KOMATSU D20S STARTER PROBLEMS

[rslawson]

I would love some insight as to what my problem is. I just replaced the starter on my loader. My loader is D20S-5 Model 50540. I had to replace the starter because a wire came off of the relay on the old starter. After I replaced the starter I tried to start it and I am getting nothing. Not a click, not a slow start... nothing. I jumped the starter yesterday to make sure the starter was good and it started right up by jumping. After I got it started I shut it back off but I noticed the starter and the starter solenoid both were HOT!!!! I mean super hot. Questions are :
What would make them get so hot?
What would not allow me to the starter to turn over after installing the new one. Battery Voltage is fine. Is there a diode on the alternator that could cause these issues? I can't find any schematics on this loader anywhere. I am guessing the relay attached to the starter solenoid is the safety relay tied in with the alternator. Would a bad diode on the alternator allow the starter to jump start and get super hot like it did? I am scratching my head here. Thanks in advance!!!

 

[DMiller]

When you 'jumped' the starter, how did you do it? You need to start checking voltage from starter button or toggle into the next solenoid down to the starter itself, make sure it is wired correctly and that there is no constant voltage to the solenoid to make it hang engaged. The only way it will get hot is for the Bendix to remain engaged and allow the motor to be driven by the engine which will lead to failure of the starter motor. The 'relay' on the alternator is the regulator for the charging circuit, it won't hang the starter in, at most it would drain the battery over a few hours.

 

[rslawson]

I used a jumper wire to go from the wire from the battery to the small screw on the solenoid. I marked them with a red line. I took the alternator off to get the voltage regulator off and the inside of the alternator was full of dirt. I attached pictures of the alternator, jumper wire and regulator. I attempted to "jump" it again to raise the bucket so I could access the alternator. When I tried to jump it today all it did was make a "click" sound and the starter did not engage. I am going to have the alternator inspected and rebuilt. Would the alternator cause it not to start? It will not turn over. I turn the key to start it and all that happens is the 2 red lights on the dash turn on. When I turn the key to start it nothing happens. What is the relay on top of the starter beside the solenoid? That relay comes from the alternator correct? That is how I got to the alternator as the problem. I hope I haven't burnt up the solenoid/safety relay already. I can't upload my photos of how I jumped it. I have a piece of large gauge copper wire about 6" long with alligator clips in each end. I placed one clip on the wire from the battery on the starter and I placed the other wire on the small wire that comes from the relay on the solenoid.

 

[rslawson]

Here are the photos

 

[Delmer]

I don't know why it got hot in the first place. The alternator would cause it to not start the second time if the battery was dead, put a charger on it and see how many amps it takes, then try to start it again when the battery is charged up.

 

[rslawson]

I have the alternator off of it now to be tested. The only way I can start it is by jumping it with the wire from the battery on the starter and the solenoid wire. I tried that today and it wouldn't jump start. I bought this thing a year ago and I haven't been able to use it at all because everytime I get something fixed something else breaks. Idk what is wrong because I could start it and run it prior to this issue without any problems. One of the wires on the safety relay broke off of the original starter the same day I had finished changing the seals in the lever that controls the bucket. I don't think the guy I bought it from rigged it up to sell it but it certainly is starting to feel that way.

 

[rslawson]

Are you saying I should try and start it without the alternator on it? If my problem is within the alternator then it should start if the batteries have enough charge. Correct

 

[Delmer]

Correct, as far as I know. But the Japanese have been known to do some funny things with starter wiring. Make sure the big wire to the alternator is insulated, not sitting there bare, it's hot all the time.

 

[rslawson]

It is insulated. I tried starting it with the alternator off of it and it would not do anything. There are 2 small wires coming off the "R" terminal on the alternator. One of them appears to go to the pigtail the relay on the solenoid plugs into. I am going to take the alternator in and see what they say. I tried to "jump" the starter earlier and it did not turn the motor over. I put my battery charger on the batteries and have it on 2Amp slow charge. Going to let that ride for 24 hours and see what it wil do. I think I am going to take the starter in with the alternator and have them both tested. That way I will know they are both good when I put them back on. If that doesn't fix it I will find a local mechanic.

