Having an problem with my vRS, my only noticeable symptom is that after a of duration low engine revs, the fuel gauge develops a mind of its own, and rises up to around 1/2 a tank.

 

I think its related to the Alternator/Battery because once i rev the engine, it fuel gauge slowly settles to a correct value. Also after driving around for a while it seems to sort itself out, unless coasting where the issue reappears. 

 

I measured a the battery voltage in different states:

 

12.2V - Engine off (after a run)

13.3V - Tickover, minimal load

13.8V - Tickover with Heater Fan on.

 

I dont think its the Alternator as much as the battery, as it appears to work fine with high engine revs (i.e. alternator actually charging the battery). The Alternator Load wire appears to be intact too as the battery light shows on the dash when ignition is on, but the engine is off.

 

Any ideas?

 

edit: also a few cold mornings where perhaps its taken a bit longer to start, the dial has immediately gone to around 1/2 then the moment i rev to pull away it will drop down to the actual value.

They all sound low. Shouldn't you be seeing over 14 while charging a nearly full battery? And nearer 12.6-12.7 on a full battery with no load?

i thought over 14V too, but that would perhaps mean my Alternator is on its way out :(

Could it be the alternator load wire? As Dan says it sounds a little low on the engine off, but the rest are fine in my experience.

Reason I don't Think its the load wire jack is because the ASR light is not on and the battery light does go off when starting.

Reason I don't Think its the load wire jack is because the ASR light is not on and the battery light does go off when starting.

I'd suggest the alternator is on its way out.

I'd suggest the alternator is on its way out.

 

+1

Ok was hoping it wasnt but thanks all, looking like im swapping the alternator soon

I have about the same values, but with a 6year old battery.

Might be worth dismantling the voltage regulator/brush module off the back end of the alt, and seeing whether any of the connections are showing any signs of corrosion. On the Valeo version that I have, the outer black plastic cover comes off and then three hex-head M4s hold the reg pack on. All three of these fixings are also electrical connections (not the screws themselves, but you'll see what I mean if you delve in there, too tired to take piccies of my spare just now). Any moisture/age-related tarnishing may be affecting the function of the voltage regulator.  You can also check for suspiciously short brushes while you're at it.