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bcman
03-04-2017, 10:59 PM
I"m in dire need of some assistance. I just took the whole dashboard apart, which meant removing Fuse Block 1 as well as the instrument cluster. I was installing a camera system and external audio amp, so I tapped into the ACC switched power at the radio, and B+ constant under the driver's seat (I added another fuse block for these items, but left the fuses out for now). I just got the dashboard, instrument panel, and FB1 reinstalled, and tried to start the car to test if everything was still working. I inserted the key, and turned the ignition to position I. Instead of getting beeping indicating the door was open, I got a single beep when I got to position I. At position II, fuse 6 in block 1 blew, and I had no instrumentation. The engine will start, transmission will shift into gear, but I have no tach, speedo, fuel gauge, etc, and no turn signals or wipers. emergency hazard lights work. I've got climate control, but no rear a/c. I've tried replacing fuse 6, but it blows every time I get to ignition position II.

Any ideas? I'm supposed to be on the road to pick up my wife in 2 minutes :(

One call a/c
03-04-2017, 11:38 PM
You'll have to disconnect what you tapped into and see what you have from there.


Sent from my iPhone using Tapatalk

bcman
03-05-2017, 06:41 AM
So I disconnected the 4 power and ground connections I made this afternoon, and got a few changes: The single beep at Ignition position I stopped, and Fuse 6 stopped blowing at position II, although I still heard a 'pop'. Still no instrument panel, so I disconnected the instrument panel and cracked the case to see if the circuit board was fried. It looked fine, so I reassembled it and plugged it back in, and I got the door chime, and all the instruments came online! Everything was looking good. I reassembled the rest of the dash and drove to pick up my wife.

I heard a few more pops coming from under the steering column as I drove, but everything seemed to be working fine - turn signals, wipers, instruments. When I got to our meeting place, I checked under the dash, and found this:

http://i.imgur.com/nNVn2Lp.jpg

The previous owner had removed a trailer brake controller. This must have been the wiring for it.

The red wire was tapped into a black/red wire on the brake pedal switch:

http://i.imgur.com/Q7Znhsd.jpg

I though for sure this was the problem - a hot wire with an exposed end occasionally making contact with ground. I taped up the exposed ends, and the tap, and drove home.

But after about 20 minutes, another 'pop' and a visible spark from under the steering column, and the wipers and turn signals went out. I got home and checked fuse 6 - yup, blown again. I replaced it, and it immediately blew when I reached ignition position II. I even tried completely removing the wire tap and taping over the chink in the factory wire, but it's still blowing fuse 6.

What could I have done to short the wiper/turn signal circuit? Any ideas?

Aqua Puttana
03-05-2017, 01:27 PM
Fuse #6 is listed as Windshield Wiper Motor 20 amp.
https://sprinter-source.com/forum/showthread.php?t=24683


Did a wire get pinched to damage insulation?

Are all of the removed connectors back in proper places and completely seated?

Did a pin within a connector(s) get bent or otherwise damaged during the work?

:2cents: vic

bcman
03-05-2017, 04:15 PM
Fuse #6 is listed as Windshield Wiper Motor 20 amp.
https://sprinter-source.com/forum/showthread.php?t=24683


Did a wire get pinched to damage insulation?

That's certainly possible. my understanding is that most of the wiring for the turn signals and wipers is self-contained in Fuse Block 1. Any idea where I should look first for pinched wires?

Are all of the removed connectors back in proper places and completely seated?

I'm 99% confident they are.


Did a pin within a connector(s) get bent or otherwise damaged during the work?

That's also possible. I think I'm gonna check FB1 first, and also examine the relays there. I know one is for wipers and one is for turn signals.

autostaretx
03-05-2017, 05:57 PM
The bus bars that form the connections behind/inside Fuse Block 1 are notorious for breaking free from their plastic "restraints".

Perhaps that's adding to the circus?

--dick

bcman
03-06-2017, 03:15 AM
This morning I cracked open fuse block 1. Everything looked normal, although I have no frame of reference. But there were no loose pins or burn marks. I then got out the ohmmmeter to try to follow the flow of electrons through Fuse 6. I checked continuity with the left side blade for fuse 6 and each pin on connectors 2 through 5, and found it connects to pin 3 in connector 2. This matches up with the wiring diagram:
http://i.imgur.com/LlRRo11.png
http://i.imgur.com/ihYRJF7.png
I then tested resistance between the black/violet wire at pin 2 and ground, and measured 2 ohms. Does this seem normal? I imagine this could be the resistance of the motor winding, and 2 ohms is ~7 Amps, not enough to blow a 20A fuse.

autostaretx
03-06-2017, 04:46 AM
See the right-pointing arrow above the relay? That means that that circuit may go somewhere else, too (although they usually say where)

The black/violet is probably what powers the "park wiper" operation... if your blades are at the park position, i would think there would be infinite resistance between bk/vt and ground. (since the Home switch should be open)

--dick

bcman
03-06-2017, 04:52 AM
Excellent, I was dreading tearing apart the dashboard again to look for the needle-in-a-haystack that is a potentially pinched & grounded wire. But this is enough of a clue to motivate me to get back at it. I'll report back in a couple days.

autostaretx
03-06-2017, 06:21 PM
I agree with Vic that there could (now) be a bent pin in one of the many FB1/InstrumentPanel connectors...
(but that wiper ohm reading is really strange (if the blades are parked))

--dick

bcman
03-09-2017, 05:18 PM
Found it!

http://i.imgur.com/5KWv2E8.jpg

it was wedged up against the metal part of the dashboard. when pulled away, it measures infinite resistance to ground.

Now I just have to cut, re-solder, heat shrink, wrap a few layers of electrical tape for good measure, and reassemble the dash (more carefully this time).

Thanks everyone for your help!

bcman
03-20-2017, 05:40 PM
Hey Everyone,

I fixed the stripped wire, and re-assembly was a 99% success. Instruments, wipers, and turn signals all work as they did before the tear-down. The only differences are:
1. SRS light is on in the instrument panel
2. I ended up with 3 extra screws (the common T20 with captive washer) and these metal brackets:

http://i.imgur.com/EY9Y5Nv.jpg?1

I know they come from somewhere around the passenger airbag, but I couldn't find anything that looked right. The VA service manual and parts list are no help. Anyone have any guesses?

I wonder if the brackets act as some kind of ground for the airbag wiring, thus causing the SRS light. The wiring harness for the airbag has a symmetrical plug, so I tried it both ways, but the light is on either way.

Aqua Puttana
03-21-2017, 04:32 PM
...
1. SRS light is on in the instrument panel
...
During the work if any SRS component is disconnected (eg. - airbag) and the ignition key was cycled on the DTC will be triggered. Once it is triggered the SRS module proper must be accessed with a proper scan tool to clear the code(s). A general clearing of codes with a generic OBDII tool will not be enough.

Your SRS system may be ok now. It will require a proper reset or clearing of codes for the dash light to turn off.

vic