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Komatsu D85 P21 1989 Fuse Location

NikinNZ

Member
Joined
Aug 25, 2025
Messages
18
Location
New Zealand
Hello all,

I have a 1989 Komatsu D85 P21 recently the dash console has not been lighting up (fuel, oil temp gauges etc), but with the ignition key on the fans/wiper etc still work but it wont start.

Is there a main fuse somewhere that i am missing, i have checked all the fuses located to the left of the drivers seat (up near the ceiling) but cant see any others? maybe one under the dash?


Still investigating but if anyone has any ideas it would be great to hear back.

Thanks from New Zealand.

Nik
 

Simon C

Senior Member
Joined
Jul 1, 2015
Messages
3,153
Location
Rocky Mountain House , AB., Canada
Occupation
Heavy Equipment Mechanic
Lots of Komatsu dozers of that vintage had fuse strips in the top of the dash in front of the driver. Top cover off and all inside.
Does it crank over or not when tried.
Have you tested the batteries and are all the cables and grounds good and clean.
That old must have some bad ground straps by now.
Is it powered by the S6D125 engine with separate heads or with a NH 220 Cummins engine.
Simon C
 

NikinNZ

Member
Joined
Aug 25, 2025
Messages
18
Location
New Zealand
Thanks Simon, the reply is much appreciated, i was working on it today, according to the plate on the engine the engine is a 6D14-1 . I am now not getting any power to the console (no fuel/battery/temp guags light up), i have checked all the fuses i have found and all OK. The batteries are brand new, there is power getting to the starter motor but doesnt seem to be any power getting to the ignition, but the fan/wipers etc work? when i click the light switches on the starter solenoid clicks rapidly and the lights flicker fast. I have checked the earth on the starter solenoid and cleaned it, no difference. I am thinking i may need a new starter solenoid? i will push on. But if anyone has any suggestions please let me know.

I am also trying to find a manual for one of these, or at least a wiring diagram....
 

epirbalex

Senior Member
Joined
Aug 5, 2017
Messages
710
Location
Akitio
Occupation
peasant
Thanks Simon, the reply is much appreciated, i was working on it today, according to the plate on the engine the engine is a 6D14-1 . I am now not getting any power to the console (no fuel/battery/temp guags light up), i have checked all the fuses i have found and all OK. The batteries are brand new, there is power getting to the starter motor but doesnt seem to be any power getting to the ignition, but the fan/wipers etc work? when i click the light switches on the starter solenoid clicks rapidly and the lights flicker fast. I have checked the earth on the starter solenoid and cleaned it, no difference. I am thinking i may need a new starter solenoid? i will push on. But if anyone has any suggestions please let me know.

I am also trying to find a manual for one of these, or at least a wiring diagram....

These guys have supplied me a few . Your dozer may have a separate manual for the motor and the dozer . When you turn on your key do you hear a loud clunk, quite a clunk but not the starter solenoid ? Somewhere behind your guages , not sure whats its called but by you key turn should power up a black box that powers every thing if it's wired much the same as my dozers .

This helps show how things are put together well , I couldn't find a match for you motor and dozer with the number of the motor you supplied .

 

Simon C

Senior Member
Joined
Jul 1, 2015
Messages
3,153
Location
Rocky Mountain House , AB., Canada
Occupation
Heavy Equipment Mechanic

These guys have supplied me a few . Your dozer may have a separate manual for the motor and the dozer . When you turn on your key do you hear a loud clunk, quite a clunk but not the starter solenoid ? Somewhere behind your guages , not sure whats its called but by you key turn should power up a black box that powers every thing if it's wired much the same as my dozers .

This helps show how things are put together well , I couldn't find a match for you motor and dozer with the number of the motor you supplied .

Think the engine could be a S6D140 series with independant heads or else I thought it would of had the S6D125 Series engine. I have overhauled both of these. Super expensive to repair but head gaskets last forever if taken care of.
Simon C
 

NikinNZ

Member
Joined
Aug 25, 2025
Messages
18
Location
New Zealand

These guys have supplied me a few . Your dozer may have a separate manual for the motor and the dozer . When you turn on your key do you hear a loud clunk, quite a clunk but not the starter solenoid ? Somewhere behind your guages , not sure whats its called but by you key turn should power up a black box that powers every thing if it's wired much the same as my dozers .

This helps show how things are put together well , I couldn't find a match for you motor and dozer with the number of the motor you supplied .

Thanks for the link, yes there is (or was a click) that has now stopped, there is a little black box behind the dash like this.black box 1.jpgblack box 2.jpg
 

Simon C

Senior Member
Joined
Jul 1, 2015
Messages
3,153
Location
Rocky Mountain House , AB., Canada
Occupation
Heavy Equipment Mechanic
Thanks for the link, yes there is (or was a click) that has now stopped, there is a little black box behind the dash like this.View attachment 353220View attachment 353221
That relay has a 86 terminal under beside the pins. It is the signal voltage that come from somewhere else. This signal power goes through a coil intrnally and out via pin 85 to go to ground. This actuates the large contacts to send major power from the #30 pin to #87 pin and out to whatever it feeds.
If it clicks that means the control signal side of the relay is working, does not guarantee the main power going into the relay at pin#30 is going out Pin#87. Contacts can get corroded or arced and power does not exit the relay. Even it it exits the relay, does not guarantee it is going to its intended path end.
Simon C
 
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