It was last night but, fixed a bunch of trouble codes on a fire panel at our neighbor hotel.
Several days ago something happened and they lost all the smoke detectors, pull stations, and anything else that is addressed and connected to the same lines.
They call a tech out for repair. They apparently did the usual, swapped the batteries (not sure why that would be the solution) reboot the system. Same issue. Said it was the motherboard and needed to order one and would be back later to install it.
Fast forward a few days, I get called over to help diagnosis a warm walk-in freezer and I noticed the trouble light on the fire panel. Find out it has been like that for several days with no working fire system and guests occupying the hotel.
I told the maintenance guy that I call BS on the "Techs" diagnosis after hearing how he cam to the conclusion.
Came back the next day and did a simple test, where I disconnected the main line from the motherboard and hooked one smoke detector directly to it. Sure enough it turned on and reported it operational (with all the others still off line). This right there prooved it was not the motherboard. Took me all of two minutes to figure that out.
Took my meter an tested continuity on the main smoke detector line. Dead short. Followed the line from detector to detector disconnecting the line that is shorted out an reconnecting the good lines. Ended up with the last device being a manual pull station in the area under renovation. Go figure.
Three hours of work and we had the rest of the building back on line with just one pull station in the construction area. No expensive motherboard replacement.
Makes me angry when these techs that are supposed to know their equipment fail at basic troubleshooting. Maybe they don't make enough money from telling their customers the is a short on the line and fix that and everything is good. Instead they bill them for batteries, motherboard, expansion cards, reprogramming the new boards, and then finding and fixing the short when the new motherboard shows the exact same codes.
I don't know if the are just that stupid or they are being trained to think like that. Had a similar situation at my hotel on my day off. Instead of calling me they call a tech out and he replaced a few smoke detectors and said it must be the motherboard. When I showed up I put a stop to it. Told them those "bad detectors" you replaced are also powered by an aux. 24v line. The code on the fire panel said loss of 24v line. That same power also ran the door hold magnets. Sure enough the same construction crew had removed a magnet and the wires where shorting out on the door.
Boils my blood when they do that. Anyways, felt good to get that hotel figured out and potentially save a lot of lives if there happen to be a fire in the building. Murphy's law says there will be