Our oil fired furnace didn't kick on the other day when the temp dropped. T
his happens once or twice a month during the winter. I simply access the r
eset button and all is well (why the reset button trips occasionally is ano
ther question). In this case however, the reset button had not tripped, no
r had the breaker from the main power supply.
Until purchasing my own country home a few years ago, I lived in a large ci
ty and always rented. I have almost zero mechanical skills. Now that I've
retired and my income pared by 66%, I need to learn to do many a repair th
at until now fell to others.
In the case of the furnace not firing, I called the local HVAC repair peopl
e. The technician was puzzled. As he fiddled around with the main switch a
ffixed to the side of the furnace, the unit fired. He assumed there was a
short in that switch and after cutting power to the unit, proceeded to swap
out the switch with a new one. When power was restored, the unit continued
not to fire when called upon to do so. He then removed a cover panel that
exposed a circuit board (Honeywell ST9103A). He poked at a wiring harness
that is connected to the board (harness attached in upper right of board in
photo linked below) and by wiggling same, the unit fired. Jiggling the ha
rness resulted in the unit kicking on and off, on and off, in "fits and sta
rts" as if there were a faulty connection somewhere. He positioned the har
ness in such a way as to ensure the unit would fire (at least at that time)
, replaced the cover panel, and wrote me a bill for $164. The bill read "f
ound there to be a loose connection on wiring harness, corrected problem, u
nit running well."
While I can't argue with his assessment of the situation, I've learned to p
oke around a little myself next time before making a phone call that I know
will result in a minimum $85 just for the call.
With that said, this morning the unit failed once again to fire. I accesse
d the panel myself and by wiggling the wiring harness, all systems are agai
n GO. What is the long-term fix here? Do I attempt to replace the board (
$80 for a replacement)? Do I purchase a new wiring harness and replace tha
t? Both? Is either job very complicated? Thanks in advance for any assis
board and it should be good to go. >
Sounds like something within my abilities. I just might give it a go, thank
Any tips on how to clean the pins and connector? Pipe cleaner? Something a
bit more abrasive?
"postioning the harness" to keep it working. >
Especially knowing that eventually (probably due to the vibration that occu
rs each time the unit fires) the problem will reoccur, which in fact did ha
ppen today. They get $85 for the call and $90 per hour one on the job. Ho
w should I have handled this? He was in fact at the house for 45 minutes?
Should I have objected to the hourly rate because the fix was so simple? H
e did offer to replace the board (or at least dig deeper) at additional exp
ense to me for his time. At that point I showed him the door, knowing that
I might be able to address this myself, at 100% less in labor.
Thanks again folks.
On Friday, November 15, 2013 2:17:07 PM UTC-5, Tony Discenza wrote:
e board and it should be good to go. >
a bit more abrasive?
First I'd just inspect it. If the connector looks clean with no
sign of corrosion, oxidation, etc, then I probably wouldn't do
anything. Any auto parts store should have electrical contact
I'd look for evidence of a cold solder joint near the connector.
Those things can go for years, until finally they start to
exhibit intermittent behavior. In fact, if you can't find anything
else, I would just reflow the solder points near the connector,
assuming it's possible with whatever board design that is. Make
sure you use solder made for electronics,.
on "postioning the harness" to keep it working. >
curs each time the unit fires) the problem will reoccur, which in fact did
happen today. They get $85 for the call and $90 per hour one on the job.
How should I have handled this? He was in fact at the house for 45 minutes
? Should I have objected to the hourly rate because the fix was so simple?
He did offer to replace the board (or at least dig deeper) at additional e
xpense to me for his time. At that point I showed him the door, knowing th
at I might be able to address this myself, at 100% less in labor.
If that's the rate and he spent about that much time,
not much you can do. With some basic debuggins skills,
you can fix a lot of things like this yourself. Also, it
can be more effective, because you can catch it when it's
not working. If it's intermittent and works when the service
guy is there, it can just be a waste of a service call.
You would hope that he would have used a VOM while
wiggling the various connector pins to see if there
was a bad connection on the board. If it's repeatable,
ie hold the cable this way and it works, hold it the
other way it doesn't, it should be possible to find
the root cause.
You got robbed. The problem was not corrected and a more verbose description of said
problem should have been given and a note should have been added that the unit was
functional, but not repaired.
First, I would try to isolate the problem. Try and manipulate the connector without
disturbing the wiring.
If nothing happens, try and manipulate each individual wire with a pair of needle
nose pliers; moving left to right, up/down, and in and out. Do this at the connector
first, and not knowing if there are two connectors, then the second connector or the
solder points on the board.
So, I guess I should ask. Are there two connectors?
No, just one. I edited the photo below to identify the wiring harness in qu
With respect to your view of the way I was treated on the service call (got
robbed), it took the guy 45 minutes to identify the problem. Once identifi
ed, he did offer to continue working in an effort to correct the problem (h
e made a couple of off the cuff suggestions as to what he would do ... clea
ning the connections, looking into replacing the harness if cleaning didn't
work. At that point, at $90 per hour, I decided to take the ball into my
own hands and run with it. So, while I wasn't happy with amount of the bil
l, I didn't think I had a leg to stand on had I attempted to haggle. I sup
pose I could've beefed about paying for his time to swap out a switch that
was fine to begin with (15 minutes of the 45 minutes he was on the job) but
other than that, I understand that he's gotta get paid for his time by his
company. He made a point to tell me he didn't charge me for the new switch
and he also did a smoke test on the way out the door, showing me a clean t
est paper indicating a unit running clean.
Thanks for your reply. I'll attack the problem in the manner you suggest (i
solating the connector or the individual wire).
If you haven't soldered before and have little DIY experience, it's not
easy to advise you to pursue technical solutions. Here's something easy you
can do. Buy a can of electrical contact cleaner (Radio Shack, most hardware
stores). Turn off the power to the furnace. Disconnect the offending plug.
Spray the connector at the pc board and spray the plug connections. Now plug
and unplug a bunch of times with some wiggling action. If you are lucky you
will remove the corrosion that is causing yur problem. Now plug the plug in
firmly. Restore power and hope for the best.
If that doesn't work I'd recommend finding an honest competent repair
Another thing to do is, as suggested, disconnect all power, and remove
the board from the chassis, and look at the back side of the board where
the connector is. Look for burnt traces.
Usually these connectors (Molex) are of a bullet type of terminal inside
the housing, where the board side as metal tubes that the plug side, which
has split tubes, that slide over the metal tubes on the board side. The
clamping strength of the connector side will weaken over time and sometimes
you just need to get a small, metal object (ice pick) into the Molex and
gently pry them closer together so that they may make better contact. Of course,
follow David's instructions, also.
When I replaced a board on my old z Carrier furnace a pig tail
cable extender was inclded with the replacement boards. It had
M connector at one end and F at the other. Just to make the
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