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Megaohmeter.
Megger is actually a brand name.
It's an insulation resistance tester.
You typically test at 2x working voltage to ground.
An open or OL reading is good while a low mega ohm reading is bad.

For example I had a duct heater that would intermittently blow main fuses.
The duct heater resistance was good and no short to ground was found. I disconnected the wires from the contactor and tested every leg and sure enough there was a short which a regular ohm meter wouldn't detect since it didn't have enough voltage for the short to arc across the Bakelite .
It can also be used for predictive failure of compressors with routine megging of the windings.

Ok..,I'll bite,whats the "Megger"?

Originally Posted by Mr Bill

I had one of those Ruud high limits eat my lunch about two weeks ago, the board keep popping fuses, I looked and looked and looked for the problem, finally found a shorted high limit, replace it and all was well. Heck who would have though of checking any limit to ground, I just usually ohm them out.

Whenever I can't find some intermittent problem which causes fuses to pop I pull out the Megger.
You'll be surprised at what I've found to be defective. contactors, airflow switches, transformers, etc.

PS. Love the last line in your sig Br Bill. ΜΟΛΩΝ ΛΑΒΕ

Originally Posted by thump_rrr

Update:
There was a bad connector on the high limit.
Thanks for the help

I had one of those Ruud high limits eat my lunch about two weeks ago, the board keep popping fuses, I looked and looked and looked for the problem, finally found a shorted high limit, replace it and all was well. Heck who would have though of checking any limit to ground, I just usually ohm them out.

Update:
There was a bad connector on the high limit.
Thanks for the help

The blower is running continuously.
I never saw the unit fire.
Ill be going there a bit later.
Thanks ill update once I've gone.

It is. Limit probably stuck open. Tap it and may reset. Replace ASAP but find out why it opened in the first place.

Sent from my HTC VLE_U using Tapatalk 2

I believe its high limit open

Does it cycle the blower ?

Rudd UGPH-10EAMEA Need Help With Flash Codes

I have a client with a Rudd UGPH-10EAMEA gas furnace with HSI.
The thermostat closes and the draft inducer starts. The airflow switch makes but the HSI never glows.
I unplugged the HSI and it never gets 120V

There are 3 LED's on the board:
From left to right there is an amber which I'm assuming is flame which is off.
The center green is flashing 3 times.
The right one is on.

Any help would be appreciated.
A link to Rudd flash codes would be great.