One of four dials doesn't spark ignitors...

Clean the wires going to the ignitor of each burner, clean the burners as well. Chances are you have too much oil and dirt on them that is why your burners are not igniting.

Test the ignitor first, if the ignitor does not spark should be the ignitor itself.

Can have below issue.

(1) Electric current is not reaching the ignitor. (wire is broken or have a leak)
OR
(2) Having problem with ignitor. (need to replace the ignitor)

Hi,

Here is a tip that I wrote that will help figure out why the burner spark keeps on clicking...

Gas Range Repair Burners Keep on Clicking

heatman101

There are three parts to the ignition system typically.

The ignitor that is either in the burner or outside the burner.

The spark ignitor switch that is located on the burner control. (( one for each control ))

The spark modual. the modual creates the hi-voltage spark.

If the burner that does not ignight with its control does not spark but does spark with one of the other controls then the spark ignitor control switch is bad.
You can test it with one of the other burner control knobs. (( just try a working burnder and when it clicks look at the bad burners ignitor and look for the spark.))

If the bad burner that wont ignight does not spark then either your modual is bas or the ignitor is shorting out.

If you see any little spark but it does not spark from point A to Point B like the other burners then your ignitor is shorting and should be replaced.

If your ignitor is ceramic and it is cracked, then it should be replaced.

Electric gas igniters sometimes get stuck in one position causing a clicking sound. The clicking sound that you hear is the electric arc that is pulsing from the igniter conductor (wire) to ground (the gas burner). It receives power from the electrical outlet that the stove is plugged into.
Residue from food and sometimes cleaning products may be preventing the igniter from producing a spark (Arc) to the base of the burner. This is a common problem that occurs when the stove has been cleaned or food is allowed to build up. Make sure that the igniter and the burner base are clean and dry. This will help with proper operation. Oven cleaner and a small tooth brush may be used to accomplish this. Another problem with ignition may occur if you have too little (touching) or too much space between the igniter and the base of the burner; it will prevent the burner from igniting. You should only have a little more space than the thickness of a nickel between the burner base and the igniter. A good “blue” arc from the igniter to the burner base is optimal. If this doesn’t work, you may need to replace the electric igniter module. Good luck.

I am going to assume you hear the "clicking" sound when you try to light the burner.
open the top of the stove. there are four burner. look at the one that is not lighting. use a straighten paper clip open the holes that is directly in-front of the tube that is facing the center of ignitor.
also make sure that the air vent directly behind the knob is fully open.

It is sparking because the module does not sense the heat which would normally cause the sparking to stop.

It can be caused by a poor ground, make sure the ignitor at that burner is clean and free from any obstructions. If it is then it could either be a defective ignitor or spark module.

I have a Thermador Gas Range PG364GDBS - Oven, 4 burners, and center griddle. All are gas. The four burners and gas oven work fine. The griddle just stopped working, no spark. Turning on the griddle control, the gas valve opens(hear it), gas flows (smell it), but the ignitor will not spark (no loud or faint spark that I can hear). I got a replacement ignition device (mount at the burner) thinking it might be the problem, but still no spark. I checked the AC voltage at the terminal and measured 39 VAC between the terminal and ground. Not sure if that is the correct voltage. Any insights or advice would be great.

Sounds like you have a bad ignitor on that burner.