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No bus no start

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Old Jan 28, 2019 | 06:24 PM
  #1  
Chad Durham's Avatar
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Default No bus no start

I have a 99 XJ and the blower motor stopped blowing tracked down the problem to the blower relay was melted along with the wire going to the blower motor fixed that it works great now. After I got done with that went to start the jeep it would turn over but not start it says no bus and none of the gauges work no radio. I'm just lost I have checked all fuses and they are good any help would be great
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Old Jan 28, 2019 | 07:28 PM
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I'm concerned that you might have messed up the ground for the dash. It can cause the symptoms you mentioned (including taking out comms bus) You didn't by chance have to remove any dash bolts from down along side the foot well did you? (about shin level).
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Old Jan 28, 2019 | 07:40 PM
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No didnt mess with any grounds besides the one to the blower motor
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Old Jan 28, 2019 | 07:43 PM
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Do you still have the glove box out? Because another thing that could take out the ground is if there is something pumping positive voltage onto the dashboard framing that is normally grounded. You would think that would pop a fuse if something was shorting. But considering so much dash functionality is off line, I'm doubtful this is coincidence. If you haven't already, consider pushing the wire work around a bit, and disconnecting the relay/connectors you worked on to see if it changes the behavior.
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Old Jan 28, 2019 | 07:51 PM
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The relay for the blower motor was melted on I think it was number 36 which is the hot to the blower the wire was melted a little also so I cut in town passed the melted part and replaced it in new wire and relay plug off a parts jeep could that wire be melted on down and melted into ry he ground wire. I don't know where its grounded though
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Old Jan 28, 2019 | 08:11 PM
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I would want to take a test lamp hooked to a known positive, and test for ground on the dash framing.

These guys chased a similar problem with missing comms bus and no start problems (and it was kicking their butts until they figured it out). Look at 31:00 if you want to cut to the chase:

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Old Jan 28, 2019 | 08:22 PM
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Alright thanks it's at a friends house and I'm home so I'm goin to go mess with it tomorrow and I'll let u know tomorrow if I figure it out
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Old Jan 29, 2019 | 05:35 PM
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I tried to upload a video but wont let me. With the blower motor off I can unplug the pcm connector closest to the grill and my electric fan turns on and relays click turn the blower on and unplug the same 1 and it does nothing
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Old Jan 30, 2019 | 10:42 AM
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Did you ever check for continuity to power and ground on the metal of the dash?
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Old Jan 30, 2019 | 03:37 PM
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Yes I borrowed a power probe from a friend and all grounds are reading 0.0 so there is no feed back with blower motor on or off
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Old Jan 30, 2019 | 04:39 PM
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Ok, your radio only needs a positive and a ground to work. So use your power probe to figure out which of those 2 things is missing. That will give a direction.
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