Don't trust dash voltage gauge (VDO 86+)
04-17-2002, 09:48 PM
#1
Burning Brakes
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Don't trust dash voltage gauge (VDO 86+)
Well, I was starting to think my alternator was dying, turns out that it's just my VDO gauge reading incorrectly. I took some measurements at the battery, 13.5v with lights on, a/c pump running (although low on freon). The gauge on the dash shows about 12.3 volts. The funny thing is in the morning the gauge reads about 13.7 volts but later in the day after the car has sat at work for 8 hours, when it's hot (about 90f lately), the gauge reads low. Does it make sense that my gauge reading is varying with temperature?
04-17-2002, 10:56 PM
#3
Nordschleife Master
Your alt is going to put out less voltage the hotter it is. Because of diodes being hotter as well as the voltage regulator is designed to drop voltage a bit so as not to cook the battery in hot fast recharges.
As far as higher reading at battery than at dash gauge, that is normal from less than great grounding and the fact that the positive feed from battery to fuse board is too light weight. Take a reading at the dash gauge with a real voltmeter and you will probably notice the same thing going on.
As far as higher reading at battery than at dash gauge, that is normal from less than great grounding and the fact that the positive feed from battery to fuse board is too light weight. Take a reading at the dash gauge with a real voltmeter and you will probably notice the same thing going on.
