HM Boxer 427 Temp Control

Frank7847

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Hi there, hoping someone can help. I'm getting little or no temperature from my machine, fluctuates and unreliable, I think my temperature control is faulty. Is there a way of bypassing the electronics completely on the machine so I can have constant hot water? Thanks. Frank
 

wandwizard

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Hi there, hoping someone can help. I'm getting little or no temperature from my machine, fluctuates and unreliable, I think my temperature control is faulty. Is there a way of bypassing the electronics completely on the machine so I can have constant hot water? Thanks. Frank

There are a couple things you can check. I'm supposing your 427 now has an air cooled engine so correct me if I'm wrong on that. However, I think these two things still apply. You may have a bad thermal valve. That won't keep the water from getting hot, but it won't get or stay as hot as it should. The other thing is the high pressure dema solenoid may either be stuck open or not closing all the way. If you check and both those things are working the only other thing I can think of is the actual temp control module. A heavy build-up of scale in the heat exchanges can also be a factor even if all else is working.

I am not as familiar with that machine as the 421, but I"m pretty sure the main things the machine uses to control and maintain the temperature are 1. Thermal relief valve 2. Dema solenoid, and 3. The actuator that controls the diverter valve is vacuum solenoid controlled. Btw, you should make sure the actuator is opening and closing all the way and that no vacuum lines have come loose. Over time the vacuum lines go bad from the heat and just come off or develop cracks. If it's been a while I'd go to the hardware or auto parts store and buy new vacuum hoses if they don't look in good shape.

Lastly, if the problem is with the electronics I'd suggest taking it into https://shop.truckmountforums.com if you can. It may be a simple fix. Although it probably is possible to modify the machine I'd only do that after exhausting everything else. You could do more harm than good. To me, it sounds like your temp control is actually working, but something that module controls is not working like the dema solenoid for example.
 
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Frank7847

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Hi there, hoping someone can help. I'm getting little or no temperature from my machine, fluctuates and unreliable, I think my temperature control is faulty. Is there a way of bypassing the electronics completely on the machine so I can have constant hot water? Thanks. Frank

There are a couple things you can check. I'm supposing your 427 now has an air cooled engine so correct me if I'm wrong on that. However, I think these two things still apply. You may have a bad thermal valve. That won't keep the water from getting hot, but it won't get or stay as hot as it should. The other thing is the high pressure dema solenoid may either be stuck open or not closing all the way. If you check and both those things are working the only other thing I can think of is the actual temp control module. A heavy build-up of scale in the heat exchanges can also be a factor even if all else is working.

I am not as familiar with that machine as the 421, but I"m pretty sure the main things the machine uses to control and maintain the temperature are 1. Thermal relief valve 2. Dema solenoid, and 3. The actuator that controls the diverter valve is vacuum solenoid controlled. Btw, you should make sure the actuator is opening and closing all the way and that no vacuum lines have come loose. Over time the vacuum lines go bad from the heat and just come off or develop cracks. If it's been a while I'd go to the hardware or auto parts store and buy new vacuum hoses if they don't look in good shape.

Lastly, if the problem is with the electronics I'd suggest taking it into https://shop.truckmountforums.com if you can. It may be a simple fix. Although it probably is possible to modify the machine I'd only do that after exhausting everything else. You could do more harm than good. To me, it sounds like your temp control is actually working, but something that module controls is not working like the dema solenoid for example.

Thank you for the speedy reply, really appreciate it. It's an air cooled engine alright, water cooled one gave up the ghost. I'm living in Ireland and unfortunately I don't have any places to bring the machine, no one familiar with them. I'll try the Thermal valve and the high pressure solenoid, just need to find them first. Thank you for the help, wish me luck, this machine has my heart broken. Regards. Frank
 

wandwizard

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Thank you for the speedy reply, really appreciate it. It's an air cooled engine alright, water cooled one gave up the ghost. I'm living in Ireland and unfortunately I don't have any places to bring the machine, no one familiar with them. I'll try the Thermal valve and the high pressure solenoid, just need to find them first. Thank you for the help, wish me luck, this machine has my heart broken. Regards. Frank

