Bypass faulty hilimit swtich
- Thread starter Kiloman
- Start date
Before I tell you this I must warn you that you are going around a safety device that is on your burner for a reason. You could cause serious injury to yourself and others that could be around the burner.
Next, do you have a thermostat atleast? I only ask because some burners work on high limits to control heat while others work on thermostats with a high limits as a back up. If you just have the high limit don't use the burner before you replace the switch, if you have a thermostat well here you go, but still replace that high limit asap.
Two wires go to the high limit switch, trace them back 6 inches to a foot and cut (Power is off I am assuming). Take the two wires that run back to the burner unit and twist them together. I would insulate the wires as well, ie wrap electrical tape at the very least around the twisted wires. The high limit switch works either on or off, and on lower temps then the high limit a 12v circuit is just completed. When the high limit is reached it breaks the circuit which blocks fuel from being allowed to the nozzle.
Burners are pretty simple, high limit, thermostats, and flow switches are just completed circuits and typically run one to the next.
Next, do you have a thermostat atleast? I only ask because some burners work on high limits to control heat while others work on thermostats with a high limits as a back up. If you just have the high limit don't use the burner before you replace the switch, if you have a thermostat well here you go, but still replace that high limit asap.
Two wires go to the high limit switch, trace them back 6 inches to a foot and cut (Power is off I am assuming). Take the two wires that run back to the burner unit and twist them together. I would insulate the wires as well, ie wrap electrical tape at the very least around the twisted wires. The high limit switch works either on or off, and on lower temps then the high limit a 12v circuit is just completed. When the high limit is reached it breaks the circuit which blocks fuel from being allowed to the nozzle.
Burners are pretty simple, high limit, thermostats, and flow switches are just completed circuits and typically run one to the next.
Russ Johnson
Equipment Expert
I wouldn't go cutting any wires. What if it's not the hi limit? Then you've got patched-together wiring. If your switch has the slide on terminals on it, pull the wires loose and use a short piece of wire to tuck into the terminals to jump them. If the cord is molded in, follow it back to the control box, figure out where it attaches, and disconnect it. Tie the spots together where the cord came off, and it's bypassed without damage.
I guess I gave you the in the field and no time to waste following wires version. If you have time to spare follow Russ, I always have a wide assortment of butt connectors, wire strippers, and crimpers always in the truck. So if I cut and test and find I was wrong, its only 2 minutes to repair if needed.
All my stuff breaks in the field and when you are getting paid by the hour you need to find and implement a solution as quickly as possible. If the solution gets the job done and me back to the shop well then I can figure out how to make it reliable.
All my stuff breaks in the field and when you are getting paid by the hour you need to find and implement a solution as quickly as possible. If the solution gets the job done and me back to the shop well then I can figure out how to make it reliable.
Sirocco Jerry
Active member
the MOST important thing is..
NEVER "guess" at what you are doing..
PROVE that what you are doing is correct, and reasonable.
Respect the Tech !
Good job Russ and Benjamin :{)
NEVER "guess" at what you are doing..
PROVE that what you are doing is correct, and reasonable.
Respect the Tech !
Good job Russ and Benjamin :{)
Kiloman
New member
Thanks Jerry it was a 2 month old themostate what junk they sell these days.When winter comes there will be A bullet proof themostate with a themocoupler and digital board,and readout installed.Able to set within a 5 degrees deadband.This is sad day when products dont last.Then again it was only 27.00 bucks but still.
Russ Johnson
Equipment Expert
Most manufacturers have a 90 day warranty on parts. Might want to check.
Russ Johnson
Equipment Expert
Is the whole burner starting and stopping, or are you just controlling a solenoid with the thermostst?
Russ Johnson
Equipment Expert
No, what I'm asking is: Does the flow / pressure switch /thermostat shut the whole burner down (Alkota 12 volt), or does it operate the fuel pump solenoid (Hydro Tek 120 volt)?
Russ Johnson
Equipment Expert
Hal, do you have a wiring diagram that you could scan and send me? I'm wondering if the thermostat is exposed to excessive amperage.
Its the Largo built or the one espec sells.
I have the 120v version and am on my third thermostat I think.
Kiloman have you tried the adjustment screw on the back, and looked to see if the thermostat switch was actually working? I found on my second one the adjustment screw just needed a little turn and was able to keep the second thermostat going for another 8 months before I got sick of it and just replaced it.
The thermostat is $30 online and $90 at my local vendor, so I keep one spare that I ordered online as my backup. I either buy 3 and have 2 spares or buy 1 local and have no spares. Plus spare thermostats, unloaders, and flow switches are always good to have just in case.
I have the 120v version and am on my third thermostat I think.
Kiloman have you tried the adjustment screw on the back, and looked to see if the thermostat switch was actually working? I found on my second one the adjustment screw just needed a little turn and was able to keep the second thermostat going for another 8 months before I got sick of it and just replaced it.
The thermostat is $30 online and $90 at my local vendor, so I keep one spare that I ordered online as my backup. I either buy 3 and have 2 spares or buy 1 local and have no spares. Plus spare thermostats, unloaders, and flow switches are always good to have just in case.