I have a 2001 Discovery II with a curious electrical issue. When drawing too much power (lights, ac or operating windows at the same time) the 3 amigos will come on, the radio will go off and on and sometimes it will go into power save mode in the transmission. I have replaced the battery already. Any ideas?

Thanks,
Joe

 

Bad ground? Corroded cables?

 

Could your alternator be failing?

 

Could be all of the above. One way to examine is to buy a volt meter, attach to battery terminals. At idle, should see 13.8 to 14.4 volts, nothing extra on. As more things are turned on (wipers, head lights, AC, inside fan) the volts will drop, but should remain above 13.2. Yours may be going low becuause alterantor is dying (you can meter from big brown wire in fuse box, which is from alternator). You also could have corroded or oxidized connections, at big amps it does not take much. Would want clean battery terminals and studs, the wires in the under hood fuse box (large ones ), any bolted in fuse links should be tight, and follow the black battery cable to the chassis ground point and make sure that is clean and tight.

However, on the alternator side, if volts drop rapidly below 13.2, say when lights, AC, and wipers are on, the alternator is likely at fault. It has a series of diodes inside that change the three-phase AC into plain old DC. If one diode is blown, it makes max amps 66% of normal. You can have a vehicle that cranks, charges battery OK, but kills battery on rainy days when head lights, wiper, and AC defroster are on at same time. A D2 has a 130 amp alternator, and a D1 is a 100 amp. My D1 draws about 85 amps with everything stock running.

You can also have charging system checked for free at a parts store.