[surferdude2]

I have to share my unattended monitor system I use for systems that have intermittent problems that can be caused by one of the various safety switches in modern systems triggering random shutdowns. It's not a substitute for a Tektronix digital scope with single shot recording but it doesn't cost 4 grand either.

I sacrificed an old Christmas tree light string and made a few "Test Lights" using the sockets and the pigtails they provided and put some small insulated alligator clips on them.

Since they have 2.5 volt bulbs in them, which is standard for a 50 bulb series incandescent string, I connect these across any suspected normally closed switch, such as roll out, high pressure, low pressure, high temperature... etc. that can open to cause a system shut down. If the switch opens, this poor little bulb becomes a tiny flash bulb, never to burn again. You can even use it on a normally open pressure switch if you hook it up shortly after startup but would only be good for one session of course.

I can go about my other business and still know which/if any of the safety switches caused the shutdown. I can leave them connected for days at a time waiting for the elusive intermittent problem to sneak up once more.

Now I'm not saying that means the device that blew the bulb is the problem, but it can point me in the right direction. Sure, you can use any error codes that a sophisticated board may be generating but some boards don't do that and sometimes you may not have access to what the code means. There are applications beyond HVAC as well.

I used another version of this same logic one time to see which parking lot light, on a string of 4 that shared the same circuit, was intermittently shorting and tripping the breaker. I put marginally rated fuses in the load line of each light and voila! The one that blew the fuse turned out to have a bad striker in it that was going bonkers on rare occasions and causing the ballast inrush current to overload the circuit just enough to trip the branch breaker.

These methods may not be for you but they have saved me lots of time and allowed me to fix things that the other guys couldn't do. That enabled me to make the big bucks and retire and while away the hours on some DIY site. :biggrin2: And yes, I did have a Tektronix scope but I saved it for the rare occasion when the light Christmas light method failed me... not often

You sometimes have to take unusual measures to diagnose unusual problems. I think the best diagnostic tool available is often right between your ears. My grandpa used to put a horsehair on the doorknob of his blacksmith shop to see if anybody was in the shop while he was away. I always wondered how he knew I was in there... he never revealed his method until I was fully grown and we laughed about it. I miss him.

Thanks for reading if you made it this far.

Best regards, SD2

 

[user_12345a]

Don't many modern control boards store fault code history?

If they ever ban incandescent christmas lights you won't be able to troubleshoot like that any more. Better stockpile them. :biggrin2:

 

[yuri]

James Bond used a hair off his head to see if someone broke into his room/spied on him in Dr. NO.:glasses:

The higher end furnaces have boards that store 10 fault codes. The basic ones don't.

 

[BayouRunner]

I have to share my unattended monitor system I use for systems that have intermittent problems that can be caused by one of the various safety switches in modern systems triggering random shutdowns. It's not a substitute for a Tektronix digital scope with single shot recording but it doesn't cost 4 grand either.



I sacrificed an old Christmas tree light string and made a few "Test Lights" using the sockets and the pigtails they provided and put some small insulated alligator clips on them.



Since they have 2.5 volt bulbs in them, which is standard for a 50 bulb series incandescent string, I connect these across any suspected normally closed switch, such as roll out, high pressure, low pressure, high temperature... etc. that can open to cause a system shut down. If the switch opens, this poor little bulb becomes a tiny flash bulb, never to burn again. You can even use it on a normally open pressure switch if you hook it up shortly after startup but would only be good for one session of course.



I can go about my other business and still know which/if any of the safety switches caused the shutdown. I can leave them connected for days at a time waiting for the elusive intermittent problem to sneak up once more.



Now I'm not saying that means the device that blew the bulb is the problem, but it can point me in the right direction. Sure, you can use any error codes that a sophisticated board may be generating but some boards don't do that and sometimes you may not have access to what the code means. There are applications beyond HVAC as well.



I used another version of this same logic one time to see which parking lot light, on a string of 4 that shared the same circuit, was intermittently shorting and tripping the breaker. I put marginally rated fuses in the load line of each light and voila! The one that blew the fuse turned out to have a bad striker in it that was going bonkers on rare occasions and causing the ballast inrush current to overload the circuit just enough to trip the branch breaker.