 

[DMiller]

The alternator is a false hope but it needs to be functional for keeping the batteries up, there will be a relay between the key or rotary switch and the starter motor it will be suspect at this time, if the engine was run for any length of time before noticed the starter getting hot the batteries could have been drawn down but doubtful where the starter motor could be fried. Only way it could get hot is to have remain engaged and the engine pushing it, that generally wipes out the armature.

With everything connected you need to access the rear of the start switch, verify power is there if not then the feed from the large stud to the switch is disconnected or a fuse link or fuse failed. If power there turn switch to start position and verify the output terminal comes hot, trace that wire to the relay package and verify which relay it feeds then verify the relay line has battery feed and the relay engages(clicks) ten check for output power.

 

[rslawson]

Thanks for your help DMiller. I will verify voltage at the switch and trace out the wire. I am going to trace out the wires on the relay as well. It just baffles me because it would start right up everytime prior to the starter going out. When the wire broke off on the relay on the old starter it was the constant hot wire on the relay. The only way I found it was I could see the arc where the wire had voltage on it and it was touching metal when I would turn the key to start it. I guess it has caused something to blow down the line. I have to find it.

 

[rslawson]

Ok see if this makes sense to you.....
The starter is off the machine. I had the key turned to the ON position only to check for voltage issues on the machine. I can hear a ticking sound like a second hand on a clock. The big wire attached to the starter began to smoke( all this is with out the machine started or trying to start it). I immediately turned the key off. As I was walking around the machine I could smell something that smelled like it was burning. As I was investigating I noticed the negative post on the 1st battery was smoking. I disconnected it. I made sure all the wires from the alternator were not making contact with each other or anything else. Any ideas? Again all this with the alternator off of it and the key in the on position only. Machine not started.

 

[DMiller]

Starter is probably locked up, the engage plate inside the solenoid most likely welded to the studs and as you turned the key on gave it hot to cause the short cooking situation. Check the starter motor if will turn with fingers, will need a ohm meter or continuity tester and check from the motor stud to the batter stud of the solenoid, will tell if still connected across.

 

[rslawson]

Ok Thank you DMiller.

 

[rslawson]

I used my ohm meter and I rang out the batt wire and the wire on starter and I didn't have a closed circuit. I did however have a closed circuit when I touched the starter wire and the bolt that holds the starter relay.

 

[DMiller]

Solenoid has to ground, how many ohms resistance were there starter term to ground bolt? If less then a few possible short in solenoid to start with. Disconnect start(small) wire, try to touch battery cable to battery post, had better not arc. Small package on left of starter has me perplexed, low amp relay feeding the starter relay? It should also be dead with key on but not in start position if is a secondary relay.

 

[rslawson]

Red wire comes strait from the battery. The red wire goes to the back side of the small unit on the side with 24V constant. The small wire on the solenoid comes from the back side of the small unit on side. There are 2 wires that also come off that small unit that plug into a pigtail. I assume the small unit is some sort of a relay. I am referring to the small unit that has you perplexed as it has everyone I speak with perplexed!

 

[DMiller]

Most common set up out there for start circuit to take the load off the cab controls. Add a relay between the start switch and the starter, use low amps in the engage circuit to feed the higher amp starter solenoid. Similar to any heavy truck and almost all Ford systems. There should be a hot 24v to the cab controls, that will be from the main starter lug then a 24v down feed to the small relay that once energized feeds a start signal to the starter solenoid, when release the switch the small relay should de-energize and stay that way. I am presuming the tic tic tic you were hearing may have been that small relay and potentially a circuit breaker trying to cut the circuit.

Need to investigate a wiring diagram and validate each wire in the small pigtail as to function.

 

[rslawson]

Removed small screw from solenoid and touched negative post to battery no arcing. Resistance on big post to ground bolt/screw is 200 ohms.

 

[rslawson]

I will trace out each wire on the solenoid including relay and all associated pigtails. I will photograph and label accordingly. I can not locate wiring diagrams anywhere for this machine due to the model number. My local Komatsu dealer can't locate the diagrams either. Nothing for D20S-5.