Dennis Burford

Hi all,

My 86 has a problem I need help sorting out - mostly a suggestion where to start looking. The past couple days the dash indicators all flash (all messages and the warning indicator) and then the battery indicator drops to 10, and the car still runs, but lights are much dimmer, as if I'm running off the battery, perhaps with a trickle charge from the alternator. Previously a couple good revs would pop the battery indicator back up and the system would be bright and apparently charging as normal, but that is no longer the case, this morning I drove in wondering if I'd make it to work or drain the battery until the car died. I made it to work (50 miles). Physically everything looks fine. Is the alternator dying or should I be checking for a possible short in the system, or could this be a bad cell in the battery? (Don't know why previously sharp high revs would fix this symptom for a period of time).

Thanks for your input!

Dennis

928SS

same exact issue on mine, but it's intermittent. all the threads I searched led to 2 things - bad ignition switch or banjo connector / pcb board plugs being loose.

1 mechanic thinks it's the pcb board. I'm still wondering...

Mike Frye

I haven't had these problems, but did you check and clean all of your grounds? I'd start there. Also, there's an exciter circuit that has something to do with the charging, it goes through the volt meter in the pod and includes a resistor that can work it's way loose. The resistor is on the back of the PCB in the pod.

It sounds like bad ground/loose connection, I'd just work my way through the electrical system cleaning everything IIWY.

928SS

BTDT on the grounds... good idea on the pod resistor/exicter circut.. was wondering about that. as my switch seems fine and banjo connectors are all very tight. plugs seemed ok, I think.

if I smack the pod, sometimes everything goes away till I hit the next magic bump that sets it off again, so the exciter gremlin could be there on mine anyway.

next week I'm gonna bring it into the shop and have'em pull the cluster, ck the PCB/exciter thingy. I'll let you know what they find...

thx for the idea!!

Mike Frye

Here's a pic of what mine looks like. I think yours should be the same:

Alan

Well - I'd suspect the alternator failing first based on your symptoms and the previous remedy... could also be the exciter circuit in the dash.

If your system voltage level drops below 12v (for real - use a DMM to check) then you are not charging at all and are running solely on the battery...

check the voltage level on Central Electric connector M13 or L23 (same thing). This is the exciter line to the alternator - it should be close to system voltage when running (12v+) If not you will need to get the alternator checked. Does your charging light come on with the ignition on but the car not started?

Alan

Dennis Burford

Thanks all, I'll check the voltage at the proper connector, although I suspect I'll see what the gauge reflects, the exciter circuit and the alternator, if I can make it home. I'll also try smacking the pod to see if it makes any difference. Hope she starts up charging (usually the case, then fails on the road after awhile - heat? bumps?) so I can get her the 50 miles back.

Mrmerlin

you might have a brush thats worn down in the regulator housing, this is easy to replace but requires alternator removal.

928SS

well, finally got my flashing disco dash fixed.

turned out to be the infamous exciter thing on the pcb board pictured above. apparently, someone had tried to solder it and it wasn't pretty. the contacts for the connecters were all trashed/oxidized so bad they were black in places...

only complication - that resistor thing on the early models is NLA. I found a used one at north hollywood spedometer - $5.00

so I put in a new pcb board w/the used resistor thingy and the process even cured my magic jumping temp gauge!! whoo hoo!! all works perfect now

hope this helps

dr bob

Rob, amd anybody else reading along: FWIW, that's a VERY COMMON generic wirewound resistor. Places like Fry's, Marvac. Delvac, and probably even Radio Shack sell them.

Once the car is running and the alternator starts charging, they are "self exciting". The voltage internal in the alternator upstream of all those primary diodes is high enough to provide the excitation current, so current no longer flows through that bulb-and-resistor circuit. No current flow means nothing to light the "charge" light bulb. If you are seeing fluctuations in system voltage --after-- the light goes out with engine running, look in the alternator itself. For the symptom where it won't start charging until the engine has been rev'd up, the PCB/resistor/lightbulb/connectors arae deserves a careful look.

928SS

thx dr bob, mmlerin and alan! electifying info as always...

well, it came back!! almost made it 40 miles.

another round at Hauser's found the voltage a bit low at 13.4 at 3000rpm. so we pulled the alt. & found a goofy brush that wasn't making full contact. replaced the regulator/brush thing and now it's at 13.8 or so at 3K rpms. also bench tested the alt to insure it was putting out a full 115amps (and a tad more).

then cleaned all the harness plugs up front and rechecked all the PCB connections/grounds.

friggin lights still come on!!! ignition key is cold, and when being wiggled a LOT nothing happens. kinda doubt the switch is the culprit... new battery, car starts very easily w/the new hi torque starter.

the CES computer and ALL other car electrics (even the HI intensity washer pump!) seem to be working perfectly - a miracle in itself I suppose.

guess we're going to pull the console next and ck all the connections there, as well as ck all the locks for a possible short/issue w/the fact alarm stuff although the fact alarm is disabled. if I find that my stereo guy did this I'm sending him on a hunting trip w/dick cheney..

"sparky" hauser (the 928 wiring guru) is teaching me to swear in german and hungarian. doc brown just shakes his head and is secretly happy I don't live closer to him.

the saga continues.......

928SS

1 interesting note re: courtesty lights - when doors are opened, the hatch light, door lights and center lights come on if in the proper posiiton. if the hatch is open only the center lights come on - not the interior door lights.

if the hood is opened, all interior lights come on...

does that seem normal to not have the door lights come on when the hatch is opened? maybe a short someplace or those silly lights are miswired again? they have been messed with a lot...

Alan

It is not normal and the hood should not trigger the interior lights at all... - do you have an aftermarket alarm or keyless entry system?

Alan

928SS

nope... just the fact alarm that is supposed to be disconnected/disabled... should be clean in that regard, although there were several aftermarket alarms over the years I suspect. should have all been pulled out though.

hmmm if the hood is activating interior lights, I wonder if there is a goofy alarm circut someplace that is shorting out or causing the dash lights to come on... are the dash lights supposed to flash for any alarm functions?

might be time to pull the glovebox and see what kind of rats nest is back there....

928SS

found it!!! only took 8 months of guessing and messing... and the answer was: grungy CES connection. apparently it got moved around a bit when the pcb was replaced which is why it seemed to settle down after that. then it just got progressively worse. one of doc brown's prodegy boys (Ole') stumbled on to it. only $75.00 to get it done! (not counting all the other stuff done 1st, lol)

guess we should add that to the list of easy stuff to check before tearing into anything complicated...

hope this helps

now off to the alarm. should be easy in comparision, I hope.