how to tell if an ignition control module is bad

billtang

new Igniter was not getting 110v from the ignition control module (fenwal 2465H 600-003 or 35-655-600-003). When the call to heat comes, the motor runs. There is supposed to be 110v from control module to igniter (which I measured once when it was working) but it is not there. After 45 seconds there is a 24v to gas valve and a click. The valve opens but since there is no flame, it is then 0v and shuts off. During the whole time, the red diagnostic light stays on. According to the spec, this is supposed to be "Internal Control Failure". Does it mean this control module is bad? Thanks!

Intplm.

Igniter ? New as in installed today ? How long has the igniter been in operation? You might mean to say "Ignition module".

billtang

The hot surface igniter is a few days old. The resistance is 70ohm. I just replaced one which is of 100ohm. Although that was just a few months old, it is above the 40-90ohm range; according to many online articles, anything above 90ohm is not reliable.

The ignition control module (fenwal 2465H 600-003 or 35-655-600-003) is about 12 years old.

The wiring has not been changed. I check common ground to be ok (within 2ohms).

Intplm.

I hate to say it but it might be toast.
Was this a direct replacement?
Or
was there a different ignition module in there before?
If so? Why did you need to replace it?

EBEBRATT-Ed

Yes. Sounds like the ignition module is bad

billtang

Thanks for all the feedback. The issue with this module is that intermittently it appears to unable to maintain 110v to the hot surface ignitor upon call of heat. Interestingly when it works, the red led diagnostic light also stays on. So I wasn't sure.

billtang

Finally bought a replacement. It is slightly different with three tries instead one try (35-652505-003 vs 35-655600-003). It seems to work much better.

Previously, the system works one out of about ten times at the worst case. Now it is much better, mostly ignites and stays on with the first try.

HVACNUT

There should be ignition the first time, every time. Something else is going on there if it keeps losing 120v to the igniter.
Check the pressure switches, hoses and their negative pressure vent and drain port bungs.
Also check the drain itself.
There will only be drain parts if it's a condensing furnace.

DZoro

Igniters draw a lot of energy. Double check all main power wire connections. A loose or poor connection will cause issues. Follow the wiring right to the electric panel. The only thing on that circuit should be the furnace. If there is anything else that can cause issues. No lights, outlets or other.
D

Intplm.

Sounds like you might have a short or intermittent short. And as @DZoro said.
Make sure this is on a dedicated circuit.

Jamie Hall

And while you are checking the wiring, check the ground as well. Often overlooked -- but you must have a solid ground back to the panel independent of the neutral.

JUGHNE

If the fire does not stay on all the time then:

if you have a separate flame sensor rod, it may need cleaned.
Also the burner must be grounded for the flame sensor to work.
There may or may not be a separate ground wire for that function. Often the burner itself is assumed to be grounded.
If wire is there check or reset each end of it for good continuity.

HVACNUT

Looking back, you never mentioned the make and model of the furnace.
Also post a pic of the wiring diagram if you can.

I recently serviced a 90+ furnace that was losing 120v to the HSI. Looked like someone erratically playing with a dimmer switch. Condensate backed up into the inducer fan housing and the water and fan were wreaking havoc with the vent pressure switch.

Suey

Is there a universal ignition module that can replace the Fenwal 35-655-600-003? They seem to be getting more expensive to come by.

EdTheHeaterMan

I'm lost on this question because the original post is for HSI ignition but the part number is a Direct Spark ignition module.

Suey

I stumbled upon this post because of the ignition control module. I own a building which has 36 units which use these ignition control modules. Would like to keep a few on hand for when the modules go bad. I've already replaced a few throughout the years so am hoping there may be "universal modules" (where you can set the dipswitches to get the proper timing, etc)

EdTheHeaterMan

The Honeywell version seems to be the same price or higher. (S87...)
Direct Spark ignition systems are more critical in proving ignition quickly, so the electronics inside are more expensive.
HSI systems are a little less expensive (S8910...)
And finally, the Spark to pilot controls are the most economical. (S8610...)

Here is a cross-reference chart for gas controls.
https://controlscentral.com/Portals/0/Honeywell Controls Cross Reference.pdf