: voltage drops when car in drive



louie k
04-16-06, 02:00 PM
i have a 1995 cadillac eldorado with the northstar motor. When the car is in park i have about 12 volts, when i put the car in drive the volts drop rapidly down to about 8. When i put the car back in park the volts go right back up to 12. The belts are working. does anyone know what might cause this?

thnx in advance
louie

eldorado1
04-16-06, 03:11 PM
How are you measuring voltage? I wouldn't trust any gauges... Use a volt meter at the battery terminals and confirm those readings. 12 volts is very low, you should be seeing around 14 at idle.

1993 eldorado green1
04-16-06, 03:20 PM
yep, what eldorado said. 14 at idle and it should stay about the same in drive although it may drop a little if your running accessories and such.

dkozloski
04-16-06, 03:21 PM
If the lights are flaring from orange to bright with engine speed, the battery is shot.

Zorb750
04-16-06, 04:01 PM
Or your voltage regulator is bad.

Same thing if you hit the brake and the headlights momentarily dim a bit and come back (less than a second).

louie k
04-16-06, 08:11 PM
it says how many volts for the battery in the dash. when i start the car and let it idle it says 12.5 or around there, then when i put the car in drive it drops down to 8 and says battery volts low, i have air conditioning off, radio off, lights off in car. i checked the battery with a tester when the car was off and it said 2/3 full. i havent checked it when the car was in drive though.
When i hit the brake my headlights do dim of less than a sec and then come back

1993 eldorado green1
04-16-06, 08:17 PM
it says how many volts for the battery in the dash. when i start the car and let it idle it says 12.5 or around there, then when i put the car in drive it drops down to 8 and says battery volts low, i have air conditioning off, radio off, lights off in car. i checked the battery with a tester when the car was off and it said 2/3 full. i havent checked it when the car was in drive though.
When i hit the brake my headlights do dim of less than a sec and then come back


sound to me like its time for a new alternator man.. there not too bad to change

zonie77
04-17-06, 11:27 AM
There's a part in the alternator called a rectifier. If one of the diodes in the rectifier goes it acts like that.

blunted
04-17-06, 03:31 PM
Not to thread jack.. but you guys are getting me paranoid. Mines never at 14.. i get 13.5 max. I'm running at 7" Head Unit and 3 12"subs 1000W Amp, however I dont constantly have them blasting. Everything seem ok there? I got a Yellow Top as well.

eldorado1
04-17-06, 03:48 PM
Again, check at the battery with a meter to confirm. It could be a simple wiring problem, or nothing to worry about.

As an example, my ECM was showing 13.5 volts running, but I measured at the battery to be 14.5 volts. Now I know it's not the alternator, so I stopped worrying about it. A 1 volt drop is more than I'd like to see, but short of ripping out wires and buying all new connectors and smearing everything with new dielectric grease, there's nothing I can do.

Polski Polak
04-17-06, 07:59 PM
how do u know whether its the alternator or the battery, my headlights dim when I roll up my window should i look into a battery or alternator??? thanks in advance!!!

eldorado1
04-17-06, 08:34 PM
You can have your battery tested at Autozone or similar. The alternator can be tested in the car at the same.

acklac7
04-18-06, 12:31 AM
Or your voltage regulator is bad.

Same thing if you hit the brake and the headlights momentarily dim a bit and come back (less than a second).


Where is the voltage regulator located at ? ....For the past few years my headlights have dimmed when I apply the brakes....The engine will also make a slight noise at the same time....A buddy of mine said this was indicitave of the engine "looping" or something like that...BTW my volts rarely read over 13.5...when I have accessories running the voltage is in the mid-high 12's...Which is way to low I believe...I'd love to fix the problem...If it's something cheap and simple :)

caddyfanatic2
04-18-06, 01:27 AM
My headlights on my mazda 626 dimmed when i hit the brakes too. I figured it was something to do with the circuit that did the bulb check. But I've been noticing it on my Cadillac too. What could that be? Dont all cars do that?

thu
04-20-06, 11:57 AM
You can also just take your car down to Sears Automotive. They'll test the entire electrical system for you. Some stores to it for free; others charge a tiny fee. Many will waive the fee if you buy a batt, alternator, etc.

louie k
04-20-06, 06:59 PM
found out that it was a wiring problem,

thnx for all the help guys