Erroneous Volt Meter Reading

[EchoLodge]

I have tried to run a thicker ground wire to my guages to solve bad readings. Guage reads fine until I start turning on the heater, stereo, blower, or lights. I have replaced the stock 51 amp alternator with a 95 amp and know it can keep up with the demand as I have checked it with a volt meter. Any suggestions other then to replace the VDO guage?

[tryan]

i always considered the voltage gauge to be of entertainment value only. i had one that would be off 1.5 voltes from the reading at the battery. i knew how much it was off and lived with it.


you are adding a load to a system that is designed, wired and fused at 40 or 50 amps. you might have to beef up the wiring to run all of your equipment at once. i would recommend doing so. turn everything on a feel the wires to see if they are getting HOT.

see if you can get an older amp probe amp meter that reads dc amperage and see what your pulling. i would bypass the engine harness plug and run a bigger fused wire from the alt to the main breaker terminal at the block and skip the engine plug. this is probably where your voltage drop is occuring. ( this is all, IFyou have a single wire alt that won't kill the battery) it would suck if your blower fan or something fried and took your harness with it.

[EchoLodge]

My Set Up

I run two bats that are connected via a continues duty solenoid. The bats are independent when the boat is off and the stereo runs off its own bat. When the boat is running the single wire alternator is ran with a 10 guage wire to the stereo side of the bats. The heater runs off the engine bat via the acc breaker. It drawls 8.5 amps. My stereo system drawls appro 65 amps. I guess I could run the heater off the o guage fuse block running the amps.

[EchoLodge]

I will just have to live with the false reading I guess. It is a 14 year old boat! A more accurate guage could be found on a new boat and payment.

[tryan]

i would panic in the 914 running 11 volts with the lights on at idle. i never drove the car at night until i checked the post voltage reading and got 12.8 with everything on. see how much the dash gauge is off.

rewire the dash gauge to your switching solenoid temporarly. disconnect the srock lead and run a jumper to your motor battery and see if you get the same reading. i would leave the heater fan on the motor side. you could pick up some noise in your sound system.

my friends grady white has a deep cycle battery and it can only handle the halogen spot light for about 15 minutes before his low voltage sensor is triggered, but it's an outboard.

you are working the batteries hard with that much draw. i would keep a good eye on the specific gravity and electrolylte level on the stereo battery. normal batteries gas off at 14.7 and gels don't like over 14.1 volts.
http://www.sonnenschein.org

[M3Fan]

Mine does the same thing. Apparently if you connect another ground wire to the opposite side of the daisy chain of gauges it will solve the problem. I will try it as soon as the boat comes out of storage.

[EchoLodge]

volt meter

I ran a sep ground to the volt meter already. I will keep the fan motor on the engine bat to reduce chance of buzz in the stereo. Ref the daisy chain, where does the chain start and end with the guages?

[gn6027]

EchoLodge, I assume you have seen the post at Inboardtalk.com about 1987 Gauges Going Crazy since it sounds like you added an extra ground wire as I recommended to Paul. I scanned in my 1987 schematic and attached it there.

It sounds like to me that you have added quite a bit of electrical load to the system. I realize you installed a higher capacity alternator which certainly helped.

Have you put a voltmeter across the battery terminals with the engine running? If it reads ~14 volts with all the stuff turned on, you are charging the battery. If not, you have a problem in the system somewhere.

With the voltage at the battery at ~14 volts, and the dash gage reads 11.5 volts, it sounds like you need a heavier wire to feed the dash to be able to handle the added current draw of the accessories, and still power the dash gauges. I would start there.

Good luck!

[EchoLodge]

guage

I have checked the voltage at the bat and it showed 14v with the acc on so I know its keeping up with the demand. I think the prob lies with the heater which drawls 8.5 amps by itself. I prob need to run a fused 10 guage wire to the heater and by pass the stock wire to which it is connected to. I did not see the inboard post. Adding the wire was per my mechanic. Thanks for the input.

[gn6027]

With the heater off (and blower, stereo, lights, etc. on), does your dash gage read ~14 volts (13-13.5 volts wouldn't surprise me)? If so, I agree that isolating the heater as you noted above should take care of it. If it still drops to 11.5 volts, there is still something else going on.

[EchoLodge]

volt meter

I might just run thicker wire to the stock breakers while I'm am at it. The stock harness looks like its only 10 or 12 guage.