w123 300td werierd alternator problem

[andydurrant]

The altornator doesnt charge the battery and shows no sign of fault on the indicatoer bulb when moving but when engine is off and key is out the charge warning light comes dimly and its brighter when you press the break pedal. I suspect either the altanator reg. or some king of weired earthing related problems. can anyone sujest any corse of action on how to solve / diagnose this problem. Its v strange and fed up of having to charge bat. in house over night and getting jump starts if i want to listen to wake up with wogan on my commute

Thanks

Andy

ps not that bothered about wogan in the morning just want it to work propely

 

[television]

The altornator doesnt charge the battery and shows no sign of fault on the indicatoer bulb when moving but when engine is off and key is out the charge warning light comes dimly and its brighter when you press the break pedal. I suspect either the altanator reg. or some king of weired earthing related problems. can anyone sujest any corse of action on how to solve / diagnose this problem. Its v strange and fed up of having to charge bat. in house over night and getting jump starts if i want to listen to wake up with wogan on my commute

Thanks

Andy

ps not that bothered about wogan in the morning just want it to work propely

I think the you have a diode S/C in the regulator pack, new pack cost around £15 two small bolts and it unplugs, from any Bosch agent.

malcolm

 

[sixpack]

Alternator

Hi Andy,

Suspicious about the light getting brighter when you press the brake pedal. It looks like there is an interaction between ignition controlled and non ignition controlled parts. I had similar problem, but on a Fiesta, it turned out the owner had replaced the stop/tail bulb with a single filament bulb (only one contact). This shorted the 2 contacts on the bulb holder and caused all sorts of strange faults when the brake was pressed. A wrongly wired radio could also cause problems if the constant live (for the memory), was connected to the ig. controlled main radio power wire. Have you done anything electrical lately ?

Hope this helps

Peter

 

[andydurrant]

no, no electrical changes recenty but got the part from lucas services and will put on later and let you know what happens

Thanks

 

[Hibbo]

Hi mate, how did you get on with the new regulator? How much was it?

From poking around my w123 300D I am aware of the following things;
The alternator warning light circuit is also part of the alternator exitation circuit. With the alternator disconnected the light does NOT light, even though there is current being drawn from the battery. There is no output from the alternator with this disconnected.

The light is dimmly growing as it is detecting a slight current draw from the battery, and gets brighter when you press the brake as the brake lights then draw current. It would probably also do the same if you switch the headlights on.

It shouldn't light at all through with the ignition off.

Have you got a Haynesy? There are full diagrams in the back of there.

 

[andydurrant]

well

got new regulator and made no differance started poaking round behind the instument cluster and light doesent come on at all any more, but what i have realised is that the insument lights (pad ware, main beams, carge etc) dont come on when you turn the ingnition on but not the engine but the instuments do go up. they all work as they should when the engine is on. I am at a loss with this weird fault any more guidance would be apreciated. will dig out my loop-ammeter tomorow and have more of a look got to dark tonight. See if where my charge current is goingif tis there and wats going on behing the dash.

thanks

Andy

 

[TimN]

Possibly corrosion on the tracks of the circuit board inside the instrument cluster.

 

[television]

The most basic test for charging is to turn the headlamps on and rev the engine,the lights should go brighter, there nothing behind the dash to stop the car from charging.

malcolm

 

[andydurrant]

ok will have a look today and let you guys know whats going on if i know

Thanks for you help

andy

 

[Hibbo]

As Malcolm has said, the headlight test is a good way to check, similarly you can put a voltmeter across the battery and check it rises when you rev the engine.

I think TimN is on the right track (pardon the pun), and I would have to disagree with malcolm. There IS something behind the the dash that can stop the battery charging - The wire from the alternator to the dash warning light must be connected or the alternator will not excite.
I know this is the case as I ran my engine with the plug disconnected from the alternator and a voltmeter connected directly to the output terminals of the alternator - reslut: no output (bar a tiny bit due to risidual magnetism). I do not know exactly how the system is wired or why this is the case, but it is!
If there is a dodgy track on the cluster causing an open circuit this would cause a lack of alternator output.

I opened my cluster to investigate a problem with my temp and fuel gauges and found a couple of lifted tracks. I simply soldered a couple of bypass wires on.

 

[television]

Hibbo is correct, a way to test is here.
http://www.autohausaz.com/html/auto_electrical_systems.html

The system is not on the MB dator base owing to the age of the car, any way the above thread will help you sort it out, the quick test is to turn the key to 2 and measure the voltage at the thin wire. should be 12volts (engine off)

Malcolm

 

[andydurrant]

Well got the loop-ammeter out today and took the dash apart and alot of the trax on the board are screwed, there was a small charge current but not enough to handel headlights (getting bout 5A) ect so it could ge the case that the circuitry in the dash is causing the probelem. Could this also cause the altermator to take current when engine was off? Could it be that the alternator has caused the other damage when it malfunctioned The alternator was taking 5A ish and the lead to dash was taking 1A ish. does this make sense to anyone?

Thanks

Andy

 

[television]

Well got the loop-ammeter out today and took the dash apart and alot of the trax on the board are screwed, there was a small charge current but not enough to handel headlights (getting bout 5A) ect so it could ge the case that the circuitry in the dash is causing the probelem. Could this also cause the altermator to take current when engine was off? Could it be that the alternator has caused the other damage when it malfunctioned The alternator was taking 5A ish and the lead to dash was taking 1A ish. does this make sense to anyone?

Thanks

Andy

Hi Andy, the wire that comes from the dash will be the exciter for the alternator, yes a fault on this circuit could cause damage. what I said earlier,there is a thin cable on the alternator, that is the exciter wire, with the ign: turned on there must be 12volts at this point, if there is not 12 volt the alternator cant work.

malcolm

 

[andydurrant]

Thanks for the reply,
have spent 1h repairing all the screwed trax on the board and will put the dash back in, in the morning and hope all is well for the commute and hope for the best. couldnt beleve how bad it was in there, there was some bad repairs already and put bout 5 or 6 new repir wires in there. dont know how it got that bad.

thanks

ps you are ment to put a commer in between to words the same in a sentance, eg in, in. sorry for my poor SPG.