I have been having a few strange symptoms and need some help looking for the culprit. First, I started getting a whine from the engine compartment. Then the convertible top would stop working. You can hear the pump cycling but it seems not to have the power to open the top. After a few days of trying the top, sometimes the latch will let go and I have to help to top for the first foot or so, then it will open on it's own. When closing, it works fine but there doesn't seem to be enough power to close the latch. I have to do that manually.

I'm wondering if I may have a failing alternator. I took off the drive belt and started the engine. No whine. Since I have been doing a lot of work on the car, many of the parts are new.
I have replaced the water pump, Idler,tensioner and belt. The whine stays the same with ac on or off.

My voltmeter has at times been showing lower readings that I remember it doing. I seem to recall it was always center at 13. Now it shows lower than that at idle. I hooked up a multimeter to check the voltage. I was getting 12.4 with the engine off. Engine on and running around 1500rpm I got 13.4. If I let the engine idle I get around 12.20. Any thoughts?

 

When my alternator went on the fritz, I was getting a high pitched whine that I couldn't figure out what it was until it failed. The voltmeter was showing lower than normal as well. If you can drive it to an Advance Auto - they can test the system for free

 

The alternator in my XJ8 did the same whine before failing. I also don't think the alternator has any affect on the way your top is working. I think you should check the fluid level and condition and also check to be sure the by-pass valve has not vibrated partially open. It is a T-Shape rod on the pump.
Be sure that the fluid level is ok and the the fluid is in good condition and not beginning to gel up.

 

I took your advice and went to Advance. They did a check and it seems there is a problem with the alternator. At idle with ac and headlights on the voltage went down to 11.80. I may send the alternator out to be rebuild.

 

How old is the battery?

 

I'm thinking I may have two separate problems. My roof was not functioning when I bought the car. I found that the rams were leaking so I sent them out to be repaired. The systems was flushed with Pentosin fluid and the rams installed. It had been working fine until I noticed the whine. That's when I started having trouble with it. The petcock valve is closed and fluid level up to the top line. The joys of owning a Jaguar.