Since you have no place to take it I better give you a bit more info. I would suggest first making sure the actuator and vacuum lines are good. If the actuator either isn't closing the diverter valve at all or just not closing it all the way it is either a vacuum line is off or cracked or the actuator is actually bad. They last a very long time but eventually have to be replaced. This is what the machine uses to open and close the diverter valve. It normally should stay closed if the machine has the temp turned up. The temp control will activate it to open it when the machine is getting too hot along with the dema solenoid simultaneously. Basically, it and the solenoid keep the machine from overheating and help control whatever temp you set the dial at.
http://https://shop.truckmountforums.com/ea-valveair-cylinder-maxx-450d470n-560f.html
http://https://shop.truckmountforums.com/solenoid-high-temp.html


Another thing I need to mention is that if either the thermal relief valve or the dema solenoid are bad BOTH will dump a lot of water into your waste tank. You may not notice this if you use an apo. If not using an apo the waste tank will fill up very rapidly. You may do one room and the waste tank is full. That's where all the hot water went. Sometimes the dema soleniod just gets clogged with scale so it doesn't close all the way.The solenoid is a "normally closed" solenoid. In other words it stays closed unless the machine's temp control tells it to open and let some water dump to the waste tank. If the 12 volt coil on that thing goes out I've found they automatically remain OPEN and STAY OPEN! If that happens the machine will dump water CONSTANTLY into the waste tank. You will never get very hot water if that happens!!! Now when the thermal valve goes out they often also stay OPEN and dump a lot of water into the waste tank. However, you will still get hot water, but not near as hot as it should be. Thermal valves are non-electrical valves. They're strictly heat activated. This valve ALSO DUMPS WATER into the waste tank. I suggest getting the machine hot for 10 minutes or so and check to see if any water is being dumped into the waste tank. TURN the TEMP DIAL all the way UP when you do this. The dema solenoid will activate and dump water as soon as you turn that temp dial down below whatever temp is on the thermometer gauge.

If you don't understand any of this or have any questions as you check these things out I'll try to help. I'm not good with the electrical stuff, but might be able to help otherwise. Sometimes btw, just a loose wire is the culprit. Happened to me more than once.

I might add the Hydramaster manual is online and that on most things, if you read the troubleshooting very carefully, it will guide you to the right solution.
 

Frank7847

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This is incredibly helpful, really appreciate you taking the time to respond. I know there is definitely water being dumped back into the waste tank. I’ve also noticed that the overflow on the water box is dumping a lot of water back into the fresh water tank. I’ll have a look in the morning and check the few things, I’ve quite a few Gremlins in this machine, very frustrating when I’ve nowhere to bring it and don’t know how to fix it myself. It was suggested by Hydramaster to put the machine on a pallet and ship it to them in the UK where they’d fix it, I’m between a rock and a hard place...
 

wandwizard

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This is incredibly helpful, really appreciate you taking the time to respond. I know there is definitely water being dumped back into the waste tank. I’ve also noticed that the overflow on the water box is dumping a lot of water back into the fresh water tank. I’ll have a look in the morning and check the few things, I’ve quite a few Gremlins in this machine, very frustrating when I’ve nowhere to bring it and don’t know how to fix it myself. It was suggested by Hydramaster to put the machine on a pallet and ship it to them in the UK where they’d fix it, I’m between a rock and a hard place...

Ok, it sounds like someone rigged up your thermal valve to dump into your fresh water tank. I have been doing the same for years. Based on what you just wrote I'd highly recommend going ahead and descaling the machine. If you don't have a water softener installed they're pretty much a must for heat exchange machines. I would go ahead and order a new thermal relief valve asap. This could very well be your main problem so I'd rule it out before you fool around with anything else. The machine should have either a 165 degree thermal valve or a 180 degree valve. When those go bad generally they remain open as I said above. This prevents the water in the water box from ever getting hot so cold water is going to the heat exchanges. You will probably still get water that is in the 150 to 170 degree F range unless something else is also wrong like the dema solenoid or actuator. You will never get really hot water though if that thing is bad. Those are not too hard for you to replace so I'd get one right away.

