What should voltage say on scan guage?

BULBASOR

Active member
Bulbasor's factory battery went dead. I figure since he is a 2004 that was not a big deal, and for 140 bucks I replaced hte battery. All is fine, but just for the heck of it I decided to set one of my SCANGUAGE meters to monitor voltage. I notice that the voltage on Bulbasor according to the scan gauge is about 12.1 to 12.5 volts.

Is that too low?? Is the alternator going bad?
 

Aqua Puttana

Poly - Thread Finder
... I notice that the voltage on Bulbasor according to the scan gauge is about 12.1 to 12.5 volts.

Is that too low?? Is the alternator going bad?
That is low. I would expect you to see 13.6, maybe 13.8 to 14 volts after first starting, and then tapering off to the low to mid 13 volt range after some driving.

It could be the alternator, but it could be a bad connection or something else. Most battery shops can easily check the alternator output.

vic
 
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icarus

Active member
If you are seeing voltge in the 12s after running for a bit, it is too low. You should see charging voltage 14 vdc+, float in the high 13 range.

Icarus
 

autostaretx

Erratic Member
Dead alternator could/would explain your dead battery....

My 2005's original battery shows 12.4v when left overnight
13.4 to 13.9 when charging/running along the highway (varies with speed/load (lights,etc))
Drops to 11.smidge during the starting cranking (i pre-start the ScanGauge to have the VLT showing before turning the key)
For reference, i have the 115 Amp alternator.

Is the alternator hard to replace?
There are a number of threads discussing it (with photos).
One quirk is that there's a *slight* asymmetry to the alternator housing that requires it be placed with a Vee-notch against the engine. If you get it in "upside down", you can't fully tighten the belt.
ALL posters agree: buy a real Bosch alternator, not a 3rd party "equivalent".
(also, the broken part could be the over-running clutch in the alternator's pulley, or the mounted-on-back diode and regulator assembly, not necessarily the alternator itself)

--dick
 
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Aqua Puttana

Poly - Thread Finder

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