Fluctuating voltmeter readings

**miked** · August 31st, 2012 09:31 PM

anyone else with the same problem?

voltmeter (Circuit brand VMG 12V) is tapped to cigarette lighter socket. grounding point shared with other gages on the metal frame of dashboard.

problema ay nagflfluctuate ang reading from 12 - 14 volts and sometimes lower than 12. one time, nagzero reading. took readings with a digital tester also at the same point where voltmeter is tapped. ganun din nagffluctuate. pero battery reading is 13.74 - 14.4 volts kaso hindi ganon kagrabe fluctuation at the battery.

any inputs appreciated.

**oj88** · August 31st, 2012 11:36 PM

Wires will always introduce a certain degree of voltage drops. Especially if there's a lot of current passing through it.

That is what's happening in your case. The cigarette lighter socket practically shares the same wire coming from the battery to power up all electrical and electronic accessories in your car. The more electrical load being used, the lower the voltage is across the +12V wire. In geek speak, that's Ohm's Law at work.

You typically get a more stable voltage when you get the reading directly off of the battery posts.

**kinyo** · September 1st, 2012 01:32 AM

one time, nagzero reading

indicates loose connection/contact somewhere

**glenn manikis** · September 1st, 2012 07:32 AM

loose connection or maybe the carbon brush of your alternator is nearing the end of its life.... OR IC problems...

sir did you flood ford your car?

**Retz** · September 1st, 2012 10:11 AM

might be the alternator or you might using a high load in your car that causes the voltage to fluctuate

**miked** · September 1st, 2012 12:19 PM

Originally Posted by oj88

Wires will always introduce a certain degree of voltage drops. Especially if there's a lot of current passing through it.

That is what's happening in your case. The cigarette lighter socket practically shares the same wire coming from the battery to power up all electrical and electronic accessories in your car. The more electrical load being used, the lower the voltage is across the +12V wire. In geek speak, that's Ohm's Law at work.

You typically get a more stable voltage when you get the reading directly off of the battery posts.

salamat sa lahat ng replies.....i was also thinking na mataas ang resistance offered by the wire. pati kasi sa ignition terminal lower by about 1 volt than batt voltage. but at least mas stable ang voltage readings sa ignition terminal kesa dun sa lighter socket. radio is also tapped to the same wire where lighter is tapped. bale inisplice ko lang voltmeter connection dun.

di rin dinaan sa baha. yung mobile undercarwash lang sa highway kadalasan pero may protective splash pad naman sa sides ng engine compartment. tsaka 1 year pa lang nung nagpalit ako alternator at carbon brushes.

nakakaantok pa naman magsphagetti (wiring). parating mababa ang ulo.

**miko101130** · September 1st, 2012 05:56 PM

sakin sir i tapped the 12v supply from the ignition line under the dashboard tapos solo niya yung ground area na kinabitan ko, very
stable naman using also circuit brand nang volt meter...

pero eventaully i repalced it with a raizin voltmeter and stabilizer na naka attach to the batter poles.... digital kase eh mas accurate.. hehehe...

**miked** · September 1st, 2012 09:56 PM

tried wiggling the main harness loom under the dash and it is indeed a loose connection. nagffluctuate ang voltmeter reading. pero sa dinami dami ng sphagetti di ko na makuhang isa isahin kung nasan. inilipat ko sa ACC terminal after the main switch with a 5 ampere fuse yung connection ayun naging stable kahit na iwiggle ko yung harness.

problem lang is napakainit yung dash lights nya. buti nilagyan ko ng sariling switch yung gage lights para patayin at lumamig. will find next LEDs that will fit. bili na lang siguro ako ng mga LED lights (yung pinaplug sa lighter) sa mga accessory stores tapos kakarnehin ko n lang kung wala yung direct bolt on.

**miko101130** · September 2nd, 2012 12:06 PM

tama ka sir, LEDs dapat yung gauge light sa likod.. pag regualr bulb mga 5-10watt yung power kaya mainit, samantalang sa LEDs less than 1 watt, cool na cool.

**Chinoi** · September 23rd, 2012 04:33 PM

Originally Posted by miked

anyone else with the same problem?

voltmeter (Circuit brand VMG 12V) is tapped to cigarette lighter socket. grounding point shared with other gages on the metal frame of dashboard.

problema ay nagflfluctuate ang reading from 12 - 14 volts and sometimes lower than 12. one time, nagzero reading. took readings with a digital tester also at the same point where voltmeter is tapped. ganun din nagffluctuate. pero battery reading is 13.74 - 14.4 volts kaso hindi ganon kagrabe fluctuation at the battery.

any inputs appreciated.

Possible loose connection sa screw ng metal ground. Linisan mo lang uli ang metal part at add another awg #12 ground sa ibang ground wire connection.