These methods may not be for you but they have saved me lots of time and allowed me to fix things that the other guys couldn't do. That enabled me to make the big bucks and retire and while away the hours on some DIY site. :biggrin2: And yes, I did have a Tektronix scope but I saved it for the rare occasion when the light Christmas light method failed me... not often



You sometimes have to take unusual measures to diagnose unusual problems. I think the best diagnostic tool available is often right between your ears. My grandpa used to put a horsehair on the doorknob of his blacksmith shop to see if anybody was in the shop while he was away. I always wondered how he knew I was in there... he never revealed his method until I was fully grown and we laughed about it. I miss him.



Thanks for reading if you made it this far.



Best regards, SD2

I always tell my techs sometimes you have to think out of the box. Creative thinking will definitely make you a better serviceman. I like your method for those rare ones


Sent from my iPhone using Tapatalk

 

[yuri]

I will sometimes stop/start a furnace 20-24X in a row to try catch intermittent problems.

If the customer says it fails once or twice every day/24 hrs and the furnace runs 2-4X per hour in very cold weather then the odds are that I can simulate the odds of it failing while I am there.

I jumper R to W with a jumper wire with alligator clips and do that 5 X and then with 5 mins for the blower motor to cool off.

95% of the time I catch a sticking gas valve or inducer motor relay. I t is slow and tedious but better than having to drive back later and do it anyway.

 

[surferdude2]

Yuri, You and I were likely trained at the same school, the school of hard knocks! First we tried to learn the trade. Then we tried to make money in the trade. Then we tried to do it faster and actually make a living in the trade. With the volume of business increasing, experience developed into a few tricks learned along the way to make the bottom line fatter and put a higher grade of meat on the table. If you get good enough, you can have tenderloin frequently!

I've been guilty of smacking some intermittent item with the butt of a screwdriver to see if something mechanical was at fault rather than somethings electronic. I flex live printed circuit boards with a wooden dowel or a pencil to see if there is a response that would indicate a physical connection failure that is dynamic and possibly intermittent.
When I had a TV repair shop, the other repair shops brought their "Dogs" to me for bench repair. I often used a spray can of freon and a hand held hair dryer for a heat gun when troubleshooting those evasive thermal intermittent problems. On and on it goes...

Inflicting trauma on equipment can be used effectively if applied by an experienced hand (works on people too occasionally) . Knowing where to hit and how hard comes from years of experience. Knowing how much to heat and cool to test a component is important also. I always loved sophisticated test equipment and spent hundreds of dollars on it. Even so, it didn't make me as much money as the bag of hot licks I got from experience.

Regards, SD2

 

[yuri]

I messed around with a Honeywell Idiot valve when running/firing and interrupted it by jiggling it.

Then it flamed out AND fired up B4 the valve completely dropped out and flashed back/blew back at me like a bomb.

After that you kinda learn not to jiggle stuff when it is running. Plus that valve was weird and known for problems like that.

I did the same thing once when running 3 Lennox furnaces in a small closet/furnace room. I had the fan door of my patient open and the door switch taped closed. Pretty sure the fan was on continuous run.

Started jiggling wires to see if it was a loose connection. Voila it flames out and then starts to fire up again quickly ( I interrupted the ground ). That was bad enough but the other 2 of it's friends were sucking so much combustion air out of the room that it was starved and guess what happens.

FLASHBACK at yours truly.:vs_mad:

Note to self, try not to starve burners for air.

If you want some real horror stories I can give you some hair raising and singing oil burner and gas conversion burner delayed ignition stories.

And yeah we tend to get a bit cocky when we think we know everything or have seen it all. Then tune up time comes around.:vs_laugh:

 

[surferdude2]

Cocky and dangerous is exactly what happens. :biggrin2:

We used to build restaurants and give turn key service to the customer. In order to get health dept' sign off and get the Certificate of Occupancy, it was necessary to have hot water. Since we didn't have utilities released yet, we used a bottle of propane hooked to the water heater to get our health dept. release. The heaters were jetted for NG but so what, big deal... won't hurt them.

Sounds good so far... but on one opening day when the gas company tech did the new equipment checkup and light off, he bled the pipe like he had been trained, to get the air out of it, before attempting to light the pilot. Of course the propane from the pipes settled on the floor and when he struck the match to light the standing pilot, he kissed goodbye to his eyebrows as the entire area lit up about 6" deep with a nice healthy looking blue flame. When he regained his composure, he remarked that he had never seen that happen before.

Since it's a violation of plumbing code to introduce the wrong type of gas into a system, I kept my mouth shut and absorbed the lesson that gravity and propane demonstrated. I made sure the plumber blew the lines out with compressed air after our illegal act was finished from that day forward.

It has been said that good judgment comes from experience and experience comes from bad judgment. Amen to that!