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Walker Diesel overheating, fan not switching to 2nd stage

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marne

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Discussion starter · #1 ·
Hi again everyone,

after the winterbreak my 2009 MDDGHS doesn't work as it should.
The radiator fan works continous, nicely and changes blowing direction as it should. But after about 0.5-1hour the mower starts overheating and goes up to 210°F.
I never really cared but I think there was a second blower stage with higher revs when it's hot and this seems to be missing right now.

The radiator for sure is clean between the fins and I cleaned all the connectors obviously belonging to the cooling system. I tensioned the belt for the pump, checked the fluid level and thinks there is flow in the rad.
My online research lead me to two possible plroblem sources: the fan control box or if I remember correctly, theres is a thermostate especially for the second blower stage, hopefully this went out.
Anybody could point me please to correct direction how to spot the problem source?
As I'm from the other side of the pond, walker dealers are literally non existing so no parts source to quickly try and check.
I think it's an electical issue, best would be the thermostate which can be bridged with a switch or replaced, but how can I check?

Many thanks in advance
Marne
 
#2 ·
Make sure the unit is at 205 deg or higher. Ensure the black ground wire from temp switch has good connectivity to the mower frame. Check for continuity between the green wire and the black wire on the temp switch at the radiator. If you have no continuity, the temp sw is no good. If you have continuity, check for continuity between the green wire at the temp sw and terminal 85 on relay D, fan speed control relay. If there is continuity, replace the relay. If there is no continuity, check the wire and terminals.
 
Discussion starter · #4 ·
So today I went out with the MD. I bridged the temp switch with an manual switch. Using it, allowed me to spin the fan at higher revs. Great I thought.
So far so good, it seemed to work, when the temp gauge climbed above 210°, I switched on the ground and the fan cooled down the engine a little better. After 1.5 hours the temps went suddenly up to 220°, I lifted the hopper and saw a fan standing still, trying a little jittery to spin.

Stopped the engine and waited 2-5 minutes. Ignition on again and the fan started to spin faster than it did before with my manual ground switch, which was set to "off" at this moment. It let me mow far a while, then again, standing still:(.

So it seems as it's definitely not the temp sw.
the battery is nearly dead, I replace it tomorrow maybe it helps, but the voltmeter displays 13-14V all the time when the engine runs so I think this is not the source of the problem.

I was checking the wiring diagramm for terminal 85 on relay-d, which I guess is the fan control box, mine is a sealed unit with a different colour scheme with no yellow wires. Or is relay-d the the circuit breaker? Mine have only red wiring on them.
Any further help is highly appreciated, I really don't want to toast the kubota... how much I love air cooled engines.
 
#5 ·
Get your battery load tested. Then check the charging output of the alternator at the battery terminals. The “D” relay is a small cube relay just like the start relay. The “D” relay should be located near the sealed fan control unit. It is a separate piece and not part of the control unit. Looking at the wiring diagram I have for the MDD, Relay “D” should have a yellow, green, grey and two black wires. The other issue is the fan itself. It could be heating up and causing running issues, like it being jittery as you posted. The older units had fans mounted inside the radiator causing premature wear on the fan motor. The newer units have the fan on the outside of the radiator I believe.
 
Discussion starter · #6 ·
Many thanks Walker56 for taking your time with me.
I replace the battery completely, the old one is definitely done and I gonna search for relay-d again, hopefully I can figure it out. I'll report the results. So far many, many thanks again!!!!
 
#7 ·
You can jump the green wire At the temp switch to ground and allow the fan to run full speed all the time. It is no big deal and will have no effect on the fan. You still need to verify if the relay is good. I have a feeling that your fan is on its way out. You can easily check it. The next time the fan is jittery, move it by hand utilizing a piece of thin wood or plastic to get to the blades. If it takes off running, your fan is ng or you can test for voltage at the fan connector. If you have voltage at the connector, the fan is ng
 
Discussion starter · #8 ·
Once again many thanks Walker56, I gonna check this tomorrow, if the fan is done they'll charge an arm and a leg from me, imagine, this walker is 38.000 USD here and they charge over 60$ for a walker spray can, don't want to know what they want for the fano_O. crazy
 
#9 ·
marne said:
Once again many thanks Walker56, I gonna check this tomorrow, if the fan is done they'll charge an arm and a leg from me, imagine, this walker is 38.000 USD here and they charge over 60$ for a walker spray can, don't want to know what they want for the fano_O. crazy
Click to expand...
I just checked. The MDD still has the fan inside the radiator. The liquid cooled gas Kohler engines had the fan moved from inside to outside the radiator. I guess due to the diesels configuration within the frame, that is the best place for the radiator fan. Here is a link to the replacement fan
https://www.walkerpartsdepot.com/item/7429-6/
 
#11 ·
My fan control went out a few years ago. Wired fan direct to battery with toggle switch. Runs full speed only. Kinda got used to it this way as I can cool the engine after shutting down, so long as I remember to turn it off later.
Any automotive fan that will fit should work. There is a fair bit of room on that side of the engine.
 
