nzporsche944s2

Hi guys

What voltage reading are you getting on the dash. Last night driving with headlights and foglights on and radio but nothing else (no rear demister, no fan, etc) the dash gauge was reading around 12V and occassionally dipping just below 12V. Tonight I will put an altmeter across the battery terminals to see if the gauge is accurate.

I "thought" that the output of the altenator should be around 14V and that the regulator controls the current to prevent over or undercharging? Is it possible my regulator is on the way out? Any test procedures?

Justin S2

My S2 used to read 12V and then I cleaned all the grounds when I had my engine out and changed my voltage regulator, which was probably 3/4 worn and now it reads ~13.5-14V.

kbull

The voltage gauge in my S2 will fluctuate to a slightly different value each time I drive the car. Each time it stays roughly the same for the duration of the drive, but it displays a slightly different value almost every time I start it. This can range from about 12.6V - 14.4V. I think it might be a grounding issue primarily, possibly a problem with the voltage regulator too. I bought an IceShark full grounding kit from a guy on Pelican and I hope installing that will solve this issue for good.

nzporsche944, I would do what Justin S2 did and clean all the grounds and maybe replace the regulator. That should help to improve your voltage readout.

nzporsche944s2

Bumping this thread - so I replaced the Voltage Regulator. The old brushes were definitely worn so no harm done changing them however the voltage output hasn't changed. It's still putting out around 12.6 volts.

I've got the ground locations from this chart. Which grounds should I start with? I would guesss the ones on the chassis rails / bell housing? Then the one by the battery?

Would a failing battery cause a low output or reading?

ArcticSteve

Replace the negative battery cable that runs to the top of the bell housing. Not saying that will fix it, but it's a must do before anything else. There is also a secondary wire running from the negative post. Good shop can make one for $35 (both wires plus connector).

nzporsche944s2

ArcticSteve - thanks for the reply. My car is Right Hand Drive so the battery is in the left rear compartment behind the left rear wheel wheel. I guess my equivalent of what you suggest would be the negative cable to chassis - MPVII in the diagram above?

ArcticSteve

NZ:

In that case I would replace that and also the clutch bell housing ground cable to wherever that goes.

Mark944na86

Get the multimeter out to read the voltage across your battery terminals -- don't rely on the dash gauge. The volatge should vary depending on the state of charge of your battery... when it is fully charged you should be near 14.0V. If you have everything on (lights, fans, etc.) and the battery is not charged it might get down to under 13V . Also note it can take a minute or so for your alternator to put out the steady voltage after starting up (it will read low initially). Revving the engine to 2500-3000 will get it up to charging voltage faster.

The factory regulators on the alternators are actually set to 14.0V. I changed mine to a 14.5V regulator of the same form factor and that keeps the charging a little happier I've found. Another way of compensating to some extent for increased resistances in older wiring. 13.8-14.2V is considered optimal for charging a normal lead-acid 12V battery.

If you have a "calcium" battery (still lead-acid but with calcium replacing antimony), you might find putting it on a "smart" trickle charger helps -- I also do this. Calcium batteries won't fully charge on a older style alternator charging system alone, apparently (they will charge up to about 85% capacity, but to get the last 15% or so you need to get a smart charging system to finish it off.)