Alternator and fan issue on our 900

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kubota orange

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We had to do a engine swap on our 2003 Kubota RTV 900 because one of our employee's blew the engine up by running it with no oil :bonk:

Anyway, brand new motor installed, everything is working good except the alternator and electric fan aren't working right. I traced the wiring back to the same switch/relay on the back of the cab and it seems the alt and fan share this relay. I checked the fuses and replaced a blown fuse that controlled the alt, and ran it again for about ten minutes, then another blown fuse. THought maybe a wire was shorting, unpeeled all the wiring harness and found no frayed or suspicious wires. One thing I need to question though, should the wire that leads to the sensor that goes into the waterpump and thermostat housing have 12v power? I was always under the assumption those sensors operated by grounding the circuit when it got to a certain temp? Because mine has 12v, which is strane to me.
 
RTV Schematic

Hope this helps......God bless.........Dennis
 

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Thats what I was just looking at, my pink wire going to the temp switch on the waterpump flange/head has got 12v going to it when the key is on and motor running?
 
And it should have 12v all the time. The temp switch on the motor is the ground for the relay. When the engine gets too hot, it switches on, turns on the relay and 12v get sent to the fan. If you unhook the pink and touch it to a good ground, the fan should come on.
Follow the post and test each point and one of them should lead you to your problem.
 
Perhaps this will help.

1= RG red/green to relay should have power all the time with key on. 12v reading here. This is the power into the relay to activate it's switch when the temperature sender reads engine temps that are too high and grounds out. So low voltage or not voltage and the relay will not work. Possibly bad fuse or bad wire feeding the relay.

2= RL red/blue to relay should have power all the time with key on. 12 v reading here. This power gets sent to the fan when the relay is activated, like when the pink wire is grounded. Low or no voltage here is bad fuse or bad wire.

3= P pink to coolant temp switch should be equal to a ground, so touch it to anything grounded and the fan should come on or at least show power to the RB red/black wire going to the fan, when key is on. If fan comes on and it doesn't when engine is too hot, bad temp sender.

4= RB red/black is power to fan when temperature sender reads high or pink is grounded. Low or no voltage here and relay is bad.

5= B black from fan is ground so touch it to ground if unsure it is grounding and with key on, pink grounded, fan should come on.

If you have 12v on RB (red/black) when P (pink) is touched to ground and no fan, fan is bad. Or remove fan and touch wires directly to battery to see if it still doesn't work just to be sure.

You need to be able to read voltage not just if a test light comes on. So a voltage gauge is necessary to test this properly. Relays require 12v to work properly and fans do as well. Check battery voltage while you are at it.

Good luck.
 
All of that checks out good. I can turn the key on and ground the pink wire and the fan comes on and you can hear the relay click while you do that, so I'm assuming the relay is okay. I even tried a spare thermoswitch/sensor I had and swapped that out on the motor. Nothing. I'm at a loss. So now I've just rigged the fan to come on when the key is on by running the pink wire to battery ground.
 
I had a problem one time with a wire on the back of the cab. It was coming from the relay for the eng. stop solenoid. Once cranked I could not kill the engine by key, had to do so manually. Any how what I had found was a wire had corroded and broke inside the insulation. I couldn't physically see it. I noticed a small amount of corrosion on the wire. tried to wipe it off and realized the wire felt funny (felt strange when bent back and forth). I agree with Spud Hauler, I believe it's in the wiring. Some of those wires are bent in such a way that they could break over time from the stress. Hope this helps you.
 
If the fan checks out then what exactly is the problem with the fan? They register pretty high on the heat gauge before the fan comes on normally. So if you're waiting for the fan to come on it may take some time and hard work to get the new engine to get to an overheat condition.

You mentioned blown fuses. Maybe you have other issues like a short that is the real problem at this point.
 
I agree with Spudhauler .It sounds like a short to me because of the fuse blowing. Maybe a wire was nicked when swapping out the engine. Is the fuse the right size? bordercollie
 
The fan doesn't come on, even when the needle on the gauge is almost in the red. I unwrapped the wiring harness and searched for a shorted out wire and could find nothing. Right now we need the machine up and running so I rigged it to get it out there without overheating.
 
I had a 900 and remember the needle being real high lots of times. They run hot. Or do you have a cooling issue as well. Like plugged rad fins or a air pocket in your coolant?
Plus the electrical issue. No fun is it!
 
Looking at the wire diagram that RG (red/green) feeds the fan relay, brake switch and alternator regulator.

You can unplug the brake light switch to test it. And leave it unplugged until the problem is solved.

I would suspect the regulator might be bad.

When running and engine reved up you should see approximately 13-14 volts at the battery posts on your meter. If lower, it's not charging high enough, if higher, it's too high and will fry the battery eventually.
 
with the alternator fuse blowing, I'd also be looking at the actual connections on the alternator. Remove them, clean them, and put some di-electric grease on them to be sure. Then read your voltage output at the alternator as was suggested. Sounds like the relay, temp switch and fan are good, just the alternator fuse keeps blowing. That also might mean your battery will go dead over time, as the alternator wont be charging it with a blown fuse. Been there done that.
 
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