EX100-2 keeps blowing 1A fuse #5 - I'm stumped

[Dayton]

It was running good, had a brand new EC. All EC functions worked. I started cleaning up the wiring and ziptying things, cleaned some mud/dirt from around the harness where it enters the cab and now when I go to start it, #5 fuse blows. I assumed it was a short around that area but I can't find anything. It's a 1 amp fuse for the "EC Power Signal On" Hope I didn't fry this new computer.

So far I tried:
Unplugging PVC - no change
Unplugging EC motor - no change
Unplugging white wire at alternator - no change
Unplugging body module - no change
Unplugging main harness connector in the cab - still blows the fuse
Checked wiring from fuse panel to EC connector #39 and #26, no short to ground. No voltage. (Good)
Checked wiring from I think it comes from the key to the fuse box, 25 volts with key on.
EC Board itself has no smell or discoloration anywhere still looks new.
I get about 2.8 ohms from the fuse box (No fuse EC side) to a ground when it's plugged into the EC

Is there any way another circuit is interfering with the ground after the EC to allow too much current through when the EC is trying to power on? Anything else I can disconnect to see if it's stealing ground and drawing too much amperage through? The harness is a nightmare to get to under the cab, I'd like to pin point the spot if it's that. Thanks

 

[mg2361]

Hope I didn't fry this new computer.

Fingers crossed. Hopefully nothing bigger than 1A was ever used on that circuit. If it was, then the PVC would be damaged, but repairable.

Typically that fuse blows when there is a short circuit in the 5 volt reference circuit to one of the sensors. However, you unplugging the PVC and still have the fuse blowing eliminated that.

Checked wiring from fuse panel to EC connector #39 and #26, no short to ground.

Unless you disturbing the wiring broke the connection to ground. Did you perform a wiggle test of the harness while trying to check for a short to ground?

 

[Dayton]

Fingers crossed. Hopefully nothing bigger than 1A was ever used on that circuit. If it was, then the PVC would be damaged, but repairable.

Typically that fuse blows when there is a short circuit in the 5 volt reference circuit to one of the sensors. However, you unplugging the PVC and still have the fuse blowing eliminated that.



Unless you disturbing the wiring broke the connection to ground. Did you perform a wiggle test of the harness while trying to check for a short to ground?

I never had anything larger than a 1amp fuse in there since getting the new EC luckily.

Are you saying that even though that fuse is for the EC, there may be an issue with a circuit on the PVC? As in the PVC is drawing power from the power signal on for the EC circuit after the fuse and EC?

I tried wiggling the harness and putting in another 1amp fuse every so often but it always blows. Is there another way to do the wiggle test?

 

[Dayton]

Fingers crossed. Hopefully nothing bigger than 1A was ever used on that circuit. If it was, then the PVC would be damaged, but repairable.

Typically that fuse blows when there is a short circuit in the 5 volt reference circuit to one of the sensors. However, you unplugging the PVC and still have the fuse blowing eliminated that.



Unless you disturbing the wiring broke the connection to ground. Did you perform a wiggle test of the harness while trying to check for a short to ground?

I'm not sure what circuits or grounds I should be checking since it's not clear what fuse #5 circuit is after the EC on the wiring diagram.

 

[007]

I am completely un familiar with your machine.
But speaking from experience when presented with things like this you must move foreword trying to do least damage as you went.
First step would be to push a small festoon bulb into the position of the fuse and go do and intensive wriggle test watching the bulb.
Use clips to to attach a small globe on wires to the fuse holder if you cant see it where you are working on the wiring loom.
When the short is removed the bulb will go off or glow dimly.
If it is the blade type fuse break open the top of a blown one and solder the globe wires to blades.
If you are forced you can cut that wire in the middle of its run and figure which side the short is and so on.
Its not the end of the world to rejoin the cut wire if its done properly and you can usually find the fault quickly without making a mess of the loom.
I am old school and like to solder wires back together, no crimping connections in looms for me.

 

[Dayton]

I am completely un familiar with your machine.
But speaking from experience when presented with things like this you must move foreword trying to do least damage as you went.
First step would be to push a small festoon bulb into the position of the fuse and go do and intensive wriggle test watching the bulb.
Use clips to to attach a small globe on wires to the fuse holder if you cant see it where you are working on the wiring loom.
When the short is removed the bulb will go off or glow dimly.
If it is the blade type fuse break open the top of a blown one and solder the globe wires to blades.
If you are forced you can cut that wire in the middle of its run and figure which side the short is and so on.
Its not the end of the world to rejoin the cut wire if its done properly and you can usually find the fault quickly without making a mess of the loom.
I am old school and like to solder wires back together, no crimping connections in looms for me.

I tried the bulb and wiggle test with the PVC and the EC unplugged, then the pin from the plug to the EC to a ground. I didn't want to put the bulb alone in place of the fuse incase it fries the EC.