Note that some water SHOULD be getting dumped into the waste tank through the dema solenoid, but it SHOULD NOT BE CONSTANT. Remember the temperature control turns this thing on and off. It simply dumps a little hot water and closes right back up.

This is what mine looks like. It is rated for 180 degrees. Pretty sure yours should be the same, but not certain.
ThermalValve180Cropped_op_800x600.jpg
 

wandwizard

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Btw, after reading again what you said about the overflow dumping a lot into the fresh water tank I'm wondering if someone didn't actually REMOVE the thermal relief valve. At any rate that will cost you some temperature at the wand. You may need to post some pics of how this is rigged up, especially the water box. Try to find the thermal relief valve on the machine as well.
 

Frank7847

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Btw, after reading again what you said about the overflow dumping a lot into the fresh water tank I'm wondering if someone didn't actually REMOVE the thermal relief valve. At any rate that will cost you some temperature at the wand. You may need to post some pics of how this is rigged up, especially the water box. Try to find the thermal relief valve on the machine as well.

I went and did my job today but before I started I gave the valves a few light taps with a spanner and I started getting hot water in the water box, not sure if it was coincidence or did the tapping dislodge something. I’ll give it a proper descaling and see how I go. After I turn off my machine my water box overflows, I need to investigate this further too, it’s 1 problem after another but we’ll get there in the end.
 

Swani21

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This is incredibly helpful, really appreciate you taking the time to respond. I know there is definitely water being dumped back into the waste tank. I’ve also noticed that the overflow on the water box is dumping a lot of water back into the fresh water tank. I’ll have a look in the morning and check the few things, I’ve quite a few Gremlins in this machine, very frustrating when I’ve nowhere to bring it and don’t know how to fix it myself. It was suggested by Hydramaster to put the machine on a pallet and ship it to them in the UK where they’d fix it, I’m between a rock and a hard place...

Ok, it sounds like someone rigged up your thermal valve to dump into your fresh water tank. I have been doing the same for years. Based on what you just wrote I'd highly recommend going ahead and descaling the machine. If you don't have a water softener installed they're pretty much a must for heat exchange machines. I would go ahead and order a new thermal relief valve asap. This could very well be your main problem so I'd rule it out before you fool around with anything else. The machine should have either a 165 degree thermal valve or a 180 degree valve. When those go bad generally they remain open as I said above. This prevents the water in the water box from ever getting hot so cold water is going to the heat exchanges. You will probably still get water that is in the 150 to 170 degree F range unless something else is also wrong like the dema solenoid or actuator. You will never get really hot water though if that thing is bad. Those are not too hard for you to replace so I'd get one right away.

Note that some water SHOULD be getting dumped into the waste tank through the dema solenoid, but it SHOULD NOT BE CONSTANT. Remember the temperature control turns this thing on and off. It simply dumps a little hot water and closes right back up.

This is what mine looks like. It is rated for 180 degrees. Pretty sure yours should be the same, but not certain. View attachment 77594
I don't believe the 427 runs a dema valve. Well at least I've never found it on my machine or in my diagrams. It does run 2 temp sensors that can also throw off your heat if they become loose or scaled up.
 

wandwizard

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I don't believe the 427 runs a dema valve. Well at least I've never found it on my machine or in my diagrams. It does run 2 temp sensors that can also throw off your heat if they become loose or scaled up.
I found what looks like 3 places in the 427 manual that shows what they refer to as a "dump solenoid". Page 1-69 shows it as # 25 in the diagram. The next page shows it as part #000-169-120. I found it again on page 5-5 listed there as a Low psi dump solenoid. Pretty sure they're one and the same, but that this is a different solenoid than is used on my Boxxer 421. Sometimes, just taking them apart and cleaning them out restores function unless the 12 Volt coil has gone out.

