My '88 302 Econoline Automatic discharges the battery quite quickly with the key out. After recharge there is quite a bit of current loss as indicated by a small spark when I touch the battery ground terminal to the negative post. I hear a small relay clicking when I do this. I am alone, so can't find the exact relay, but it seems to be under the dash on left side.
When I turn the key to second position I get about a one second buzz and then the Check Engine light comes on. No other dashboard lights come on. Another thing I notice is that the engine will not idle down.


What to check next? I seem to remember something similar when a diode on my alternator went out, but the alternator I have in is almost new.

Hal in ND

 

Get a multimeter, set it to amps mode. Install the multimeter between the battery and the positive. Pull fuses one at a time until the multimeter reads current draws of less than 3/4ths of an amp or so. It will take about 45 minutes, and will get you down to one system causing the problem.

 

thanks! Hit the jackpot on Fuse 8, a 15a for dome lamp, map lamp, 4.9l cooling fan relay (don't have 4.9l), and Radio memory. Was losing 2.5 ma when in and it dropped to 0.1 ma with fuse removed.

This is a Waldoch van so there are lots of dome lights and two moveable map lights. Should I now try operating these switches a few times in case there is hidden corrosion or begin by taking out bulbs?

 

mA or Amps? 2.5mA is not killing your battery, though thats too low to be plausible. Personally i would pull the light assemblies out of the trim/holes, and disconnect them one at a time while checking the meter between disconnects.

After that i would also pull the radio and disconnect the harness in case the radio has gone to crap and shorted. But pulling the radio means pulling a CRAPLOAD of the dashboard (all the trim on the drivers side, the ashtray, the kick panel, the driver side kickpanel steel plate, headlight switch, 12v socket, etc.)

My standard spiel with conversion vans (and why I dislike them so much) is that you cannot be sure what is actually done to the wiring/hvac. You could have a wire rubbing on the body of the van somewhere behind the headliner causing a high resistance short somewhere. You could have something completely unrelated to lights connected to that fuse. Who knows. You have eliminated 90% of the potential problems, but you managed to pretty much find it on one of the largest (in terms of distance) circuits on the van.

Edit to add: Also, being the idiot i am. You didnt have the doors open while testing this did you? If they were, the lights were drawing power as they should, and the relay was the dome light relay for the door switches. You will also get a spark if you have a hood light on, etc. I would get the battery/alternator tested as well. Its free at autozone, and may eliminate that problem.

 

I've made that same mistake before, you're not an idiot. He'll figure it out I bet with the info you've given him.