I just put a new dash/gauge assembly ,wire harness, and fuse/relay in the truck. This was all MIA when I got her. I double checked all connections went to start and turning over but no start. Checked the panel and have 24 volt on the 12 volt lug. New batteries installed and 12 and 24 volt at those wires in the box. Any ideas? I hope the engine computer did not burn up with 24 volts.
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Lmtv1078A1 24 volt on 12 volt side
- Thread starter pangea
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Disconnect your batts something is def wrong. Start at the batts make sure installed properly. move on to the polarity box under the spare tire, after that the power cables go along the frame and around the pivot and into the cab. Check at the alternator make sure the outputs are not swapped by accident. 12 and 24 volt cables come up under the passenger dash and go to the panel make sure they are not switched.
OK, so batteries connected properly, alternator 12 and 24 OK, polarity box 24 volts on 2 upper lugs and 12 volt on two lower lugs. On the fuse panel the 24 volt and 12 volt wires are correct. If I connect the 12 volt to fuse panel only the 12 volt side gets power. But if I connect 24 volt to its proper lug the whole panel gets 24v (with or without the 12 volt wire on) and some lights on the led dash readout come on and so does the transmission selector pad without ignition switch off. With 24 volt temporarily connected to the panel I pulled each fuse and relay one at a time to try and isolate it to no avail. All wire connection numbers correspond to each other. Am I missing something ?
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Maybe you are somehow bypassing one of the two large relays under the panel. Those relays have wires to the panel. Maybe a pair of relay leads accidentally got switched when swapping the panel. Here is a pic of where they go.
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How do you know you got all the dash connections correct? 24 volts should be switched by a 12 volt circuit activated by the dash power switch. Illumination should go thru the light switch if that's off and illumination is coming on maybe theres a short somewhere. What year and model is the truck? Are you sure the batts are in correct. 24v is closest to the frame 12 between the batts and negative furthest out.
OK, the dash lights coming on are the warning lights on the display and not the gauge lights. When I switch the ignition switch to on the rest of the display lights come on and I hear relays being energized. The truck is a 2001 A1 cat3126. Thank you superman. happy new year everybody. Signing out. Tomorrow I shall start quadruple checking all again.
coachgeo
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Dash or parts of it I believe is 24v. Maybe that is confusing you?
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He has stuff powering on with the switch off
coachgeo
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uhhhh. now dats not good.
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Is there a breaker you can pull to de-energize 24 volts to that circuit?
I pulled all the breakers and fuses and did not change issue. With all the fuses and breakers out I still had 24 volt on 12 volt side.
I then proceeded to pull the plugs on the panel with breakers and fuses out and found J307 plug had one wire #1674 that showed 24 volts on voltmeter.
With the plug#J307 pulled and relays and fuses installed I now can turn ignition switch off and I have no Trans key pad light on or warning lights staying on and when I switch it on all normal lights come on and is ready to start. "YEA" So I belive I isolated it.
I need a copy or file on the A1 series trucks to figure out where wire #1674 goes .
I traced the wire into the main bundle that goes behind the heater to dash or body plug but there are so many white wires.
I then proceeded to pull the plugs on the panel with breakers and fuses out and found J307 plug had one wire #1674 that showed 24 volts on voltmeter.
With the plug#J307 pulled and relays and fuses installed I now can turn ignition switch off and I have no Trans key pad light on or warning lights staying on and when I switch it on all normal lights come on and is ready to start. "YEA" So I belive I isolated it.
I need a copy or file on the A1 series trucks to figure out where wire #1674 goes .
I traced the wire into the main bundle that goes behind the heater to dash or body plug but there are so many white wires.
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Maybe a switch at the dash is not connected properly and power is feeding back thru it. The manual is electronic it has specific troubleshooting but I have not found wiring diagrams that can be printed out or laid out unfortunately.
side it would be about $300 if authorized
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The A1 manual is only on computer. No pdf files. I wish there was a paper schematic I could lay out on the table and work thru.
coachgeo
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someone put schematic for A1 up in the TM's forum of this board not too long ago. Actually came across that this was done by accident. Posted link a month or so ago but here it is again. May not be enough of the the schematic.... but hope it helps and a big thanks out to whom ever got it into a PDF form and posted it there
http://www.steelsoldiers.com/showthread.php?158229-FMTVA1-Electrical-Schematics
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That makes life easier. Saved a copy for myself.
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Those A1 schematics are nice, actually. Once downloaded to your computer, expand the page to match your eyes (in my case, BIG) and look on SHT (sheet) 2 in the description column for the circuit you want to find. I haven't found a way to search for the name of the circuit, except manually, but that does not take long. Once you find the circuit you have trouble with, go to the 'sheet' number, find the 'location' number, then slide down the page to the label for that circuit. For example, the A1 flasher unit is on SHT 8, location 213, and slide your cursor straight down to near the bottom of SHT8 to see A1. Those 'location numbers' are printed across the tops of the sheets.
There are many wire numbers on the schematics, plug and pin numbers, and of course all relays and switches. Need to look at the switches on the steering column switch? Find it on SHT2, called 'S3', and then check the three SHTs it is spread out on.
For this particular problem, for the OP, I'm looking for J-307 and wire 1674 and have not found them yet. Maybe a group effort would help out!
By the way, you "A0" guys with earlier trucks, the whole set of schematics have a common grid system, X and Y, just as if you laid them all out on a table, not X-y repeated for each sheet.
There are many wire numbers on the schematics, plug and pin numbers, and of course all relays and switches. Need to look at the switches on the steering column switch? Find it on SHT2, called 'S3', and then check the three SHTs it is spread out on.
For this particular problem, for the OP, I'm looking for J-307 and wire 1674 and have not found them yet. Maybe a group effort would help out!
By the way, you "A0" guys with earlier trucks, the whole set of schematics have a common grid system, X and Y, just as if you laid them all out on a table, not X-y repeated for each sheet.
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