View Full Version : 94 d90 electrical problem

03-22-2009, 02:41 PM
The 30 amp maxi fuse for lighting blows when the battery is hooked up. I checked continuity of brown wire to rear of relays and it seems o.k. but some of the others are showing continuity also including the black ground wires ? Does this brown wire splice in with others could it be shorting somewhere ?

03-22-2009, 07:30 PM
If the fuse is blowing even before you turn ANY lights on, then it sounds like you have a short in the line FROM the maxi fuse to the fuse block above the tunnel, inside the cab. If it were in one of the individual lighting circuits, the smaller fuse for that circuit would blow first.

The MAXI fuse for the lighting circuit is supposed to be 60 AMP, not 30. In fact all are 60, except the EFI Fuse, which is a 30AMP fuse. I'd suggest putting the correct fuse in before you dig too much further.

03-22-2009, 08:17 PM
I'm pretty sure thats the original fuse but I'll try a 60 tomorrow. Do you know where that brown lead from the block goes directly? It seems to me it must be spliced to the others that go to the relay block. Can anyone post a wiring diagram please? thanks.

03-23-2009, 10:23 AM
You're correct, the lighting fuse on the 110 is 60 AMP, however the 90 is 30 AMP.
I've scanned the page(s) from the shop manual. Let me know if you need more, but it looks like the wire OUT of the MAXI is brown and goes to the headlight switch BEFORE individual dash fuses, and given that the headlamp switches on these trucks are known for failure, I guess that's where I'd start.

Well it looks like the website won't let me upload them and they are so small now, I can't resize.
Post a fax number and I'll fax them to you.