Brian B

I just got back from taking the shark out to play at night, which I hardly ever do. I noticed that the dash lights and headlights seem to dim a little at idle and then get noticably brighter when I stomp on the gas. I also noticed that my voltmeter warning light is really dim when I turn the key to start the car, but it seems bright when I shut the engine down.

I put a new alternator in this spring and replaced the diode in the dash. the OB always starts up, even if it sits for weeks.

Is this normal?

Also, my voltmeter always reads low, dropping down to 10 when I hit the brakes, but going up over 12 at speed. I checked the voltage at the battery and I am getting 13v or so at 2000 rpm and over 12 at idle (unless everything in the car is running..when I get 12v on the nose)

What if anything should I check?

TIA
Brian

WICruiser

It sounds like your dash lights and head lights agree that the voltage is low at idle, so I would start with the assumption that the alternator is not putting out correctly at idle. First thing to check would be the belt tension. Since spring it may have stretched a little.

jpitman2

Put a meter across the cigar lighter at idle and see what you get. My gauge reads high (>15V), but meter says 14V steady. You may have a bad earth around the gauge /dash area causing voltage drops, but if your lights go dim....something is amiss.
jp 83 Euro S AT 49k

SharkSkin

Not sure what you're saying about the alt. warning light. Is it illuminated -- even dimly -- at any time the car is running? If so that points to possibly a bad alternator.

Brian B

Dave, the light is dim when the other idiot lights come on when the key is turned prior to starting. When the car is running, the light is off. When I shut down, the light goes on for a second. that's when its bright.

My headlights remain bright all the time, but I do notice that they dim at idle and then brighten up when I hit the gas.

SharkSkin

Sounds OK... check batt. connections, grounds, jump terminal, etc. Maybe go to Sears and get battery & alternator load tested(free or nearly so). The low voltage may be a result of many things, check the easy stuff first. What is the voltage at rest(not running, no electrical devices on)?

the flyin' scotsman

Brain............as Dave mentions do a battery voltage with the car not running, lights off etc. Then start the car and do the same test.

You may have a low battery due to not running very often or for long enough. If your tests reveal the battery at 12v when at rest and then ~14v with the engine running that indicates the charging system is operating. Put the battery on a slow trickle charge or battery tender to bring it up. Lights will always brighten when the engine is above a certain rpm.............the difference between idle and higher rpm is dependant on intial battery cahrge state and conditon of the entire charging system.

Hope that helps!

Brian B

Thanks, Guys. I'll check the voltage on the battery tomorrow.

What has been keeping me puzzled is why the low voltage light on the guage is dim on starting but seems bright when I turn the car off...I thought it might be a bad bulb, but it was bright last night. Any ideas??