El Diablo Flow Swich, run away heater

RoboShark

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hi guys I'm new with el diablo,just bought it used with 1560 hrs,Honda 24 hp engine,and I'm really scared of what this thing is doing,my pressure goes up really fast as soon as I turn the heater on,I think my heater it's firing with out using my wand any idea how to fix it :(
Either the flow switch is malfunctioning or the thermostat is. When you pull the wand trigger it should be instantaneous on and off. If its takes too long to go on or too long too go off then get a new switch.

Has it been doing this from the start? They could have bypassed the switch to run off the thermostat. That is a bad idea but can be done for a job or two til the new part arrives.
 

extremecarpet

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Thank you Raboshark,Yes I had the machine for a week and that's how it was and I've been working like that,really messed up I turn the heather on and have to run inside the house to press the wand trigger before pressure goes up,anyways I will check the flow switch,but where the heck is that flow switch,send me a pic of it if you can, thank you
 

Ara Klujian

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Without a doubt you should be able to hear if that heater is firing or not. You really need to be sure if it is firing before you presume anything. What I will do is walk you through some simple proceedures to make sure if it is firing on its own or not. With the engine off and the key in the on possition there should be absolutely no sounds coming from the truckmount. Flip the switch for the heater to the ON possition briefly. The only thing you be hearing is the squierl cage fan. If your heater is firing at this point you will hear a bass tone. Similar to a sub-woofer. The bass tone is always more prominent when it first turns on and when it shuts down. Confirm at this point if your heater is or is not firing. Another way to confirm would be to see or feel exhaust or hot air flowing out the exhaust port. If you confirm your heater is running under these circumstances, you need to turn the truckmount and the heater switch completely off and locate and inspect the flow switch for any debris. Sometimes debris and fiber can get caught on the spring inside the flow switch. Or scale buildup can prevent the bullet from moving freely inside the flow switch bore.
If the problem only happens when the water pump is running, try descaling your truckmount after you confirm the spring is clean. If descaling your truckmount does not correct the issue then you may need a new flow-switch. A worn flow switch with hundreds of hours on them can become pitted inside the bullet bore. This prevents the flow switch from operating correctly.

It is very important to familiarize yourself with the way your truckmount sounds when the heater is on. The pitch may change from day to day depending on the barometric pressure but you should always know if it is on or not. Heat run-on is a very serious issue and needs to be addressed. Your safety and the safety of others depends on it. The most important part is knowing if this is really happening or not. To say you think heat run-on is occuring needs to be confirmed. If you are still unsure whether or not it is working properly, I strongly suggest you take it in to a reputable service center for repair.
 
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Ara Klujian

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yhst-6302467517443_2255_8271229
 

RoboShark

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Are you running the El D or the Powermatic like me? This issue should be diagnosed the same on both right. I've never worked with the El D but I know it's basically the same as the Powermatic.

I think he should fire up the machine then turn the heater on with the warm up engaged. Then the heater should be firing and you can turn the thermostat left and right to turn it off and on. If it doesn't turn it off and on then the thermostat might be causing the runaway.
 

Ara Klujian

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The engine does not need to be running for heat run-on to occur. Both methods of testing should be employed but if heat run on is happening, then there is no need to run the engine. Unless you believe descaling will rectify the issue and that of course would be done without heat or closely monitoring the system temp while descaling. The heaters electrical system is completely independent from everything else. I just thought it would be easier for him to identify the sound it makes without all the added noise of the blower and the engine.
Yes they are relatively the same in relation to heater wiring schematics and certain heater parts.
 

Ara Klujian

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yes! Then descale after. looking inside the bore will give you an idea of how much scale is in the system too. If the scale is apparent you will see a white chalky residue on the bullet and inside the bore. With the machine off unscrew the hex cap to the cylinder. If you have to pull probe out, do so. If your not careful you can damage the probe when you take off the hex cap. Place a rag over the opening. back off the pressure regulator all the way. Then kick on your pump for about 1 second and turn the pump off immediately. You should be able to catch the bullet and the spring with your rag. I usually just use my hand but its safer and less of a mess with a rag. This will allow you to clean the spring.
 
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Ara Klujian

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yes! Then descale after. looking inside the bore will give you an idea of how much scale is in the system too. If the scale is apparent you will see a white chalky residue on the bullet and inside the bore. With the machine off unscrew the hex cap to the cylinder. If you have to pull probe out, do so. If your not careful you can damage the probe when you take off the hex cap. Place a rag over the opening. back off the pressure regulator all the way. Then kick on your pump for about 1 second and turn the pump off immediately. You should be able to catch the bullet and the spring with your rag. I usually just use my hand but its safer and less of a mess with a rag. This will allow you to clean the spring.

 

extremecarpet

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yes! Then descale after. looking inside the bore will give you an idea of how much scale is in the system too. If the scale is apparent you will see a white chalky residue on the bullet and inside the bore. With the machine off unscrew the hex cap to the cylinder. If you have to pull probe out, do so. If your not careful you can damage the probe when you take off the hex cap. Place a rag over the opening. back off the pressure regulator all the way. Then kick on your pump for about 1 second and turn the pump off immediately. You should be able to catch the bullet and the spring with your rag. I usually just use my hand but its safer and less of a mess with a rag. This will allow you to clean the spring.
Sound great
 

Ara Klujian

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ok , thats good information. That tells me that your thermostat and fuel solenoid is working properly. Two things could be wrong here. Either you have a wand with continuous bypass or the flow switch bullet is getting stuck. Like I mentioned above, the flow switch could have little pits in it or is distorted somehow preventing it from returning back down to its bottom possition. Or the flow switch is mounted horizontally.
The flow switch needs to have a smooth bore so the bullet can move up and down freely. Try installing a new flow switch and see what happens. Its always a good idea to have a spare flow switch on hand anyway. Keep us posted. Threads like this help other people too.