I don't drive a lot at night so this issue was just noticed lately but may have been there forever. When driving the Hudsoncharges correctly at 13+ volts. I was travelling home recently in the dark early morning and noticed that with the headlights/parkers on the charging dropped to 11V. Then a little experiment and turned headlights off and still charging at 11V. So I would surmuise it is in the parking/taillight circuit. Can a bad earth affect the charging and cause this? We changed over the taillights a couple of years ago and it could be related to the changes there. What else could be causing this to happen? Otherwise the charging is all good just the parkers/taillights.
Since you didn’t mention a no start issue, it could be because of where in the vehicles wiring the volt meter is wired into. Next time you see 11 volts see what charging system and battery a reading directly from them.
I’ll add, started up my OT daily some 30 years ago, the volt gauge stayed right at 12-ish volts. Replaced the alternator. Still stayed at -12-ish volt. Got my meter out, charging at 14.xx. Test first, don’t be like Mike.
Indeed, start by verifying voltages at the important places. The meter in the car may be way off, or the part of the electrical system it's hooked to may suffer from voltage drop due to bad connections etc. A good start is to check what you actually have at the battery (on the battery poles themselves, not parts clamped on the battery, you don't want the risk of voltage drop through poor connections to give you incorrect readings).
My 64 Chevy truck, which was my daily driver for 12 years, would show a big drop in the dash mounted voltmeter as you turned on accessories. If you had the lights on and the blower motor, the dash voltmeter would drop to about 11 volts. I should mention that I got the truck from a young man who had about a half mile of extranous wiring run in the vehicle. I pulled it all out and re-connected most of the original wiring loom. At any rate, the first thing I did when I noticed this was to check the voltage at the battery when the accessories were on. With the engine running it was close to 14 volts. I then checked the voltage feed to the fuse panel inside the cab and it was 11 volts. After a little digging I found that the feed wire for the fuse panel had been replaced with a 14 or 16 gauge wire. I went back with a 10 gauge wire and fixed the problem. My point is that you should do some testing before you start cleaning/replacing things.
Is your alternator grounded with a wire on the backside? What size is the wire ? What type of parkers and tail lights? Did you try disconnecting the tail lights and parkers and checking the voltage ?
Verify voltage at the battery with a meter and compare with gauge in car. Check the basics first. Load test battery, check connections at battery and check grounds. Check belt for tight ... that sort of thing.
Absolutely, always diagnose it first. If you just start cleaning connections or changing parts you may get the problem to go away, but did you really fix the problem or did you get it to work temporarily because you yanked on a wire with a bad connection accidently getting it to work properly? When you have used the meter to narrow it down to the problem being between point A and point B you stand a far better chance of finding the actual issue and fixing it.
Listen to jaracer and G-son, do diagnostics. This is pretty obviously a voltage drop issue and doing point-to-point measurements to determine just where the voltage is disappearing will be critical. And you need to do these under load to get accurate numbers, making sure you duplicate the conditions (what loads were on) when you saw this. We're handicapped by lack of knowledge of just what components you have and how the harness is configured. And I doubt it's a grounding issue. Except for motor loads, poor grounding will reduce loads (and voltage drop) as a general rule.
Sorry, but no. First you fully charge and load test the battery alone. All testing of the car must have a good, fully charged battery first. Then check for any draw on the battery from the car. Then check charging system output. By then, you may have found the issue. After all that, check voltage with various accessories turned on.
So got around doiung a test today. Set the meter on voltage and the car running and charging at 14V. Then turned on the lights and no change to charging so looks like the gauge or connections are at fault. Maybe an extra earth on that gauge. At the moment the loom to all the gauges incorporates power and earth with each gauge taking a feed from I guess a common source. Anyway the test today allays my fears that there was a drain somewhere when the parkering lights were on.
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