On Saturday, March 23, 2019 at 4:09:26 PM UTC-7, Joerg wrote:
On 2019-03-20 09:42, wrote:
On Tuesday, March 19, 2019 at 1:28:01 PM UTC-7, Joerg wrote:
On 2019-03-19 11:17, wrote:
A couple of months ago when it was coldest my central heating
stopped igniting. My impression from the sounds it was making was
that the thermocouple was bad or the pilot light that would be
ignited was dirty or some such so that the flame wasn't close
enough to the thermocouple of inform it that there was a real
flame there and turn the full flame on.

The repairman came out and said that the pilot and thermocouple
was OK and changed out the main gas valve. The heater appeared to
work for six weeks and then as the weather got cold again started
not lighting again.

The company sent another repairman out and he said that it was
the main control board and replaced that.

I am now $1,600 into "repairs" and sure enough - the heater
isn't lighting still.

It would appear to me at this time that there is nothing more to
replace but the pilot tube and the thermocouple. So I wonder how
to convince the repairman that there is something wrong with one
of those?


We had that happen a long time ago and the cause was the
electronic controller board. The central propane furnace would go
VROOOOP .. PHUTAH-PHUT ... RUMBLE ... VROOOOOOOOOP ... and never
stayed on anymore.

When the technician came out he exclaimed "Oh look, an old Fenwal
controller board!", saying he was amazed that it lasted this long.
He switched it out against one from another manufacturer and all
was well.

I asked him to leave the old board and when probing it I found that
the triac that controls the main burner valve had gone partially
bad so it wouldn't be able to send a full current through the valve
solenoid anymore. Could have kicked myself because instead of
paying a few hundred Dollars I could have gotten one of those triac
for a couple of Dollars and replaced it. If these triac are on a
separate driver board then check that.

There is also a suction sensor, for example a flap in the intake
stream that operates a signaling switch. If that got crudded up it
might at times falsely signal a failing air draft and that would
cut the main valve.

-- Regards, Joerg

http://www.analogconsultants.com/




when the technician came out again the board was showing errors of
"too many tries". He pulled the connector off and spread the male
connector so that it would make better connection to the main gas
valve and it appears to work perfectly now. Though when the main gas
valve was replaced 3 months ago it all worked fine until recently.


The first technician could have diagnosed that easily by measuring how
many volts are actually arriving at the solenoid. This is the first
order of business for me when, for example, my wife says that a certain
zone in the yard doesn't get watered reliably.

--
Regards, Joerg

http://www.analogconsultants.com/

He got the correct readings because the problem wasn't the board but the connection between the board and the gas solenoid not making proper contact. Since both the board and the valve were new there really wasn't any question about their working. It took him a little while to isolate the connection.. These connectors are the male and female pin types. So it is virtually impossible to measure them when connected.