Driving home from work today in my 1995 Legacy (normally aspirated), the radio suddenly shut off and the speedo/tach went to zero. The gauge cluster lights were on, but dim. The engine kept running normally. A few seconds later, everything was back on. For the remaining mile or so until home, dash lights and gauges did the same thing several times, going from normally on to dim lights and zero-ed speedo/tach, and the radio working and then no power. The engine ran normally the entire time.

I parked the car, had dinner, and fired the car up about an hour later. For the 30 seconds I ran it, it seemed fine -- all lights, gauges and radio worked fine.

All I can think of is a flaky ignition switch that is maybe intermittently cutting off the accessories. However, I think the headlights may be dimming when the accessories die, which may mean that the engine is running off the battery and not the alternator. I just can't see how an alternator problem is causing the radio to cut off completely. I also was surprised to see the speedo and tach go to zero -- shouldn't do that if it was an alternator problem.

Any thoughts? All wild suggestions will be considered, as long as they're car related.

--Bob

Probably want to poke around in the dash and check for loose wiring. If the car ran ok it's probably not the actual RPM and vehicle speed sensors, but related to your cluster and/or radio. They may use a common ground wire.

Probably want to poke around in the dash and check for loose wiring. If the car ran ok it's probably not the actual RPM and vehicle speed sensors, but related to your cluster and/or radio. They may use a common ground wire.

Thanks for the suggestion... a bad ground defininitely sounds like a possibility.

--Bob

Another suggestion. Check your fuse boxes and make sure you don't have a loose accessory fuse. Vibration from the engine and road conditions could cause this intermittent issue.

so about 3 months ago i had the same problem in my 03 wrx, the speedo and tach dropped to zero and the stereo cut out, but my lights cut out too and the car started to run real "funny" so not being a electrical guy i took it in to a shop and they poked around under the dash and found some loose wires, they fixed that and the problem went away.

I cleaned up all the grounds I could find in the engine bay -- I didn't see any grounds under the dash and did look around some. In addition, I pulled every fuse and relay (in the engine bay fuse box and under the dash) and pushed them back in. At the same time, I pulled apart a lot of connectors and reset them. One final thing: I installed a heavy braided ground cable from the battery's negative post to a spot on the intake manifold.

Since then, the car has run fine for about 120 miles with no further problems. With an intermittent problem, you just never know if you've fixed it though.

Thanks for the thoughts and suggestions!

--Bob

Just to wrap this thread up, the intermittent problem described above happened a few more times so I replaced the alternator and the car has been running perfectly for four months now. I'm sure the alternator was the problem, but it was an odd set of symptoms.

--Bob

I had the same problems I thought it was a bad battery no. Thought it was bad alternator. I put volt meter on the battery while it was running 12.67 12.57 12.43 going down I turned the lights off 13.5 13.58 13.62 going up. I turned lights on hi beam 13.25 13.27 steady turn them on low beam 12.7 12.6 12.5 down down. Then I thought turn off driving lights 13.5 13.58 13.64 then it was steady, turned on the driving lights then it went down down down. So I think mine is a short in the driving light wiring harness.

I made some measurements to check the alternator and got ambiguous readings. However, it does sound like there's a problem in your lighting circuit.

You could pull the connectors off your headlights and re-do your testing. If voltage still drops with the headlights switched on but physically disconnected, then there's a wiring problem. If the voltage stays the same, then there is not a wiring problem. If the voltage drops with the lights connected, then it could be that your alternator simply can't deliver enough current.

If you decide to replace the alternator, it was a super easy job on my 1995 Legacy. It maybe took 20 minutes, and that was at night with a flashlight in freezing temperatures.

--Bob

Yes there is a problem with the driving lights or fog lights some people call them. Maybe I was not clear in my post. If I let the car run with the driving lights/fog lights on it will discharge until the battery is near 10.2 volts and the tack goes dead the brake warning light comes on the radio dies. With the driving lights/fog lights off no more problem.

Yes there is a problem with the driving lights or fog lights some people call them. Maybe I was not clear in my post. If I let the car run with the driving lights/fog lights on it will discharge until the battery is near 10.2 volts and the tack goes dead the brake warning light comes on the radio dies. With the driving lights/fog lights off no more problem.
Don't rule out the alternator being bad. If the car is driving on the street, there should be plenty of electrical power for lights and other accessories, unless you have a massive aftermarket stereo. My replacement alternator had a test chart that indicated it produced 86 Amps at an alternator RPM of 2,500. Since there is a pulley ratio of 2.37:1, that's an engine RPM of only 1,100 or so. In other words, if you're driving down the street, the alternator should be able to power your lights indefinitely and the voltage should never drop.

One of the symptoms of my bad alternator was the tach suddenly going to zero, even as the car drove normally.

I got my replacement alternator at a local autoparts store for $135. It is a remanufactured unit made by Remy. I actually wrote a review of it online, which you can read at:

http://www.viewpoints.com/Remy-Remanufactured-Alternators-review-ddd04

Good luck!

--Bob