#12 · (Edited)
windflower said:
My fan control went out a few years ago. Wired fan direct to battery with toggle switch. Runs full speed only. Kinda got used to it this way as I can cool the engine after shutting down, so long as I remember to turn it off later.
Any automotive fan that will fit should work. There is a fair bit of room on that side of the engine.
Click to expand...
@windflower , do you find a buildup of grass on the radiator since your setup only rotates in one direction?
 
#16 ·
windflower said:
Having to do it manually also keeps me from falling asleep on those hot days.
Local dealer didn't have one in stock and I just got used to it the way it is. Just replaced the momentary switch for implements with a toggle. If I was inspired it would be easy to reverse the polarity.
Click to expand...
Yes, it would be easy. For me though, I think it would be too easy to forget the fan was in the wrong rotation, lol.
 
Discussion starter · #17 ·
Walker56 said:
Are you in Australia?
Click to expand...
Not Australia, it's Europe where walker rips you off that bad, even with shipping and customs, parts are often 1/3 cheaper when I order from the US.

So this is what happened yesterday:
I replaced the battery and when I tried to start, I noticed it was dead from the beginning, using a voltmeter would have saved me from this, but who expects this from a brand new unit?
As I had to mow, I put back the old one and searched for "relay d", thanks to walker56, I found it and to my surprise the connectors where really dirty and greasy, obviously someone sprayed it in the past and gobs dirt built up in there.
Cleaned it, jump started the mower and went mowing. Sadly I only had one lawn with 5k ft² which was dense enough to rise the temps. The 2nd stage did not kick in (as it did once before a few days), but I was able to force the 2nd stage with the manual jump-switch. This time the fan didn't stop and cooled the engine perfectly. But the weather was colder and I had no large, dense lawn left to mow. So I'm not sure if cleaning "relay d" already solved the issue with the jittery fan or if it was just not hot enough. So no proof results.

Anyway I noticed that when lifting the power hungry high dump, the fan in 2nd stage definitely slowed down more than a bit, nearly down to stage 1 (by hearing). So the battery could be a problem source as well. The end of next week, I got 7k ft² to mow, which are 2ft high, there I can stress the system enough I hope, to get further insights and get the new battery till then.

Definitely keep you updated, as I hope threads like this help others as well.
Windflower, directly connecting the fan could be an acceptable last resort for me, as the fan or it's control box will be around 500$ here, which is just not funny anymore.

So far many, many thanks again to all so far and I'll report.
Marne
 
#18 · (Edited)
marne said:
Not Australia, it's Europe where walker rips you off that bad, even with shipping and customs, parts are often 1/3 cheaper when I order from the US.

So this is what happened yesterday:
I replaced the battery and when I tried to start, I noticed it was dead from the beginning, using a voltmeter would have saved me from this, but who expects this from a brand new unit?
As I had to mow, I put back the old one and searched for "relay d", thanks to walker56, I found it and to my surprise the connectors where really dirty and greasy, obviously someone sprayed it in the past and gobs dirt built up in there.
Cleaned it, jump started the mower and went mowing. Sadly I only had one lawn with 5k ft² which was dense enough to rise the temps. The 2nd stage did not kick in (as it did once before a few days), but I was able to force the 2nd stage with the manual jump-switch. This time the fan didn't stop and cooled the engine perfectly. But the weather was colder and I had no large, dense lawn left to mow. So I'm not sure if cleaning "relay d" already solved the issue with the jittery fan or if it was just not hot enough. So no proof results.

Anyway I noticed that when lifting the power hungry high dump, the fan in 2nd stage definitely slowed down more than a bit, nearly down to stage 1 (by hearing). So the battery could be a problem source as well. The end of next week, I got 7k ft² to mow, which are 2ft high, there I can stress the system enough I hope, to get further insights and get the new battery till then.

Definitely keep you updated, as I hope threads like this help others as well.
Windflower, directly connecting the fan could be an acceptable last resort for me, as the fan or it's control box will be around 500$ here, which is just not funny anymore.

So far many, many thanks again to all so far and I'll report.
Marne
Click to expand...
I would start with a fully charged battery and do a charging system check. If the high dump is causing the fan to slow down, your alternator may not be putting out enough amps to support both functions. Have you checked your alternator belt to ensure it is tight and not slipping? Your fan control is working. You can jump the green wire to ground and it will run the fan at full speed all the time and it will still reverse to blow the debris out, which is important.
 
#20 ·
The reason the fan has two speeds is probably because the alternator can not support the fan running constantly. I use to have cars with engine driven fans off the belt/waterpump. Removing these gains some HP but you need to go to electric fans. Electric fans would run the battery down on these cars in city driving taxing the alternators and burning up wiring and alternators.
 
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