Heater problem

twmackey

Well-known member
Jun 25, 2012
53
#1
I have a Teledyne Laars EPM 175,000 BTU heater and it started up just fine. I shut it off to save on fuel cost and went to turn it back on it wouldn't ignite. So went through the steps again and re lit the gas pilot and came on just fine but it will not innit unless I jumper it on the coil and the th side of the gas valve. I change out the therostat a couple of years ago with a compuerized thermostat with a blinking light. The light is no longer blinking. The Heater use a pilot generator to produce the the current that is neccessary to ignite the burners. I replaced the pressure swith. I put a jumper from the coil to the black lead of the pressure switch and a jumper to the th on the valve to the white wire of the pressure switch and it fires every time. Any sugeestions what could cause it to not to fire.
 

Articfox918

Well-known member
May 31, 2012
99
Western, Wisconsin
#2
I haven't worked on a whole lot of pool heaters but have worked on a few and I used to work on all kinds of furnaces (so basically the same concept w/o water) when you say pressure switch are we talking the water pressure switch or the combustion blower pressure switch? I looked up your heater and found a diagram uyou said you put a jumper on the white wire of the switch which according to the diagram I saw that's on the water pressure switch is this correct?


**EDIT** I think the diagram I found is a newer version of the one you got I will look for a different diagram the one I found did not have a pilot generator for flame proof**
 

danpik

TFP Guide
Jun 4, 2012
1,682
western NY
#3
You are obviously pretty good at knowing your way around inside your heater. With that, it should be simple enough to trace out which switch is bad. With everything hooked up as normal, one at a time unhook the switches and jumper the wires. When the heater fires up, you found the culprit. The entire proving system in these is nothing more than a daisy chain of switches similar to an old string of christmas lights (If one goes out they all go out)
 

twmackey

Well-known member
Jun 25, 2012
53
#4
Water Pressure switch. Ya I have actullay taken out the burner valve and burner and cleaned it. What bugs me is it was working fine. Some time I have to jiggle the wires to get it going and this time I tried restarting it and wouldnt ignite. I have checked all of the wires and cleaned all of the terminals and done a bunch of tests. In my own opinion it is either the pilot generator or the themastat. But with out taking the generator out or taking the half of the top off to get to the thermasta I wanted a second opinion.
 

danpik

TFP Guide
Jun 4, 2012
1,682
western NY
#7
If jumping the terminals on the gas valve makes it work them It will not be the power generator. Just to verify, it should be puting out 750 Millivolts (unless it is one of the rare lower mv generators). Easy way to verify the thermostat would be to jump across the wires to the thermostat and see if it fires
 

twmackey

Well-known member
Jun 25, 2012
53
#8
I tested the thermostat with the voltmeter and it didn't move the meter at all it just maintained the same readings. A new thermostat is $221.00 you just can't go in buy just the thermostat you have to buy the whole unit. And to answer previous questions yes I have volt meter and a manual. Not real good with volt meter but get buy. I'm going to first remove the burner tray and clean the pilot generator and then I will look towards a new thermostat if cleaning the generator doesn't take care of it. Thanks
 

Qwaxalot

In The Industry
Jun 20, 2012
439
#9
Before you do that replace all of the wire end spade connectors (you can buy 16 guage connectors at a home depot or radio shack) Corrosion at the connectors is by far and away the most common problem on millivolt heaters.
 

twmackey

Well-known member
Jun 25, 2012
53
#10
Ok here is the skinny. Changed the generator and cleaned the pilot light with a brass brush put in a brand new pilot generator in, still wouldn't start butwhen I jumpered the coil and a black wire on the Pressure Switch it started and then I could use the toggle switch to turn it off and I could turn down the thermostat, which indicated that it was a high temp electrical diode, I changed out the bad diode and put a new one in and every thing is workig great. The one thing I'm having trouble with is putting the hood on cant see to remember were some of the sheetmetal goes. I have put this lid on a couple times befor and I can't remember wher things go. Happy aout getting heater running again :-D
 

twmackey

Well-known member
Jun 25, 2012
53
#11
I put my pressure switch back on and that was not part of the problem so it boils down to a new pilot generator and a high limit diode.
 

danpik

TFP Guide
Jun 4, 2012
1,682
western NY
#12
My guess is it was the high temp diode all along. When you jumped the terminals on the gas valve and it fired up you took all of the controls out of the loop. If it did not fire up then I would suspect the powerpile.

Oh, and don't feel bad about putting the puzzle back together. In both of my past careers (auto mech and heating tech) that was the hardest part of the job sometimes. I could diagnose the problem fairly easily but getting all of the parts back on afterwards was the tough part.
 

twmackey

Well-known member
Jun 25, 2012
53
#13
I guess I need to take a picture of it when I take it apart. I'm pushing 60 and sometimes I second guess my self some times. Thanks