Does the difference in resistance matter if you replace a 24-inch 30mv
thermocouple that has a thermal switch versus one without the thermal
I bought a generic Honeywell 30mv 24-inch thermocuple (PN CQ100A1013) from
That picture in the URL above is wrong because it's 24 inches:
When I went to put it in the hot water heater, I belatedly realized the
original thermocouple has an integral thermal switch.
I know the length matters, from a resistance standpoint, but the hardware
store owner had never heard of a thermocouple with at thermal switch
The thermal switch is a safety feature that will shut down the pilot if the
heat under the hot water heater gets too great:
When I call Sears in San Jose at 408-274-2593, they confirm the part number
is PN 9000056015 but that replacement part doesn't seem to have a thermal
switch on it.
Have you ever had to make the decision of whether to replace a thermocouple
that had a built-in thermal switch with a generic thermocouple that had no
thermal switch? Did the resistance match?
On Friday, August 19, 2016 at 7:16:55 PM UTC-4, Danny D. wrote:
I'd say the resistance doesn't matter because there probably is no
material difference in resistance. But without the thermal fuse,
whatever safety that it provides is gone. In other words, it should
work, but without the additional feature. Does it? I guess the
question comes down to is what you wind up with the same as my WH
and most others that don't have this or does my WH and others have
some other way of thermal cut off instead that yours doesn't have,
thereby leaving yours unsafe? IDK
On Fri, 19 Aug 2016 16:33:50 -0700 (PDT), trader_4 wrote:
The book resistance of the Honeywell CQ100A1013 thermocouple is apparently
0.2 ohms but that's all I could find out by way of technical specs from
either Sears or from Honeywell.
Sears confirmed the replacement part number is 9000056015, but when I look
up *that* part number, none of the pictures show the thermal switch.
The fit of the Honeywell CQ100A1013 "universal" thermocouple isn't even
close to the same as the original fit either as the mounting for the
original is screwed on with a plate while the "universal" Honeywell
thermocouple is a screw on nut which doesn't have a corresponding mating
Therefore, the "universal" thermocouple isn't even close to universal,
although I can probably bend some metal to make it fit - I'm basically
making my own parts out of raw materials.
When I called Honeywell technical support at 800-468-1502x1x1x9x1 to find
out if they have a closer replacement than the Honeywell CQ100A1013 that I
bought, they drove me nuts in so much as they don't even understand the
simplest thing about the product they sell.
All they could tell me is that it has to go 1/2 inch into the flame.
When I asked for a thermocouople with a theroswitch, they told me to use
the Q340A1074 but that doesn't seem to have a thermoswitch either.
So I'm basically making my own parts from raw materials because the mounts
aren't even close on *any* of these so-called replacement thermocouples.
On Sat, 20 Aug 2016 01:21:37 +0000 (UTC), Danny D. wrote:
I concluded the "universal" mount stood zero chance of fitting.
There is just no way a "universal" thermocouple is going to stay put there.
Just look at this bracket for my original thermocouple.
For now, I sandpapered the thermocouple and put it back in, but I think
I'll either have to find an exact replacement or build my own bracket
I can't believe everyone runs into this fit problem.
According to this A O Smith webpage, see page 18 at
"the thermocouple is not a separate replaceable part."
"There is no routine service associated with the TCO"
"The TCO is an integral part of the thermocouple and
not replaceable as a separate item. A pilot burner assembly must be
See picture and instructions on page 20
Not knowing your specific model & serial numbers, 2 possible parts are
P/N's 9006013005 or 9006014005
On Saturday, August 20, 2016 at 8:24:15 AM UTC-4, Retired wrote:
You left out the best part. One of those is $117, the other $144!
What's a regular TC cost? $15? Looks like they changed a design
from a cheap, common TC to this thing that costs 10X. How much
additional protection it provides, is it really necessary and/or
worth it, IDK. All I know is they were making WHs for how many
decades with the old style and I didn't see any widespread carnage.
I thought the biggest issue was either blocked flues generating
CO or idiots using gasoline or similar solvents in close proximity.
