Troubleshooting modules

Doug_12

Hey folks, I am new to this industry and learning as I go. I really do not have that much experience yet. I do have a question though. On package units, gas/AC rooftops and home boilers, is there a specific way to troubleshoot the electronic module? Thanks for your help.

Doug

bigugh_4

Ther is and there Ain't

a specific way to troubleshoot electronic moduels. Most manufactures have their own specific way to go about this. Usually printed in the manuels that come with the units. But you must have a basic idea of what has to happen to get the unit going. That is where experiance comes in. troubleshooting is a combination of these two areas. Get Training is experiance gathering. Then there are the supporting components of the system, many mechanical, that must behave to have the electronic box do its thing. Good luck

gary_6

You should look to take Timmie McElwain's courses they are very helpfull.

[Deleted User]

modules

There are hundreds of modules out there. You need to go to the equipment manufacture or better yet, the module manfacture. They usually have a procedure you can follow to see if the module is good or bad. I see more and more that some modules have LED lights that flash to advise you of what the problem with the unit is. I always try to check this first before power is shut off..Sometimes shutting off the power will reset the module and erase the memory.(SAFETY FIRST..BE CAREFUL AROUND POWERD EQUIPMENT AND HAVE SOMEONE NEAR-BY KNOWING WHAT YOU ARE ABOUT TO DO)

Dale

Black boxes

Some of the really large rooftops have rather complex troubleshooting criteria having said that to trouble shoot any module you need to know what outputs are expected from what inputs. While this sounds simple it isn't, but it is IMHO the only way to feel comfortable troubleshooting electronics. For instance on a simple older gas furnace ignition module the output is usually what's not noticed or you wouldn't have been called. So say the pilot is sparking but there is no pilot flame. You know the needed input of 24 volts to the box is there or the spark module wouldn't spark, we expect the output to be 24 volts out to the gas valve pilot portion, if we have it the box is OK so far. If we don't have the expected output with the given input we need a new box. If the pilot was lit but no main burner on the simple box we know the Mv and C out put should come in sequence after the pilot is lit. So with one input we need 3 outputs, spark generated, pilot valve terminals powered and then main valve powered. Some of the new boxes need a constant 24 input at the 24 and 24 terminals. Tthe variable input ( perhaps 24 hot from the stat or pressure switch output ) that starts the sequence must come to the TH terminal. However it's always inputs that must be there and outputs that follow.

[Deleted User]

modules

Forgot to mention...also check for a good ground connection both at the module and at the pilot burner. Very critical to prove the pilot circuit. Take apart the pilot assby. and use sandcloth to get a good ground connection between the pilot mounting bracket and what it mounts to..

MikeB34

Sequence

It is all about sequence of operation. If you know what happens in what order, you can determine where it stops. As mentioned before, if you know where it stops, you can check the appropriate inputs and outputs of the box. Right input and output = box ok, component problem. Input ok, wrong/no output = box problem. ALWAYS check the inputs. check for power to the load, the load itself, and any switched to the load. Also known as PLS (power,load,switch) troubleshooting)
Experience is the best teacher.
Good luck.
Mike

tim smith_2

troubleshooting

All ignition modules have a flame signal rating, usually in micro amps. If the pilot lights but does not bring on main, then you can usually check for flame signal as long as it has a seperate flame rod from igniter. You have to set your meter to m/a. micro amps in other words. disconnect lead to flame rod and put one lead of test meter to lead and other to flame rod connection. Normal readings depending on mfr is .7 appx to 5 ma. Most of the time it is a dirty pilot or poor burner ground that causes flame failure to occur. Other problems are cracked porcelain on flame rod, or dirty rod. If pilot not lighting but spark present, may have a poor gap on igniter, leak to ground from lead or cracked porcelain on igniter. This is just a portion of the causes for failure to ignite. Talk to the local Honeywell distributor about upcoming classes and take some, will help alot.

MikeB34

sandcloth...NOT

DON'T use sand cloth. It leaves a residue of sand, which when heated will turn to glass..and glass is an insulator. It may work for a bit, but you WILL get problem. Use steel wool - fine grade ONLY.

Dale

Steel wool

I think steel wool leaves residue behind also, we use scotch brite pads and they seem to work well.

MikeB34

yes but...

steel wool (the pure stuff, not sos pads) only leave a metal residue. Will not deteriorate the flame signal. We are talking MICRO amps, and a little resistance can quickly kill your signal. Scotch brite pads work ok too. But no files, sandpaper etc... (Ilove this site!)