parasitic draw from alternator?

2006 E250 4.6, 350k miles. camper van. It has started to develop a dead battery if it sits for a couple of weeks. No changes made to anything electrical.

Multimeter reads .83 mA then settles down to .71 mA of draw. Cold cranking amps don't drop below 10. Auto parts store tested it and tells me the battery is fine, but that the diodes on the alternator are failing (voltage regulator is fine apparently). It sounds like the diodes failing could be the parasitic draw, is that correct?

Vehicle runs fine, though it does have a bad HG which it has had for over a year. What can I expect as it continues to fail other than the battery being drained?

I don't want to put much money into this vehicle due to mileage and HG issue, but it may be worth putting a new alternator in. 

Yes, a failing diode can cause a draw.

Are you sure it isn't 0.71-0.83A? Less than 1mA of draw is background noise and less than I'd expect of even an '80s car.

A bad diode can cause parasitic draw though. Check the fuse diagram and see if you can pull one to cut power to the alternator while the car is parked as a test.

I'll double check, it could have been A instead of mA.

And thanks for the tip, I'll see if I can pull a fuse and see. 

Just disconnect the charge wire from the alternator and put your mm in the circuit.

If it shows a draw, there you go.

In reply to ShawnG :

Good idea, thanks. I'll have to see how easy it is to access. These Econoline vans don't have a lot of room.

I'm not familiar with late model Fords, but you may be able to simply replace the diode pack in the existing alternator instead of spending the $$ for a whole new one.

Vans were created to punish mechanics.

In reply to stuart in mn :

Good to know, I'll look into that.

Yeah I need another elbow to work on this thing. I might pay to have it done. Shop rates are $85 around here in NE MO. Seems worth it.

stuart in mn said:

I'm not familiar with late model Fords, but you may be able to simply replace the diode pack in the existing alternator instead of spending the $$ for a whole new one.

Yes, but a reman alternator is likely $50 and 30 minutes to replace, while a diode pack is $40 and requires a full teardown of the alternator.

In reply to Curtis73 (Forum Supporter) :

I looked at Rock Auto.  Amazingly they do list a couple remanufactured alternators for ~$50 on closeout, but most are between $100 and $150.  It didn't appear that the diode pack was available separately for this truck, so it's a moot point.  My response was based on experience with other cars where the diode pack is available for $5 or $10, which is why I suggested it.

The last rectifier I looked up was the same price as a reman alternator, but that was for an E30.

So today I pulled the positive cable from the alternator and nothing, no apparent draw. I've couldn't find anything online saying which is the alternator fuse. Airbox was all I had to remove to access the alternator. 
 

With the alternator + unplugged, I measured the battery again. Still .80 amps. I'm now thinking it's not the diodes. Dang.