page printed as 110), shows the hazard switch , radio and dome light as connected to fuse 9.

looks like your dash clock ,warning buzzer and diagnostic socket 12v are all on the same fuse. if your also having problems with these then it must be an open circuit close to the fusebox.

 

[brucemillar]

Hi Bruce,

Heres a link to the ETM.
http://w124-zone.com/downloads/MB CD/W124/w124CD1/Program/ETM/ETM.pdf


page 15 (page printed as 110), shows the hazard switch , radio and dome light as connected to fuse 9.

looks like your dash clock ,warning buzzer and diagnostic socket 12v are all on the same fuse. if your also having problems with these then it must be an open circuit close to the fusebox.

Many thanks. Fuse 9 it was. Or to be more precise the clamps for Fuse 9. They looked spotless and I had continuity but at the actual pint of contact with the fuse there must have been corrosion. Removed the entire box and cleaned the whole thing up again, before applying some contact grease.

All is good again.

 

[brucemillar]

Well all was not good again. I fitted male & female red 'bullet crimps' to the switched and permanent live, in case anybody every wants to change the head unit in the future. Disaster: They worked fine the first night. Left the car overnight and returned to find that the radio had lost it's memory and would only power up when it felt like doing so.

The crimps were the issue (as I found when testing with a DVM and probes). I gave up and just soldered the wires. Now all is good again.

It seems that these things are a test of endurance and temper. I am not a fan of crimping anyway, it can be difficult to get the crimps to stay on. But I had not experienced them blocking current before.

You start to doubt everything you do with faults like this.

 

[optimusprime]

Good one bruce . I get to a point i dont want to take anything apart, for fear of it breaking .

 

[Smart320]

From reading all your threads I think you must have endless patience with anything mechanical or electrical Bruce!

 

[brucemillar]

From reading all your threads I think you must have endless patience with anything mechanical or electrical Bruce!

I should have. I am an engineer by trade ;^)

This particular car has tested all of my patience. However, that is the price of owning these beautiful machines on a budget. You are constantly fixing somebody else's fixes without really understanding what they were thinking when they "fixed it".

I still think that the prize for the greatest fix I have known on here, has to go to the wonderful Simon CARAT 3.6 who managed to fix my 3.5 V6 Pajero. A fix that gained world wide acclaim on the Pajero forums and has now been copied several times. https://www.mbclub.co.uk/forums/engine/195011-crank-position-sensor.html

That was extreme patience and fabulous skill and knowledge that you cannot really buy.

 

[optimusprime]

My father said if you have anything thats broken give it to my son [me] .He will take anything to bits to just see what its made of, and put it back together as good as new. And i am still like it now . I just need to get the wife to let me repair the washer .The poor thing is grinding on every wash .The bearing is shot in nthe drum .I know i can put it right .She wontlet me, and i know why , its just because she wants a new one . .I dint mind taking the Merc to bits .Its the parts that are so old , and the plastic parts just snap.

 

[brucemillar]

Well it carries on (and on)

I have a severe battery drain. Severe enough to drain the battery in 24 hours with a maintenance charger connected!!

The problem does appear to be the with the radio (Becker). If I remove the radio fuses the drain stops.

To the best of knowledge the wiring is good. I have removed the fader completely and terminated & insulated the wires for that. The speakers (front only) are connected directly to the euro connector then the head unit. I have checked that wires are correctly connected (they are marked 'front right positive' etc).

There is:
Black - Earth
Orange - Illumination
Red - Permanent live
Yellow - Switched live
Blue - Antenna

The head unit has an alarm LED that can be set to flashing or constant. I have it set to flash (and it does when the radio is off)

The radio switches off with the ignition in off position, or on its own on/off button.
The antenna comes up when the radio comes on, and goes down when it is off.

I tried crossing the two lives over but the radio simply did not power up correctly when I did that.
Any ideas what the problem is?

 

[optimusprime]

Bruce do you have the trusty free manual thats floating around .Lots in it for the becker radio insall ..So you have pin pointed it down to the radio ? .I woild say the old regulator .But this can be left to one side .

 

[brucemillar]

Bruce do you have the trusty free manual thats floating around .Lots in it for the becker radio insall ..So you have pin pointed it down to the radio ? .I woild say the old regulator .But this can be left to one side .

To prove my theory that it is the radio causing the drain. I may install my old Kenwood head unit. If that gives no drain then can I assume that the actual head unit is the culprit?

