This is a Comfortmaker Unit that reaches thermostat that goes through the ignition sequence and will run to meet thermostat call temp. The problem is that it constantly short cycles about every minute during the heating process until the temperature is met. Strangely there is no Flame Sensor but has a combination igniter sensor onboard. I've already attempted cleaning to no avail. .There are no LED's on the board so troubleshooting is difficult. If the igniter works is it possible that the sensor portion has failed? Or could it be the Ignition module S8600M or board that's the culprit? Any assistance would be appreciated.

 

Welcome to the forums.

It's better to keep problems in different threads to eliminate confusion between members.

You'll need a voltmeter. Check from 24v to 24v ground...... terminals 5 and 6 on the S8600M for 24vAC. If it's there and the flame drops out..... it's the ignition module or pilot assembly. If the power drops out.... it's a thermostat or limit or power damper or anything else in the 24v line supplying the ignition module.

 

Hi thank you so very much. I apologize as I am new to the site and couldn't figure out how to start a new post. Update: Followed your advice and 24v drops out at the S8600M when the flame drops out. Pressure and limit switches are opening when flame on so the only thing left is the board.

 

If the 24v drops out AT the S8600m then the problem is before the module.
You need to trace the 24v line from transformer to the module to see what is opening.

Look for a wiring diagram on a service door. Take a picture and post it.
How-to-insert-pictures.

 

 

You need to follow the blue wire from the six pin plug to the ignition module. It goes thru two to five switches. Different with every sub model. One of those devices is opening and causing the loss of 24v at the ignition module

 

Hi, thanks for the great response. Traced the blue 24v first stop was the pressure switch. I had checked it previously to be good but took a chance at using a jumper and that solved the problem! I'm going to replace it and update if it solves the problem.

 

The pressure switches are 99% reliable. Usually if it trips.... something in the flue is incorrect or plugged. Also check the connecting tube and at each end. Their could be a very tiny metering hole that can get plugged.