View Full Version : AWD eating 20amp ECU fuses
Skapper
29-02-2016, 02:41 PM
As the title suggests my AWD has developed a taste for 20amp fuses. This is fuse number 15 of the engine bay fuse box.
I've blown two recently. But worse still its melted part of the fuse box - around the fuse socket.
No recent addins or electrical mods, no recent bumps, crunches, smoke or driving through flood waters. I misdiagnosed the last fuse dinner as a distributor. I cannot see anything obvious. The car is up and running on a fresh fuse, though I've disconnected any 12v accessories... That's about all I can think off.
The most recent fuse blow out sent the two TCU relays off (clattering away at a million clatters be minute).
Any ideas, as always are much appreciated. Thanks.
Hmm, leaking heater core? What else is on that fuse?
Skapper
29-02-2016, 07:04 PM
Not sure what else is on that circuit, but I'll look into it, thanks.
Though, no coolant smell in the cabin.
Your comment has reminded however that I did have the ECU out - for the Ralliart tune - a few months ago. No visible signs at that point.
The other odd thing worth mentioning is that the fuse only seems to nuke itself at home. Which is handy. But, its never fried whilst driving or when I'm out and about. It has always seemed to make it home just in time. You pull up in the drive way, shut it down, but it will have fried the fuse between then and when you go to start it next.
Were those drives with a/c on? Moisture condenses on exposed wire on the ecu fuse line after a drive? Also, there is meant to be a moisture shield above the ECU, was this removed or damaged when you last removed the ECU?
Just had a look at the wiring diagrams for the TL AWD. It appears fuse 20 is also used for the A/T ECU. It goes to the A/T Control Relay (B-59). The Engine ECU also has a control relay (B-103) between the fuse and ECU. I would check both relays.
Skapper
07-03-2016, 06:29 PM
Vlad, thanks for the input. Sorry for going dark, busy here.
Here's an update and further information.
It ate its first fuse prior to the ECU being pulled. At that time the weather was ridiculously hot. AC was on.
The second fuse it ate after the ECU reflash. This to me says the fuse addiction is not related to the ECU tune, and, possibly not due to me being ham fisted during the removal/reinstallation of the ECU.
No coolant or moisture spotted during the ECU removal or install.
The weather on Sunday just gone was torrential rain. The car had been driven to and from work in this weather for the week, and clocked up a bunch of km's while my youngest son learns to drive. The thing was swimming in water for at least a week.
However, Sunday it ate a fuse thirty metres out of my driveway... then another as I franticly tried to limp it home. Again, the fuse is completely melted away - nothing left of the yellow plastic. The plastic around the socket, in the fuse box, is melting.
Prior to this, after fuse No. 2, I had disconnected all 12v accessories. So I'm pretty sure it's nothing that I have plugged into the 12v socket.
I've replaced the two relays - ECU and AT control relays with second hand parts to confirm the original relays must still be good.
Tonight I had a poke around in there again, trying to find anything in the engine bay, and centre console area. Nothing obvious beside the fact the shift lock cable had come off the transmission shifter. The split pin is gone. I have no idea how that happened, but assume I may have done it at some point. Reconnected/pinned that.
There have been no electrical mods to the car aside from the 12v accessory mod, an LED in the dome light and some new rear speakers.
I cannot seem to pick any action or event that triggers the fuse to blow.
Tonight it did a lap of the block like nothing happened.
Hmm. Has this ever happened at night with headlights on? Have you checked the regulator? Although if the regulator is on the way out, it should have affected circuits with lower amp fuses first.
Here is a curve ball for you. Did you find the original pin? If not, could it be rolling around somewhere in the centre console area and randomly making contact between two electrical connections?
Edit: just noticed you did a night drive. During your night drives, have you ever noticed the lowbeams flaring? I had a situation in my KW where the alternator was dying and at night, the low beams would randomly flare up to be brighter than higbbeams, blinding once9 m8 ng traffic. Did not realise it was the regulator until it killed my LED break light bulbs.
Madmagna
08-03-2016, 04:43 AM
I think you may have issues in the box itself, the area is melted giving the impression of heat. You have a bad connection, this causes heat.
I would be looking here before anything else
Skapper
08-03-2016, 01:11 PM
I think you may have issues in the box itself, the area is melted giving the impression of heat. You have a bad connection, this causes heat.
I would be looking here before anything else
Thanks Vlad and Mal.
I've casually kicked the idea around at work - I work with electricians - and they've said to replace the fuse box regardless as the damaged connection (at the fuse) will make any problem worse.
If I get a chance today, I'll do some proper investigating.
Skapper
12-03-2016, 11:59 AM
Well. I got a new fuse box... for the unbelievable price of $20.
However. The wreckers just cut through the accessible part of the loom leading to the fuse box. I dont see how this now just "plugs in" to my car. I have an entire fuse box with about six inches of severed loom hanging out the back of it.
I have the option of getting the part myself, and I get the feeling I'll have to go get another one. Do I need the whole engine bay loom or anything to replace the fuse box? Or, is there some magic way of connecting the replacement fuse box to the car?
MadMax
12-03-2016, 12:12 PM
As Mal suggests, the melting of the fuse may be due to a poor, high resistance connection on the underside of the fuse box rather than excessive current, or something is loose under the fusebox and shorting out randomly.
Seeing you have a $20 'new' one, complete with some wiring, have a look how things are arranged there, look at the box in your car, and compare.
I've had heat build up on an inside fuse box before, melted stuff but it was just a spade connector on the back that needed a bit of an extra crimp with a pair of pliers.
Skapper
12-03-2016, 12:24 PM
I just tried pulling apart the fuse box. THAT, to me, is not an option. Pretty sure I need a whole loom to do this.
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