komatsu pc50 heat not working

I have recently picked up a pc50.

The heat is not working at all, it just blows cold air.

I blew out the heater core and filters so its getting good air flow. It seems there is no coolant circulating as the hoses going to the heater core are cold.

The fan itself sounds and rough shape. I'm not sure of the temp control dial is working or if controls anything.

Any suggestions??

Thanks

Check for shut off valves on the engine block and make sure they are open. If so then you will have to find the unit in the cab and make sure the control cables or solenoids are working.

I did check the shut off valve, it was open (looked like a gate valve, screwed out)

When you said "find the unit", did you mean the temp control unit? That is what I was guessing as well, but I have no idea how it works. The older ones just had a manual flap/door that would pull the hot/cold air. This seems to be an electronic dial, but what does the dial control? Any ideas are greatly appreciated.

John C. said:

Check for shut off valves on the engine block and make sure they are open. If so then you will have to find the unit in the cab and make sure the control cables or solenoids are working.

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You're on the right track with the cold coolant lines. Look for a second valve. Should be one on both the supply and return.

Ditto, if you have verified that the shutoff valve, or two valves, in the heater hose connections to the engine are open, but still have cold hoses, then you likely have a clogged heater core. I've had to flush out the core on excavators a number of times, it's a common problem. You need to disconnect the heater hoses at the engine then flush back through both hoses with water pressure, sometimes it requires using a little air pressure as well to get the water moving through the core to dislodge the gunk. Even then you may not succeed in cleaning the core entirely, but enough to produce some heat, a severely clogged core would require replacement.

Getting to the core to replace is another challenge. One would need to know the exact model and serial number for more specific advice, but with pretty much any excavator cab, it seems they install a heat/air unit, then build everything in the cab around it, you typically pretty much have to blow up the inside of the cab to service the unit.

All the Japanese excavators I've worked on had two valves on the engine. The heater AC unit is in the cab next to your right leg and behind the pilot control console. Hopefully yours has regulated air doors and not a shut off for the hot water valve. Most of the Japanese units use the air mixing doors and the solenoids burn up because of dust gets stuck in them and then gets frozen in place.

You can obtain a book with a search on the internet. As willie59 says, blow water or air through the hoses from the engine side to see if you have flow. If you can't get water to go through you will have to pull the unit complete to be able to work on it. You can try blowing pressurized air back through the ducting but I haven't had much luck with that.

I checked the microfisce as well as the machine and there seems to be only 1 shutoff manual valve (on the heat supply side). attached is the microfisce as well..

I'm gonna pull the engine side hoses tomorrow and see if I can push some water through the core. I ran it for 1hr this morning and the hoses were ice cold. If I'm getting flow, I'll have to sadly rip apart the cabin to see if the damper is stuck or heater core still clogged with dirt.

thanks for the advice guys. the machine is past due on 500 hr maintenance, so, i'm slowly working through the machine bringing it back to shape. i think it needs a pin/bushing on the bucket. I also need to finish some site work before the heavy snow sets in here in boston area.

John C. said:

All the Japanese excavators I've worked on had two valves on the engine. The heater AC unit is in the cab next to your right leg and behind the pilot control console. Hopefully yours has regulated air doors and not a shut off for the hot water valve. Most of the Japanese units use the air mixing doors and the solenoids burn up because of dust gets stuck in them and then gets frozen in place.

You can obtain a book with a search on the internet. As willie59 says, blow water or air through the hoses from the engine side to see if you have flow. If you can't get water to go through you will have to pull the unit complete to be able to work on it. You can try blowing pressurized air back through the ducting but I haven't had much luck with that.

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sadegs said:

I'm gonna pull the engine side hoses tomorrow and see if I can push some water through the core. I ran it for 1hr this morning and the hoses were ice cold. If I'm getting flow, I'll have to sadly rip apart the cabin to see if the damper is stuck or heater core still clogged with dirt.

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If both hoses are cold, there's NO flow right now. If you can flush/blow it out and get some flow then it will probably work. I'd try to find a valve at the heater, because I'd think that even a plugged core would let enough water through that one hose would be warm.

Of course I don't know how much harder it is to get at the heater than the hoses at the engine, and I don't know how bad the coolant/insides looks either.

unhook the hose from the "gate valve" and see if you have flow there. I have ran into this more than once where the valve unscrewed from the gate that was stuck in the closed position.

bill onthehill said:

I have ran into this more than once where the valve unscrewed from the gate that was stuck in the closed position.

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Anything's possible.

willie59 said:

Anything's possible.

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gate valves do that all the time, or rather bubba honkin on them does that all the time. Willie just has too much finesse. How somebody would have put a gate valve on a heater line?- "anything's possible"

Delmer said:

gate valves do that all the time, or rather bubba honkin on them does that all the time. Willie just has too much finesse. How somebody would have put a gate valve on a heater line?- "anything's possible"

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Hey, I took the swing gearbox apart on a Cat 320C LC once and found a live .22 Cal round inside it. Yep, anything's possible.

-- an update --

I managed to get ahold of the company and tech that was performing service on the machine before I acquired it. Super cool dude that was very helpful. Turns out, I was wrong, there was a second water valve - it is inside the heater box, AND, Komatsu has a service bulletin on it!! The condensate from the AC drips into the motor actuator and water valve causing it to fail. There is a service kit that will correct the issue.

So, I guess good news is that I now know what the problem is. Bad news is that I have to remove the heater/ac box (remove cab, gas tank, etc..) to correct the issue.

Apparently it is an issue with PC27 - PC50 models. I've attached a PDF of the service bulletin in case there is anyone else that runs into the same issue.

I feel your pain.

It looks like you could just about get at that valve from the inside to cut the control rod loose and operate it manually, if you don't mind a hack job.

Also, is a "minus screwdriver" a flat screwdriver? that one was almost as hard as the Rudolph the red nosed reindeer cartoon.

I was thinking the same thing, to see if I can hack inside the cab, at least for the winter. My other hack idea was to run 2 new coolant hoses from the engine side to an old car heater core inside the cab just to get some heat for the winter.

"minus screwdriver" - ha, i got a laugh out of that one as well.

Delmer said:

I feel your pain.

It looks like you could just about get at that valve from the inside to cut the control rod loose and operate it manually, if you don't mind a hack job.

Also, is a "minus screwdriver" a flat screwdriver? that one was almost as hard as the Rudolph the red nosed reindeer cartoon.

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