 

[grober]

I would guess the drain must come from the radio permanent live feed. Logically there should be no other way voltage should be getting to the radio. Time for the time honoured meter in series investigation. Easiest is possibly to substitute for the fuse in question on a suitable meter current range. [ should not be too high or it would have blown the fuse?] A drain should be obvious. Next disconnect the permanent 12v feed at the radio end- the current drain should disappear if the radio is the cause. If it doesn't its a wiring problem or other components fed by that fuse.

ps as optimusprime says a frequent cause of current drain is a faulty alternator diode. Alternator being permanently connected to battery live. [no fuses]

 

[martyz]

My father said if you have anything thats broken give it to my son [me] .He will take anything to bits to just see what its made of, and put it back together as good as new. And i am still like it now . I just need to get the wife to let me repair the washer .The poor thing is grinding on every wash .The bearing is shot in nthe drum .I know i can put it right .She wontlet me, and i know why , its just because she wants a new one . .I dint mind taking the Merc to bits .Its the parts that are so old , and the plastic parts just snap.

Perhaps she knows that drum bearings on washing machines are sealed units

(moulded into the drum) like I confidently took one to bits to find myself up a

gumtree....as for my Mercs,I just tickle them and all is well.

 

[brucemillar]

I would guess the drain must come from the radio permanent live feed. Logically there should be no other way voltage should be getting to the radio. Time for the time honoured meter in series investigation. Easiest is possibly to substitute for the fuse in question on a suitable meter current range. [ should not be too high or it would have blown the fuse?] A drain should be obvious. Next disconnect the permanent 12v feed at the radio end- the current drain should disappear if the radio is the cause. If it doesn't its a wiring problem or other components fed by that fuse.

ps as optimusprime says a frequent cause of current drain is a faulty alternator diode. Alternator being permanently connected to battery live. [no fuses]

Graeme

Many thanks. I took it apart again this afternoon. The power connector to the head unit was making a poor connection with the head unit. This was despite cleaning etc. I replaced that side with a nice new connector and soldered wiring. I also re-checked all voltages with a DVM.

The Permanent Live (yellow) is permanently live.
Switched Live (red) is switching with ignition.
Illumination (orange) switches with the cars lights.
Antenna (blue) switches with the ignition.
Earth (black) is a clean earth (zero volts)

I noticed (for the first time) with the car in the garage, where it is quiet!!

* Ignition & head unit off. There is a very faint whistle/whine from the speakers, that changes in pitch to match the flashing of the radio's anti theft LED?

* If I switch the LED from 'blinking' to 'off' then the whistle is is still there, with no change in pitch.

* This suggests to me that the head unit is outputting something to the speakers, when it is turned off.

With the head unit turned off, I checked all voltages again. All are zero apart from the permanent live which matches the battery voltage.

I am now starting to suspect the head unit is duff. I have left it connected tonight and will check the voltages in the morning, but expect it to have drained the battery again.

Any thoughts?

 

[grober]

The faint whistle or whine may be due to something oscillating in the radio perhaps indicating its not completely powered down. If it goes off when you disconnect the radio- chances are its in the radio. Only other possibility is its an interference signal being picked up by the wiring by something else in the car generating an RF signal and getting "rebroadcast" into the speakers. Again the most likely candidates would any semiconductor containing devices? e.g. Alternator

 

[optimusprime]

Perhaps she knows that drum bearings on washing machines are sealed units

(moulded into the drum) like I confidently took one to bits to find myself up a

gumtree....as for my Mercs,I just tickle them and all is well.

marty no the bearings can be done .I did it 4 years ago .But top and bottom is war depot [wife ] just wants to spend my cash on another washer instead of - my w124 . .

 

[d w124]

I am now starting to suspect the head unit is duff. I have left it connected tonight and will check the voltages in the morning, but expect it to have drained the battery again.

Any thoughts?

That stereo was on my Saloon Bruce
I only use the car once a month,twice if I'm lucky and never had a draining issue

 

[brucemillar]

Dash

That is good to know. Thank you. FYI: I had it in the car but not connected for a while. I only got around to connecting it up a few days ago, which is when my drain started.

I'm still at the investigation stage. Next step is to fit the old head unit and see if that causes he same issue?

 

[Ted]

Definitely the most straightforward next step, Bruce.

 

[brucemillar]

Okay

Battery completely flat again.

I have now plugged the old head unit back in using the same car wiring harness. Checked it is all working okay etc. I will now wait and see if this flattens the battery. One point to note There is no audible whistle/whine when the Kenwood is turned off!!