Do you have 24v to the coil?
What is application? Does 24v leave transformer, go to thermostat ..back from thermostat to limit or relay?
What furnace make model?
If you know 24 common...leave meter lead on common and trace 24v+ to and from components.
Do you have an aquastat to control burner (b1 and 2) and circulator (c1 and 2)?
Or is this more of a homemade system?
Thank you....do have 24v when T and T are touched with meter?
Thank you....the control is defective then.
It will need to be replaced.