KZ1-TE Alternator Fault Diagnostics (1 Viewer)

[MR Will]

Hi All, I have a 1997 UK spec j95 which has been in the family since new and I have been doing some jobs on it over the last year to get everything back to how it should be whilst also using it as my only car.

The current problem is an electrical one which I am less confident on so it has got me a bit stumped. Yesterday I drove for approximately 2 hours with the headlights on and towards the end of the journey the batteries were discharged to the point the dashboard warning light came on. The warning light turned off at higher engine speed or driving with all headlights switched off.

I put a voltmeter on it today firstly with the engine off I found that both batteries were at 11.8v. I then tested the terminals on the voltage regulator which were 11.4v for the ignition, 11.6v for the Sense, 11.2 volts for L. With the engine running, on the battery terminals I was getting 11.4v at idle (900rpm) and 11.6v at fast idle (1100rpm).

I had previously removed a damaged 7 pin caravan socket which was connected into the ignition wire of the voltage regulator. At that point I cut and rejoined that wire. That was my first thought for the cause but it seams to be passing a voltage so I am less convinced now.

The alternator is original so could be the issue but is there anything which I can do to confirm the problem before I think about replacing anything? Any thourghts would be greatly appreciated!

 

[KiwiBogan]

The usual suspects....

Check the tension on the alternator drive belt(s). They might not be done up tight enough. I like to do mine up so there's about 15mm of flex. Tight but not too tight. Don't be fooled by seeing the alternator spinning at idle and assuming the belts are tight enough. I got tricked with that recently on my 100 series which had the same symptoms you're experiencing. Actually feel the tension of the belt by hand.

Go over all the engine earth points, check for tightness and maybe give them a clean if they look rough. Battery Earth to engine block. Battery Earth to Chassis. And from memory theirs another earth from the starter motor to one of the transmission/engine bolts? Less likely to be that last one as the car is starting fine by the sounds of it.

Failing those two options, I would isolate the starter battery, inspect for visual signs of a failure like swelling of the walls and just general aging/wear. If it's showing signs of physical damage (actually looks old and knackered), it might be best to replace it. Otherwise, connect up a battery charger and give it a good charge over night. Then the next morning, put an element type load tester on the battery and see how it holds up. The alternator needs good battery voltage in order to function. If the battery seems to be good and holding charge, you've basically narrowed it down to the alternator being stuffed and needing replacement.