This solenoid should be near or mounted to the waste tank. You should very carefully read pages 5-8,9 in the manual under the heading, "Unable to achieve normal cleaning temperature". I suspect that when the original engine was removed the machine was modified in some way and could be causing some problems. You may need expert help with this unless you just get lucky. Perhaps @Todd the Cleaner or someone else might have some more insight into the problem.

https://hydramaster.com/Manuals/man182-068.pdf
 

Frank7847

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I was back at it again today, weather has been terrible over here and I haven’t any place to get good cover from the elements. When the water box is full and I turn off the fresh water pump, the water gets very hot which is great however as soon as I turn back on the water pump it just keeps on pumping and the water box gets cold and water is constantly pouring out of the water box. Do this point to Thermal relief valve? I was looking through the manual but can’t seem to spot where it is on the machine. I think I’ll order one and see if it will solve the problem.
 

Swani21

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I was back at it again today, weather has been terrible over here and I haven’t any place to get good cover from the elements. When the water box is full and I turn off the fresh water pump, the water gets very hot which is great however as soon as I turn back on the water pump it just keeps on pumping and the water box gets cold and water is constantly pouring out of the water box. Do this point to Thermal relief valve? I was looking through the manual but can’t seem to spot where it is on the machine. I think I’ll order one and see if it will solve the problem.
If your water box is over flowing that can cause significant heat loss. You probably need a new float kit. Also I'll try and upload my pics of my hi temp solenoid to show you. The hi temp solenoid can be taken apart and cleaned. Did you find the lights in your fuse box for heat mode and divert mode?
 

wandwizard

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I was back at it again today, weather has been terrible over here and I haven’t any place to get good cover from the elements. When the water box is full and I turn off the fresh water pump, the water gets very hot which is great however as soon as I turn back on the water pump it just keeps on pumping and the water box gets cold and water is constantly pouring out of the water box. Do this point to Thermal relief valve? I was looking through the manual but can’t seem to spot where it is on the machine. I think I’ll order one and see if it will solve the problem.

I hate to say it, but from what I can tell from the manual there doesn't appear to be a thermal valve. I don't know how the machine originally worked so maybe @Swani21 can confirm this. The thermal valve normally helps keep the water in the water box pretty hot before it goes to the heat exchanges. I can well imagine if they didn't put one in there it would cause some problems. Btw, the thermal valve will have about a 3/8'th inch hose going to it. Normally it's routed to the waste tank and dumps water in there although some route it to the fresh water tank like I do.

If the water box overflows that is normally either the float in there is either bad or could simply be cocked sideways a bit so it doesn't shut off right. Make certain it's straight up and down. If it's an old float you may need to replace it.
 

Frank7847

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I was back at it again today, weather has been terrible over here and I haven’t any place to get good cover from the elements. When the water box is full and I turn off the fresh water pump, the water gets very hot which is great however as soon as I turn back on the water pump it just keeps on pumping and the water box gets cold and water is constantly pouring out of the water box. Do this point to Thermal relief valve? I was looking through the manual but can’t seem to spot where it is on the machine. I think I’ll order one and see if it will solve the problem.
If your water box is over flowing that can cause significant heat loss. You probably need a new float kit. Also I'll try and upload my pics of my hi temp solenoid to show you. The hi temp solenoid can be taken apart and cleaned. Did you find the lights in your fuse box for heat mode and divert mode?

I had a look at the fuse box and the divert mode is lighting up alright.
 

Swani21

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Frank when you flip the switch for heat mode does the diverter cylinder extend and push the diverter arm over? This causes the exhaust to be routed through the heat exchanger to heat the water. In this picture you can see the diverter cylinder is retracted and in non-heat mode. This is located on the exhaust side of the machine towards the rear.
truckmount diverter unedited.jpg
 
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sunrisecarpet951

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The 427 does has the valve on the back of the waste tank but I’m about 99 percent sure it doesn’t have a temp valve but the 421 does have them. It does us RTD sensors for heat but those tend to only effect the pump when not properly working. I would check the temp sensor that goes to the gauge and like stated above I would make sure the diverter valve is opening properly and that the dema valve is not staying open and dumping into the waste tank prematurely. I would always check the air actuator that controls the diverter they will go back if your water box ever overflows and the suck in water and check the vacuum solenoids that control the air flow to the actuator as well they get weak over time when the little filters plug up and they won’t have enough suction to activate your heat
 
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