Do!nk

I recently found a burnt fused link that made my electric fan stop working (on my '88 f150 xlt lariat 5.0). I cut out the fuse and temporarily wired it together without the fuse and the fan worked fine, switch it on/off at the dash like it should. Two days later, truck won't start and battery is dead.
I trickle charged it for 20 hours and only got 3V when battery was tested with multimeter.
The extra wire (from the battery) for the fan is a constant draw and shows the same 3V as the battery terminal to terminal. Help!?

BTW, I tried to jump start it from another vehicle and I got nothing. It was like the other vehicle wasn't even there (red to red, black to black) and I got no fire at all from the truck. Not even the annoying ding ding when the key is inserted.

fltdriver

You are running it through a relay correct?

Also, when jumping a vehicle the "good" vehicle should be only hooked to + battery terminal, - grounded to frame or engine block, "dead" vehicle should be hooked to + battery terminal and - battery terminal. This eliminates the chance of frying anything on either vehicle.

Chris_1

iTrader: (1)

Try cleaning your connections - battery, solenoid, starter, ground. And if you're going to hook up a "hot wire" like that put an inline fuse in. Fuses are there to keep from burning things out (or the truck to the ground).

Chris_1

iTrader: (1)

If your inline fuse cooked, there's usually a reason. Something is drawing more power than those wires can handle. I wonder if you might have a dead short in that system that's draining the battery (also what cooked the fuse ?)

Do!nk

Could one wire draw enough power to prevent a jump start?

fltdriver

Definitely, pull the wire and I bet you can get it jumped no problems. Probably shorting somewhere so needs checked out.

Never answered my question though, you are running your controls through a relay? If yes try unplugging the relay and testing the wire again, sometimes the relays will fry and cause all sorts of hassles. It takes 1-2 minutes to pull the relay and retest so I recommend doing that first.

Chris_1

iTrader: (1)

And clean your connections

Do!nk

A medium gauge (Red) wire runs from the positive battery terminal, behind the radiator, to a spot between the radiator and the coolant tank. There is a relay there and the switch from the dash connects to a heavy gauge orange wire that goes into the relay - that orange wire is where the melted fuse used to be.
I cut out the fuse and wired it directly to make sure the electric fan worked. Since the test, I haven't run the truck. If I stab the red wire 2-3" away from the battery and connect to a ground, I get 3V running through the wire with the ignition off.
If the relay is faulty, will a parts store give me what I need if I bring in the dead relay?
I bought a fusable link which I will wire in when I get the dying battery sorted out. The battery was new in 6/13 and the alternator has always charged it. I cleaned the battery terminals and all wires before I started troubleshooting and everything was conducting OK.

fltdriver

First off, fuse goes between battery and relay, not switch and relay. Pull (or disconnect) relay from harness (or however it connected-pull female plugs off of male prongs) and test the wire from battery. If it's still pulling current your power wire is grounding somewhere. If it doesn't have current then the relay is allowing it to pass current. Swap another relay in (any one from the truck will work), if it still pulls current then the relay isn't the problem.

Edit: if you can help it don't buy relays from parts stores, they are WAY over priced. Go to a junk yard, pull a part, or salvage yard and grab some relays from any vehicle, the newer the better. I usually snag a handful when I go and pay $0.50 to $1.00 each. The factory relays will usually outlast replacement cheap ones 2-3 times over.

Do!nk

This may seem really dumb, but where would I find an easy relay on my truck to test with? Well, I yanked the relay and it was still drawing power. Entering the relay is a red and yellow wire, exiting is black to ground, orange to e-fan and green to dash switch, if that matters.
So I pulled the red wire off the battery to eliminate the power suck and hooked up a charger. With some good luck, I may be able to crank it tomorrow, then sort out the wires.