Battery Voltage going crazy high
02-02-2015, 08:16 PM
#1
Staging Lane
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Battery Voltage going crazy high Hi all,
I left my '98 Formula parked all weekend in the cold and upon returning to it my battery voltage gauge is sporadically surging and swinging past 18 volts. It randomly returns down to normal ~13volts then randomly surges back up to 18+. When it surges high the cluster goes wild and the headlamps surge in brightness.
I've got it in the garage now with the battery disconnected but I'm not exactly sure what to look for. The alternator and battery are 6 months old (worth mentioning the alternator was a refurb, they didn't have a NIB in stock).
Any ideas? My only thoughts were a loose connection causing a short or possibly a bad voltage regulator. I've got a multi-meter handy, is there anything I can measure to eliminate some possibilities?
Thanks all
I left my '98 Formula parked all weekend in the cold and upon returning to it my battery voltage gauge is sporadically surging and swinging past 18 volts. It randomly returns down to normal ~13volts then randomly surges back up to 18+. When it surges high the cluster goes wild and the headlamps surge in brightness.
I've got it in the garage now with the battery disconnected but I'm not exactly sure what to look for. The alternator and battery are 6 months old (worth mentioning the alternator was a refurb, they didn't have a NIB in stock).
Any ideas? My only thoughts were a loose connection causing a short or possibly a bad voltage regulator. I've got a multi-meter handy, is there anything I can measure to eliminate some possibilities?
Thanks all
02-05-2015, 11:39 AM
#4
did you reconnect the ground strap from the alternator to the body?
what generally causes high voltage output from the alternator is a bad voltage reference to ground, the voltage regulator knows it's suppose to maintain 14.5 volts at most in relation to ground, but if your ground connection has resistance then that causes system voltage to go higher. so if it's not a clean connection of the alternator frame to ground, then inspect the output wire from the alternator into the wiring harness where it splices in. because you or someone did work in the engine bay, odds are bad connection somewhere, can also be bad battery cable where the end screws into battery wiggle bend them while engine idling to see if it has an affect. if all of that doesn't help then get a new alternator, the internal voltage regulator in your reman'd unit is bad which is not surprising.
also, the voltage reg inside the alternator is a microprocessor and it's suppose to sense problems then just stop the alternator from outputting at all. then that one wire in the 4 pin plug gets connected to ground through the alternator, telling the PCM there's an alternator charging problem and turning on the check engine light. If you have no check engine light and alternator DTC, just wild fluctuating volt gauge then it's most likely a bad wire connection.
what generally causes high voltage output from the alternator is a bad voltage reference to ground, the voltage regulator knows it's suppose to maintain 14.5 volts at most in relation to ground, but if your ground connection has resistance then that causes system voltage to go higher. so if it's not a clean connection of the alternator frame to ground, then inspect the output wire from the alternator into the wiring harness where it splices in. because you or someone did work in the engine bay, odds are bad connection somewhere, can also be bad battery cable where the end screws into battery wiggle bend them while engine idling to see if it has an affect. if all of that doesn't help then get a new alternator, the internal voltage regulator in your reman'd unit is bad which is not surprising.
also, the voltage reg inside the alternator is a microprocessor and it's suppose to sense problems then just stop the alternator from outputting at all. then that one wire in the 4 pin plug gets connected to ground through the alternator, telling the PCM there's an alternator charging problem and turning on the check engine light. If you have no check engine light and alternator DTC, just wild fluctuating volt gauge then it's most likely a bad wire connection.
02-08-2015, 10:11 PM
#5
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I would read the voltage at the battery, sounds like a bad voltage regulator. Any car will have small voltage fluctuations depending on load and engine rpm. Should vary between 13.2-14.5v when engine is on. It will always be lower at idle when engine fans are on and ac is on, and be closer to 14v when cruising on the highway for example. Voltage spikes over 15v sounds like abad diode/regulator which is part of the alternator. I would be cautious in buying a remanufactured alternator, some are junk and some are ok. Just make sure you buy from a reputable brand with a real warranty.
