Payne 394JAZ048065AAFA

[Marcus]

My first time ever touching a heater, so here goes. Over at my dad's house -  turning on the heat at the thermostat will cause a flame at the pilot - lasts a few seconds at best, then goes out. (Unknowingly I was doing a good thing by occasionally un/re-plugging it. As I've learned here, that resets the Igniter/lockout) One time in ten it went all the way to igniting the burners for about 10 seconds but then it all went out. I increased the pilot gas flow but it still wouldn't hold. I've also un/re-plugged all the electrical wires, except for the high voltage one. Does it even have a flame sensor?

Some part stats: Igniter/Lockout = H86WZ512A - not too sure about the 'H86' part but it looks like your IGM33WZ512. Pilot assembly looks like your 3 wire PIL680005A + PIL680512.

What should I try next - now that I know just a little bit more?

[hvacdrd]

The pilot sensor is a bi-metal switch that makes and breaks a set of contacts as it heats up.

Using a volt-meter, test from Yellow to White at the 3-wire pilot switch molex connector(still connected). Voltage should be 24VAC on the initial call for heat then switch to 0VAC after 45-60 seconds, then the main gas valve is energized. If the reading stays at 24VAC then the bi-metal switch is not closing properly.

Removing the pilot assembly & cleaning the pilot hood and orifice should may take care of it. If not replace the 3-wire pilot assembly.

As always only perform the work if you are confident that you can recognize and repair potential hazards.

[Marcus]

Went back to dad's but forgot my DMM. Decided to do a bit more testing just to confirm the situation. So I removed and cleaned the Pilot Electrode Sparker and put it all back. In 10 tries of unplug/replug the 110 supply and turning it on at the thermostat I didn't see a single spark. Just a click sound from the Ignition Module. Come to think of it, most times last night was the same way - just a couple of spark/pilot flame then nothing.

I see 3 parts in play here - the Ignition Module, the Pilot Safety Switch and the Pilot Electrode Sparker. How do I determine which is faulty?

Is there a way I can test the Ignition Module? The Sparker?

Should I go ahead and do the aforesuggested 24VAC test at the 3-wire pilot switch molex connector?

[hvacdrd]

I jumped the gun assuming the pilot was lighting. The sequence is as follows on a call for heat...

Inducer(exhaust) motor starts

Pressure switch contacts close

If pilot switch contacts are closed (Yellow-Green) Pilot valve, spark module and lockout timer are energized

Pilot ignites, main valve should energize in 45-60 seconds.

Not sure on the lockout timer, maybe 5 minutes if pilot does not prove.

So start at the Yellow wire(at 3 wire pilot connector) after the inducer starts. Check for 24VAC from Yellow to Common. If you have power here we check the pilot switch, if not we look at the pressure switch.

Info that would help - Is this a 90% furnace?(does it vent out in PVC piping?)

[Marcus]

Well I had to shove some wire into the existing sockets to check voltage across yelllow and white (I'm sure a pro has an adapter or something at the molex) and got nothing. Kind of hard hitting the on switch and running to the garage to check. Best I'll get, once in a while, is a click sound from the Ignition Module; no spark.

I've never seen an exaust fan in CA - only one for forcing the heated air into the heating vents, which kicks on about a minute after the mainburners ignite.

What's a pressure switch?

"Vent out to PVC piping" - I'm sure you don't mean the flame exaust, it joins the metal hot water heater exaust pipe. I believe his heated air is distributed through metal ducting; mine goes through flexible insulated tubing - don't know if it's PVC.

What's next?

[Marcus]

Whoa! Hold the phone. I'd like to start this thing all over. During my prior testing I'm sure I didn't have good connection of my Digital Multi Meter. Also, I've found a better way of testing, thanks to some education posted here. Before I was turning on the thermostat and running to the heater - missing the beginning of the sequence. Now I just leave the thermostat ON and un/replug the 110 plug right at the heater and am seeing everything - and getting consistent behavior. Here goes:

With the thermostat ON and my DMM connected to yellow and white I plug in the unit.

I get 24VAC, sparking and pilot flame. After about 3-4 seconds I hear a very low thunk and out goes the pilot flame and voltage goes to zero. Unplug for 10 seconds, plug it in and this repeats - consistently.

My guess is the pilot sensor is bad and is probably part and parcel to the 3-wire pilot assembly. But I know nothing HVAC and need someone to tell me what's what - HELP!

I do hereby promise to never read someone else's heating problems and offer any suggestion.

[hvacdrd]

Good job testing the pilot switch. It is doing what it is designed to do since the voltages are correct in the sequence. The gas valve is designed with an internal pressure switch with proven pilot. Once the pilot solenoid is opened the pressure switch closes & "holds" the circuit.  I'll do some checking to get you more information so we can confirm that the valve is bad.

Ok, here is a diagram of a valve that is typically used on the Carrier 3-wire pilot system, let me know if this is what yours looks like. It should have 5 terminals.

[Marcus]

I think I know what you're talking about - it is physically and electrically between the Ignition Module and the 3Wire Pilot Safety Switch. That's actually where I attached my DMM to ground (white wire) and got the 24VAC reading.

This site, under "Gas Valves - Payne" there are 3 that look like it. Mostly for the light blue ON/OFF gas switch and adjacent pilot adjuster. I notice that Code: GSV32CW183A  lists as compatible to my furnace model - 394JAZ048065AAFA.

I'll go back tomorrow and visually confirm.

Thanks!

[hvacdrd]

Here is a link to the 36E93-304 that I was referring to. The pressure switch is internal to the gas valve.

[Marcus]

Yes, it does have 5 electrical terminals enumerated just like in the picture:

http://americanhvacparts.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=GSV32CW183A&Category_Code=gv-payne

Wires:

5 - Brown

1 - White

4 - Yellow

2 - Black

3 - nothing

It has "#EF32CW183A" on it.

[hvacdrd]

Ok, I finally found what I was looking for.

To test the valve internal pressure switch - remove the yellow wire on Terminal 4 at the gas valve(making sure the connector doesn't touch anything). Using your ohm-meter you will be testing from #4 to #5 during the first 10 seconds of the furnace starting. With power off 4 to 5 should read open (infinite). Upon power up when the pilot lights the reading should change to 0 ohms. If it does not, the internal switch has failed and the gas valve needs to be replaced.

You can use the White Rodgers part# 36E93-304 or equivalent.

[Marcus]

OK, its been some time since I've poked at this. My dad passed away and there hasn't been much need for heat. But I've still got to get this fixed.

After leaving it unplugged for months, I turned it on at the thermostat and plugged it in - I got pilot flame and main burner! But after a minute, just about the time the fan should have kicked in, it all went out. I know the fan in the FAU works as it runs with the A/C and when I turn the fan switch from AUTO to ON it blows.

I unplugged for 5 minutes but I got nothing. Next day, I got nothing - not even the pilot flame.

Does all this still pint to the White Rodgers part# 36E93-304?