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'90 VDP voltage drain

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Sprocket

Sprocket

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My problem:

The battery drains down to a no start condition is not run daily (or at least every other day at the outside) and I have to stick a charger on it to get it up to proper voltage.

I tested by pulling each fuse one by one and measuring for draw. No smoking gun found.

Looking for some other ideas or known issues that may cause this.
Car is a '90 VDP Majestic with about 62K on it.
Battery is new.

thanks
 
Computers will draw them down, as will keep-alive for radios.
Alarms.

2 days......not a big draw, but enough.

Alternator. Not protected by your small fuses.
Boot lamp staying on.
Bonnet lamp?
Glove box lamp?

You have an ammeter?
Might be interesting to see what the actual drain is at the battery.
Then unplug the alternator and start going down the line unplugging and re-plugging until you find it.

Remember the First Rule of Auto Repair, which states:

"Just because it's a new part doesn't mean it's a good part."

Don't just assume the battery is okay.

If it was mine, I'd charge the battery (or run the car), disconnect a batery cable for 3 or so days.......then re-connect and try to start it.

If the battery is dead (or too low to start), and it was disconnected, ain't the car......
 
The "normal" drain is about 52 millamps or around a half an amp. A relay will pull about 120mA, and it can go from there.Check the antenna, and trunk light. The other thing that used to cause things like this was the micro switch in one of the front door handles for the lock heater. Since the drivers door gets used the most, I would check that first. Get a copy of the service CD from Jaguar. That will have copies of the really good, better than the shop manual wiring diagrams. Worth their weight in gold.
 
Take a close look at the wiring diagram. Both myself and a frind have had a similar problem with battery drain. Mine on a 90 XJS V-12 and my friend on a 94 XJS 6 cyl coupe. There is some wiring for trailer connections in the main harness, but it uses different fuses on different years and models.

Start by pulling fuses one at a time, let the car sit for a couple of days and see if it is resolved. Start with the fuse for power aerial and then one by one repeat the process until you find the circuit with the drain. Then you will need to trace the wiring with the wiring diagram looking at the wires for signs of chaff through or pinch through for the insulation. Most of the fuses will supply more than one circuit, so it will take a while to find the culprit.

My friend traced his to the unused wiring for the trailer light wiring that he never used. No trailer hitch was ever installed. He found a way to supply power to the two other items fed off the same fuse. Mine is in the power aerial circuit, but exactly where, I have not solved.
 
thanks guys. The biggest issue is it's my mom's car and I don't get over there daily. I will give it the batt disconnect test first, but it did it on the last battery too (which is why we have a new one).

Her mechanic had the car for a couple of days (he's a jag only mech, ex dealer guy) and he couldn't find it. He said he pulled the fuses one by one, but you know, he might not have done any of that either, but he's pretty straight up so I figure he did.

I'll have to go through the car at a fuse a week or so :smile: It might have to do with the interior lighting, cuz sometimes you get the bulb out warning light, but all the interior bulbs work? I'll try with that one first.
 
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