07 LR3 4.4L
I have 2 issues:
1. radiator fan always running
2. after car warms up for 15 min, i get a voltage spike to 17.5v. When the spikes occur, the cluster lights up like a Christmas tree, then goes out, "F" on dash, If I shut down the truck and restart all is ok for about 2 minutes, then the same issue occurs.
I think if I can solve where the voltage spike is coming from, all of these other issues will disappear.

What I have done;
3 alternators, all tested fine at 14+ v while running, changes PIG plug to alternator, new battery (12.7v), Clusterfix, TCCM sent out tested good, checked all grounds, new MAF, removed under hood fuse box, disconnected under glovebox fusebox, Checked sunroof drains, no water intrusion. , new brake light switch, rear bulbs, Car garaged it entire life, no corrosion. Lastly, sent in ECM and TCCM for testing. Tech said that the ECM circuitry was mint and tested fine but he could not test the ECM processor and if that is bad, I need to get a cloned unit. How can you test the circuitry and not be able to test the ECM processor?

Not sure what else to do any suggestions would be appreciated.

 

Where the alternators the same brand/source? If so, then you can not rule out even three being bad/wrong. Also alternators are model year specific, the LR3 V8, for example, has two different styles.

 

Both alternators are Denso and each seems to be putting out the correct voltage at idle (14.5-14.7) so i think i can rule out that part. Just changed the starter and cleaned the wire and connections but no change. Also just installed a new cloned ECM. Dealer worthless here, says its the alternator, changed it again but same problem, Brought it to another reputable LR mechanic, said he thought it was either the ECM or Cluster...both of which I have replaced.

over 6 months and I cant figure this one out.

 

That is actually a bit high at idle unless the engine is wicked cold and so are external temps. Generally 13.8 to 14.2 is normal. The only time I see over 14.5 is during negative temperatures on cold starts. The Alternator is controlled by the computer, as you know, but if the alternator is nor receiving proper inputs it defaults to full unregulated voltage. Thus I would very, very carefully inspect and test the three (or is it just two?) regulator wired going to the alternator.

 

I will recheck the PIG connector (2 wires) which i replaced from the alternator and report my findings. I have not yet inspected where that wire enters the loom of other wires...maybe there is a fray causing contact with another wire. thanks.