The fuse pops instantly when the key is turned on with just the fuse.

 

[007]

The highest inrush of current was already the fuse fault current so a bulb should not affect EC
The low current of a bulb would not cause any component heat build up.
If a semiconductor in the EC has failed it cannot get much worse.
Is the fuse blowing with the EC disconected?

 

[Dayton]

The highest inrush of current was already the fuse fault current so a bulb should not affect EC
The low current of a bulb would not cause any component heat build up.
If a semiconductor in the EC has failed it cannot get much worse.
I the fuse blowing with the EC disconected?

Okay I'll try a bulb in place, maybe see if I can also add the fuse after to be safe. When the EC is unplugged it does not pop. My old EC plugged in doesn't pop it either, but not sure if that helps since that one doesn't work at all. I've narrowed it down to something in the EC or downstream. It's not clear what is downstream since the EC feeds all sorts of circuits.

 

[007]

Fuse is not required as current cannot exceed bulb on state.
Can you not start unplugging all down stream items?

 

[Dayton]

Fuse is not required as current cannot exceed bulb on state.
Can you not start unplugging all down stream items?

I suppose I can, there is alot of things to unplug but I suppose that would be the next step after the wiggle test.

 

[007]

I would unplug active sensors first and leave the passive ones.
So all the three wire sensors which the EC might send power out to.
Any Control devices that require power from the EC.

 

[Dayton]

I would unplug active sensors first and leave the passive ones.
So all the three wire sensors which the EC might send power out to.
Any Control devices that require power from the EC.

Okay some new information, I tried the bulb with a 1 amp fuse inline. Fuse doesn't pop. EC turns on now, buttons all work machine starts. Emergency relay or shutdown relay on the side trips sometimes and cuts power. Needed to turn key off and on to get EC working again.

Smelt electrical burning, inside new EC tripod capacitor right after the pin is slightly discolored but I think still working. Turned the key on quick and felt it, the capacitor heats up quick. Too much current is going through I have a short somewhere after the EC. Can anyone tell me how to narrow down the short now. I'll start unplugging the connectors but is there ones in particular I should be looking at first?

 

[007]

Capacitor does not make sense.
Can you post a photo to the component you say is heating up quickly.
Would be good if i can read the part number on it.

 

[Dayton]

Capacitor does not make sense.
Can you post a photo to the component you say is heating up quickly.
Would be good if i can read the part number on it.

 

[007]

picture is not visible?

 

[Dayton]

picture is not visible?

Should work now sorry. I just about unplugged everything and it is still heating up

 

[007]

em11 to em13 i would have thought would have been for noise suppression and are VERY surprised that has failed.
That is probable it is trying to self heal and could be applying an intermittent short to the main VCC on the board.
I would expect to see a three terminal regulator some where that would be supplying field sensors and it should be red hot if there is a overload in the down stream wiring.

 

[Dayton]

em11 to em13 i would have thought would have been for noise suppression and are VERY surprised that has failed.
That is probable it is trying to self heal and could be applying an intermittent short to the main VCC on the board.
I would expect to see a three terminal regulator some where that would be supplying field sensors and it should be red hot if there is a overload in the down stream wiring.

Everything else on the board looks okay, the 4 voltage regulators don't heat up at all or have any burning. This tripod capacitor at EM13 is connected right to the pin on the EC that comes from the 1 amp fuse blowing (power signal on) I get 38.7 ohms from the pin to a ground when unplugged through the board. From the middle leg of the capacitor to a ground I get 0.1 ohms. I'm not sure how the board works but maybe it's shorted internally? Maybe the middle leg is suppose to be grounded and it discharges to the third leg?

 

[007]

I had a quick look on the internet and they can be custom so not sure what is in it.
i might be straight capacitor, might be over voltage clamping, the list goes on.
If you can read numbers of the un burnt ones might give you a lead.
You could steal one from your failed board also if you are skilled with soldering iron.
If it is straight in on the VCC rail from fuse you might just be unlucky and the fault not be that sinister.
A HV shock to the system might have taken it out or just bad component.
It is unlikely that something down stream in the board would cause that to fail like that or be causing more issues.
You sure 4V regulators as 5V is very common.

 

[Dayton]

I had a quick look on the internet and they can be custom so not sure what is in it.
i might be straight capacitor, might be over voltage clamping, the list goes on.
If you can read numbers of the un burnt ones might give you a lead.
You could steal one from your failed board also if you are skilled with soldering iron.
If it is straight in on the VCC rail from fuse you might just be unlucky and the fault not be that sinister.
A HV shock to the system might have taken it out or just bad component.
It is unlikely that something down stream in the board would cause that to fail like that or be causing more issues.
You sure 4V regulators as 5V is very common.

I meant 5v, but I have 4 of them. Here is more.pics