befuddled by electrical problem
 

I've got an interesting voltage/charging system/electrical problem.

The warning lights all light up (Like a bad alternator) intermittently.

It seems to be independent of rpm high/low brakes on/off headlights on/off or stereo on/off (or any combination of those)

The dash gauge voltage is between 13 and 14+.

For instance, I just spent 45 minutes on the freeway, in stop/go thru 80 mph driving. The headlights and stereo were on. Randomly the dash warning lights flicker on/off fast slow - off for five minutes. on for 10 seconds. flickering. THey also flicker at different intensities.

I replaced the alternator a few months ago, it has maybe 2000 miles on it. I replaced the alternator belt last weekend, it was pretty worn, and I thought maybe that was the problem.

There doesn't seem to be any pattern at all to it.

What do you guys think the problem might be?

Thanks for your help.

Bad cold solder joints? Sounds more like a loose connection than anything.. maybe the computer is resetting because it is not grounded or loosing power. Maybe try to run a volt meter in line with the power going to your instrument pannel. Then you can see if the power to the panel is being cut, or if the panel iteself is having a problem (if the power is getting to the pannel constantly, but still flickers, its the idiot light cluster, if the power flickers, its the source (alt, battery, etc)).

When all the idiot light flashing happens, is the volt meter still at 13.5 approx???

if voltage is staying high during the flicker of the idiot lights, then the problem is probably cold solder joints in the CPU or a bad relay in the CPU or a loose power connection/plug to the ECU

Thanks for the replies.

The voltage is constant during the flickering. It only changes based on which accessories are on (lights/stereo/brake etc).

The voltage is above 13 most of the time. Since I put the new belt on, its been pretty steady about 14.

I wonder if I just didn't tighten the belt enough and its slipping? Sometimes I can make the idiot lights flicker by gooseing it, they will flicker as the rpms decrease to idle, then go off. Not every time, but maybe 60%.

I hope it isn't bad solder joibts in the cpu, that's a repair I loathe. I'll go run a search and see what the SOP is for that.

I will go check about for loose or broken connections. All the wires in the engine bay are so brittle it definitely could be that.

I"m off to buy some 8 gauge for the grounding circus. Perhaps I'll inadvertantly fix it by doing the grounds.

Any other ideas?

I don't know about series five cars....but on a series four, there is a relay in the CPU. When that relay is pulled in, the idiot lights light up. When the engine starts and the alternator puts out, that relay is de-energized and the idiot lights go out.

So. No output on a series four equals idiotlights galore.

Let me start again. That relay in the CPU. It has 12volts on its coil all the time. When the alternator is not running a ground is put on the relay to pull it in. That makes a circuit to turn the idjut lights ON. Wnen the alternator starts putting out....the ground on the relay goes bye, bye and the relay relaxes breaking the path to turn on the idjut lights.

Do the idiot lights come on when the key is to ON and the engine not running?? Should. And they go out as soon as the engine starts a running. Should.

ICEMARK repairs bad CPU'S the last time I looked. Almost for free. Almost. I don't see it being a grounding problem, myself.

OH. Do not over tighten the belt. Not good.

Yes, the idiot lights function normally during start up/key on.

Though they did flicker a few days ago immediately after start up. Normally they don't start to flicker for a minute or two after startup.

Thanks again.

I will check the deflection on the belt, thanks for the overtightening warning.

Tonight I pulled the CPU and tried to fix it. Since the last post the lights flickered more and more, finally they stopped. Then they didn't light during KEY ON, so I knew the CPU was the culprit.

After an hour with a 15 watt soldering iron, the lights come on at key on about 70% of the time, but only light to 1/3 brightness.

Does this mean that I didn't fix the CPU? I would guess so. Which part of the CPU should I concentrate on resoldering? There seemed to be hundreds of connections back there. I tried to really do the top 1/3 well, as those pieces were nearest the jiggly connector.

That sucks. Im having the same problem but its much more rare. Lights come on and off maybe for 5 mins at a time every two weeks?

Any opinions on which portion of the cpu the idiot/warning light panel charging circuit is located at?