On Sat, 20 Aug 2016 06:04:33 -0700 (PDT), trader_4 wrote:
After calling the AO Smith residential support phone number at
800-527-1953, I found, after giving the nice lady my serial number, that
the part number I need is the $88 MSRP pilot assembly P/N 9003455005.
Unlike cars, I have found out that MSRP is generally *lower* from the
manufacturer than the parts suppliers in San Jose, so I expect it to cost
more if sourced locally.
Even so, I called the dealers she suggested, only one of which was open on
a weekend, who himself, no longer sells AO Smith parts. So I'll have to
wait for the weekend to find price and availability at local sources.
Googling, the pilot assembly seems to be a whole bunch of stuff:
On Sat, 20 Aug 2016 16:59:13 -0400, Tekkie? wrote:
Just to report back, the sandpapered thermocouple has been working, so I
have time to order the correct parts, probably from AO Smith themselves as
they have an order number for parts:
When I buy the pilot assembly, should I buy an anode?
I have hard water (calcium carbonate rich).
How often do you replace your anodes?
On Monday, August 22, 2016 at 12:40:55 PM UTC-4, Danny D. wrote:
I don't. There are two competing theories on this. One is that replacing
it will extend the life. The other is that the tank is still going to fail
at about the same time from other effects anyway. If you want to replace
it pull the old one part way out to see how much is left, do that
every few years to keep an eye on it. I just went the lazy route. So
far, about 15 years on a garden variety State.
On Mon, 22 Aug 2016 16:07:20 -0400, Tekkie? wrote:
You have a point on the shipping, as the anode is long I presume.
Mine has the hot-water nipple on the end also.
I checked three parts stores.
None had it in stock while most had the pilot assembly in stock.
So, people replace the AO Smith pilot assembly more so than they do the
anode (or they use a different anode part number).
- pilot assembly 9003455005 $88
- anode with nipple 9009148005 $38
*If* you can remove it; there's very little of the aluminum or
magnesium rod still left, and you can see the supporting wires.
You should be checking the anode every year or two, this also keeps it
from corroding in place, so you *can* check it.
Also, IIRC, it uses a large socket (1-1/8"?) and a long 1/2 drive breaker
bar . They are usually very very tight. Just drain a little water out
(gallon or so) and still you may need an extra hand to hold on to the tank.
You will need some clearance above the tank to put the rod in.
On Mon, 22 Aug 2016 16:26:25 -0700 (PDT), trader_4 wrote:
Thank you for bringing the vertical space up as a problem, as I might have
that problem since the hot water heater is in a relatively small closet,
and it's on a pedestal off the ground.
I never thought of that problem until you mentioned it.
I removed mine when the tank was about 5 years old. It took a large
pipe wrench (the hex top of the rod was above the tank) and a 3 foot
or so section of galvanized pipe on the wrench handle and lots of
effort to remove it.
On Tue, 23 Aug 2016 20:08:45 -0000 (UTC), Jerry Peters wrote:
I had a spare hot water tank to practice on and it was 27mm and it took a
very long pipe (about 8 feet) to twist it off.
So, those things are in there rather well if they're not removed every once
in a while!
On Mon, 22 Aug 2016 20:19:12 -0000 (UTC), Jerry Peters wrote:
This makes a lot of sense to remove the anode yearly so that you can remove
it before it corrodes in place.
Unfortunately for me, the AO Smith anode (PN 9009148005) comes with the
hot-water nipple, so, they have it inline (somehow) with the hot water
Seems silly to me that I have to basically disconnect the water pipes just
to check the anode.
On Tuesday, August 23, 2016 at 8:12:40 AM UTC-4, Danny D. wrote:
Between that thermal fuse at the burner and the screwy anode that's
part of the water pipe connection, I've heard enough to stay away
from AO Smith. It looks to me that they are doing things in a
way to force you into parts that you can only get from them. Bad
for two reasons. Your thermocouple goes from a $15 part that you
can easily get many places, including locally, to a special part
that costs $130.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.