Is the alternator supposed to have a constant output?

[MFB]

or will it hunt up and down as a bad idle hunts up and down?

I'm reading 13.8 volts at the alternator on startup (between the B+ and ground terminals), dropping to 13.5 volts when it warms up, but it oscillates plus or minus 0.2 volts with the up and down idle. I'm reading 13.7 at the battery at 900 rpms, but again it's not steady.

Is the alternator supposed to put out a constant 14.4 volts?

I'm wondering whether the up and down voltage at the alternator is cause or effect. Enquiring minds want to know.

MFB

73 inka

91 318i silver

[Guest Anonymous]

No big deal... Ideally you want to be @ 14.4 however I doubt you have a BRAND new alternator, voltage regulator, wires & battery.... anywhere around 14 is fine. The key is to put the car at a low idle with the lights, heater, wipers, radio, etc all on and make sure that you don't drop down below mid 12 or else you have charging issues.