Dear All,

My '95 XJR has been playing up again. The last few times I have driven it, the oil pressure gauge, and sometimes the warning light has worked intermittently. This morning, on the way to the train station, the demister fan slowed down and I noticed that the voltmeter had dropped to around 11 volts instead of the usual 14-15. It then recovered and the fan sped up again. This happened again as I approached the carpark but to the extent that the battery discharging light came on. I parked the car and caught my train but I am worried how it will behave on the way home, only about 10 minutes away. The car is not used that regularly nowadays and it has been very wet for a few months in the north of England, so I wonder if water has got into the electrics somewhere. I guess it would take a significant drain to pull down the voltage like that. Given the intermittent nature, do you think it could be a faulty alternator?
Any advice appreciated.
Regards,
John

I'd have the Alt checked, be aware the harmonic balancer is an issue on our cars and as they delaminate they will affect the Alt's ability to provide proper out put.

I had a problem where the intake manifold began to leak and I would get a dip in power every 32 seconds at idle. My voltmeter dipped as well as the tachometer, occasionally resulting in a stall.


I didn't experience any dips while driving the car, only when engine was warm and at a stop light.

I would check the belt tension first, I ve had this happen once or twice in the past,

I agree with dagny, check the belt tension first. I have experienced exactly the symptoms you describe, and a tightening of the belt sorted it.

Thanks Gents,


Luckily the car started and I was able to get home before the battery ran out. The behaviour was consistent, with the voltmeter reading about 11 volts and the battery drain light coming on unless the revs where kept above about 2.2K, in agreement with reduced output from the alternator. Increasing the revs further did not increase the reading on the voltmeter. I could not hear any squeaking from the belt or damper but will mark the crank pulleys, SC, alternator/water pump and ac, and see if they move relative to each other this weekend. If not I will remove the alternator and see if I can get it tested.

It might be a connection problem. You mentioned wet weather in your first post, and corroded charging and ground connections could act up in wet weather. Especially the engine to chassis ground.

I had the same problem with my xjr where battery light came on intermittenly ( not sure about the fan tho). Anyways i end up crawling under the car, took out the undertray and while inspecting the alternator i realize the connection was loose, so all i did was plugged it back in tightly and the problem went away.