Alternator and cooling fan lights on.

[Karl_T]

So, I've just completed a dizzy refurb, and during the refit I did accidentally swap the plug leads over, got it all done and I'm about to go to work in it and these two lights are staying on.

Alternator is turning, no belt slippage, and if you pull the plug on the temp sensor the engine bay fan does spin.

Are there any fuses that may have gone, or a likely loose connection, or is it the alternator?

Open to any helpful diagnostic checks.

Karl

[mr2magic]

Use a voltmeter to measure across the battery terminals...anything less than 14v means alternator.

[PW@Woodsport]

I disagree with that as a diagnosis, it means it has a charging issue, it does not automatically condemn the alternator. In a lot of cases it's the wiring to the alt or main charging cable, it can also be a poor connection at the M2 or N1 connector corroded.

If i had a quid for everytime someone just fitted a new alternator when it wasn't the fault i'd be a rich man, i'm not saying it isn't the alternator but the wiring needs checking first before you reach that conclusion. In 20 years at least half non charging cars i've repaired have been wiring related.

Check charging rate at the battery as advised, if it is 12-13v then you have a charging issue. 13-14v is still charging to a degree but would put the light out if that were the case. The dash battery light and fan light (on the same circuit) go out when at least 13v is returned by the alternator on the yellow wire, anything below that and the yellow wire is just grounded by the alt, which lights the warning lamps.

Remove the 3 pin alternator plug, switch ignition on and check all three pins on the plug are showing roughly 12v, if one of them isn't then you have a wiring issue or fuse blown- check engine bay fusebox.

Check the main charging terminal power cable on the alt is secure.

If the above checks out, then and only then can you condemn the unit itself.

[Karl_T]

Cheers all. I've measured the battery voltage. 12.7 that dropped to 12.6 when the engine was running (and didn't budge when I revved it), I've also checked all of the fuses and they're AOK.

I'll go and check the plug voltages next.

Ta

Karl