Back to basics.

[Grizzly]

The old adage.
If in doubt go back to basics! Still applies.
How many when en-route to a break down have, in their mind at least got the errant chiller etc stripped to almost a rebuild state?
And when you arrive and take stock it's a 5Amp control fuse! That actually happened to me once after 2 hrs of driving to site.

Or the chillers that randomly tripped out on their flow switches.
To eventually discover that the site operative that monitored the glycol levels from an opening within the buffer tank. Had previously lost the plastic cup off the end of his stick!
This had sunk and was periodically being drawn into the water flow outlet, small end first.
Compounding the circulating pumps pressure as the more they sucked the more the cup stuck.
That one took a long time to find.

One of the best is from years ago though. Where the newly qualified plumber on this site wired up a boiler temporally to a 13amp 3 pin plug and socket.
On failing to be able to prove the boiler. He calls his boss, who together with another Engineer spend all afternoon changing fan sensors, circuit boards etc.
When at the end of a long afternoon they actually check the incoming supply.

Yep the young guy had wired up the live and neutral the wrong way around in the plug.
Should of checked the basics.
Grizzly

[monkey spanners]

I spent ages once trying to find out why an air blower wouldn't put out enough air to bubble the water in an ice builder, cleaned the air filter, checked the pressure relief valve, made an adaptor to use fridge gauge to measure output pressure, even went as far as stripping the head off it to check the rubber diaphragm that served as a piston. It was some time after this i found that a rat had chewed through the plastic airline as it passed through a hollow block wall, the thing was so noisey you couldn't hear the air leak when it was running

Jon

[r.bartlett]

I remember once spending ages and ages over a new evap fan I fitted into a cold room. whilst Leaning with my shoulder against the door keeping it ajar for more light I couldn't for the life of me work out what I'd done wrong then it suddenly dawned on me: I looked up and yep> the bloody thing was wired through a door switch !

[Grizzly]

R.B.
Your post made me smile and think of the time I was sent to repair a non working locked in alarm within a Dawson Rental's container.
Sure enough the alarm did not operate when it's Panic Button was pressed. At the same time I noticed that the GLS Lamp was not working.
So off I toddled to the nearest superstore purchased a new Bayonet cap Bulb, fitted it and switched on.
The container was now bathed in light, guess what the locked in alarm now worked!
Someone had wired up the alarm from the switched side of the light. Not the feed side.
Because the bulb had blown no-one bothered to switch it on... = Alarm off!
Grizzly

[Magoo]

Hi Grizzly.
Had to smile at all the above, I try and enstill in the young techs not to fix the problem while driving to site, but make a decision based on all info once on site. Service gauges, ammeter. Touch it feel it, everything.
In particular the message from service controllers/ despatchers really annoy me, things like "sounds like its short of gas " senario. What, they have telepathic vision, after speaking to a clients incall.
magoo

[mikeref]

Grizzly, top marks for description of events that circulate in the grey matter!! When on the way to jobs that have significant dollar value, i can't help but mentally strip the equipment to pieces looking for weakness, followed by, do i have the parts on board, followed by, where would be the nearest location to get them. On site, there is several plans of attack ready to be put into action, the customer is already in your ear just as the electrical board is opened.... Whats the problem... coldroom off on defrost. The room does this every day at this time. Why the panic now??