battery light on - alternator stuffed?

**wally** · 14th June 2008, 05:31 PM

My battery warning light has come on (Def 300Tdi). The battery had been allowed to go dead flat after having a light run from it for some time. After having been put on a charger it is now showing 12.5V. With the engine idling this drops to about 12.2V. The same voltage is showing at the alternator. It comes up when the engine is revved but it's difficult hold a voltmeter and rev the engine at the same time so not sure how far it would come up. So I'm assuming the alternator is stuffed. But before I take it off and send it to an auto elec...is there anything I should check? To complicate things slightly I have just recently fitted an engine watchdog and EGT gauge. I took the power for both of these from the green wire on the third fuse, the one that supplies power to the temp and fuel gauges. The battery light has only come on since I fitted them (and the temp and fuel gauges are both playing up, ie. reading low, and fluctuating). Is this coincidence or have I done something? I'm a bit confused here. Any suggestions would be most welcome.

**langy** · 14th June 2008, 10:01 PM

You've partially answered your own question - disconnect the EGT and watchdog, and see what happens. You should see 14v at the alternator.
If, after doing the above you don't see more than the 12.5v (ish) then check to see that the other two connections for the alternator are OK - you may have inadvertently blown a fuse somewhere.

You may have tapped into the circuit for the indicator light - which would explain a lot.

**MacMan** · 15th June 2008, 08:41 AM

Also, if all your battery will hold is 12.5V, it's well on the way to ****et. A healthy charge is somewhere between 12.7 and 12.8V.

**MacMan** · 15th June 2008, 08:47 AM

I find it hilarious that the forum software censors the name of a place in Thailand that starts with Phu and ends in ket.

**ladas** · 15th June 2008, 10:21 AM

Originally Posted by MacMan

I find it hilarious that the forum software censors the name of a place in Thailand that starts with Phu and ends in ket.

Mind you given what goes on in that place that starts with Phu and ends in ket - maybe we shouldn't be surprised

**Pedro_The_Swift** · 15th June 2008, 10:28 AM

Originally Posted by MacMan

I find it hilarious that the forum software censors the name of a place in Thailand that starts with Phu and ends in ket.

If Ron has his way That place in Thailand will be renamed "banana"

**wally** · 15th June 2008, 02:10 PM

Originally Posted by langy

You've partially answered your own question - disconnect the EGT and watchdog, and see what happens. You should see 14v at the alternator.
If, after doing the above you don't see more than the 12.5v (ish) then check to see that the other two connections for the alternator are OK - you may have inadvertently blown a fuse somewhere.

You may have tapped into the circuit for the indicator light - which would explain a lot.

OK, I disconnected the pyrometer and engine watchdog and it has made no difference. I've also put in a brand new battery. Again, no difference. The new one, by the way, is also showing 12.5V while the engine's not running. Start the engine and it drops to 12.2. Revving the engine makes no real difference. The wire I spliced into supplies power to the fuel and temp gauges and, as it turns out, the indicators. I used this circuit because that's what is recommended in the Thermoguard instructions. "The recommended supply point for Defenders is fuse 3 in the passenger compartment fuse box, the existing instrument supply fuse. A switched 12Vdc supply from the ignition switch arrives at this fuse on a white wire and supplies the original fuel and water temperature gauges on green wires. Splice the red wire of the EGT power lead to one of these green wires using one of the supplied IDC connectors." That's exactly what I did and I used it for the engine watchdog as well. There is only one green wire there and that's what I used. All connections on the alternator seem OK. So... What might I have done? I've checked all the fuses in the passenger compartment, and the three big ones in the engine bay near the firewall. All are OK. Are there any others I don't know about?

Or is this a weird coincidence?

**rick130** · 15th June 2008, 02:15 PM

I wrote ***** the other day, as in "to p*r*i*c*k* something" and it was censored !

At least it's better than a US based forum I'm on, whenever I try to write A$ to differentiate from the US$ it censors it !
Oh, and 'hell' and 'damn' are damned there too, but us Aussies can get away with the correct spelling for ar$e, so go figure.......

**wally** · 15th June 2008, 04:56 PM

Originally Posted by rick130

I wrote ***** the other day, as in "to p*r*i*c*k* something" and it was censored !

At least it's better than a US based forum I'm on, whenever I try to write A$ to differentiate from the US$ it censors it !
Oh, and 'hell' and 'damn' are damned there too, but us Aussies can get away with the correct spelling for ar$e, so go figure.......

Yeah but Rick what about my little charging problem. Come on, you're a clever man.

**langy** · 16th June 2008, 12:12 AM

I've dug out my RAVE for defenders. and according to it, you're correctly attached the EGT/watchdog - and it's nowhere near the indicator lamp. You'll have to pardon my comment about the fuse and connections to the alternator, as I was thinking Disco, and the defender is way simpler.

There is only two connections on the defender alternator - output and field

Provided that the little brown wire with the yellow stripe is feeding power to the alternator during running, and there is still only 12v (ish) at the big brown wire, then it's time to take the alternator to the auto electrician.

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