Please, I need help desperately! The alternator requires that the circuit between it, the battery, the starter, and the warning lights be complete or else the alternator will NOT charge the battery AND the alternator is taken out of the "charging loop" leaving the car to only run as long as the battery has charge.

I need to find out what the actual wiring is behind the dash or in other words, what the entire charging path is..... from the dash warning lights into the engine to the starter, the alternator, the battery, etc...

The battery is brand new and checked good.
The alternator is brand new and doubly checked also good.
The starter is brand spanking new and triply checked good, too.

Now, the warning lights are NOT coming on when I turn the ignition on except sporatically. When they come on, everything is fine and everything gets charged, but they only come on when we hit a bump or something.......

HELP! Need to know the charging path..... have checked all the obvious wires to all of the above components under the hood and fuses, etc.... need more info.

Yes, I'm a single female but I taught electronics in the NAVY and know a little bit about what I'm doing but I don't have any wiring diagrams or schematics to really go by..... Don't need the schematics.... Just need the actual hard-wiring path....... Where's the darn wires come and go from under the dash to the engine?


Thanks for anyone that can assist me.............

I dont know about this model (I have one myself but have not had to look at this circuit yet) but generally the circuit containing the warning bulb is part of the exciter circuit for the alternator, if the bulb blows you get no chargeing. in your case you are getting sporadic. chargeing, so maybe you have a bulb that is blown but making sporadic contact, when you go over the bump, the contact breaks and the chargeing stops. I cant swear to this but it might be worth swapping out or changeing the instrument bulb. I will have to check the wiring diagrams (I am a draughtsman by trade so can read these ok) to confirm this which I will do shortly and get back to you.
Grendel

would this be what you are looking for:-
Grendel

Attached File(s)
 940_chargeing.pdf ( 16.38k ) Number of downloads: 115

Hey Thanks! I think it might be..... it's definitely more detailed than I had before, so I will give it a shot in the morning...... The bulb itself in the row of warning lights (the alternator - battery warning) is NOT blown..... the lights just only come on once in a while...... when they do, that particular bulb, along with the others, illuminates just fine...

Thanks again.... I'll let you know.... I'm not quite sure which side of the instrument cluster this is on ... wish I had an exploded diagram that actually showed where the bulbs were and the number designations... etc.... we'll give it a shot though.l

thanks again....

The bulb itself in the row of warning lights (the alternator - battery warning lamp) is NOT blown..... the lights just only come on once in a while...... when they do, that particular bulb, along with the others, illuminates just fine...

Of course, they're all supposed to come on briefly when you first turn on the car, but I'm also aware of when they come on while driving after hitting a bump or whatever, because of the overdrive arrow on my car that remains permanently on because we had the O/D switch taken out of the circuit because it kept staying on constantly.... guess I really should reconnect it and replace the relay, which I feel certain is what was wrong with that.... anyway, another post gave me a great diagram to start with.... If anyone has any further exploded diagrams, feel free to post!

Thanks again.... I'll let you know.... I'm not quite sure which side of the instrument cluster this is on ... wish I had an exploded diagram that actually showed where the bulbs were and the number designations... etc.... we'll give it a shot though.l

thanks again.... both of you!

Oooops! Just noticed that the post was by the same person..... Thanks!

this might help
Grendel
and just spotted the apology - no problems I work quick sometimes :)


Attached File(s)
 instrument_wd.pdf ( 44.88k ) Number of downloads: 110

Ah, HA! Yes, this should be all I need to at least physically find it and do some continuity checks, etc..... thanks SO MUCH!

Nise

This forum is SUPER! Wish I'd come here first prior to dropping off my car into unreliable hands....!

Looking at the wiring diagram I would check the feed to the instrument lights at D4 from the ignition swich - it seems if you lost the power there all of the lights wuold go off, as would the exciter to the alternator, maybe the problem is at the ignition switch?
Me - assume a woman could not do anything she set her mind to - well anyone who says that hasnt met my wife. She once did a test to see which job would suit her best and her scores were so good they said she could do any job she set her mind to, I fully admit she is brighter than me.
As to the bulb - I was just thinking of those instances where the filament breaks but somehow (for a short time) retains contact intermittently. Now looking back I see you said you lost power to all of the instrument lights.be careful as that feed (C16) to the alternator also seems to connect into the ABS system too.
Grendel
Oh and :00000732: to the forums :)

Here is the ignition switch end of the WD. Ilooking at that I would have thought you would lose the whole ignition if it was the switch, so it might be wiring on that circuit- dont ask me where the wires run though - I am still trying to solve the mystery of no rear fog lights on my 91 turbo model. I guess at their age these cars are allowed a few quirks - I mean how many cars live long enough to need the wiring replacing??.
all the best luck in solving the puzzle - let me know how you get on.
Grendel

Attached File(s)
 ignition_sw_fuses.pdf ( 71.31k ) Number of downloads: 82

Most of the modern vehicles deploy printed circuitry in the dash.Some times these break and may not visually show up. You have to trace the circuit lines individually for continuity with the help of a continuity tester or an ohm meter. There is a common ground for all these warning lamos. If all of them fail to show up you better check the grounding circuit.

Hi I've just bought a 1991 940 SE turbo estate, and have got the same problem, but I discovered that if I remove and then refit one of the warning light bulbs with the ignition turned on all the warning lights work but if you fiddle with it they go on off, almost as if they have all got to have a good contact or none of them work, as for the charging light someone at somtime has rewired in a new light next to the ariel switch, they have done this by running a wire from the alternator to the new light and the other pole to earth, when I checked the alternator output with the light glowing there was no charge, but when I revved the engine enough to put the light out it showd a charge of just over 14 volts, so if all else fails you could try doing the same, as for the warning lights as soon as I get the instument panel out and sort out continuity etc I will get back to you

:banana:
Me again, have just found this website which seems to answer a lot of questions,
electrical instruments

I have a 91 940se and my instrument lights for oil, bat, ect dont light up all the time. In the morning when its cold they light up most of the time but after driving it and restarting they doint turn on and i have to rev the engine to 3K for the alt to charge if not the car will die and the battery drains. Once in a while when i get gas an i reset the tripomoter the lights turn on and it charges fine. Should i remove the guage panel and tighten up the nuts and what ever is loose and check the flex board for cracks?

These symptoms just showed up on my '93 940. I found that momentarily connecting the small red wire on the alternator to +12v will kick the charging system into action after the car is started. Touching a quarter between the terminal of the small wire and the main charging terminal seems to work well for this (don't let it touch the alternator case!).

Can these symptoms be caused by a fault in the alternator (such as worn brushes), or must the problem lie elsewhere (loose connection)?

Thanks,
Will