The operation light on my MEX water heater Type 3700 3C doesn't come on (was working fine yesterday) and as a result there's no hot water. Any ideas what I should do ?

Thanks in advance.

My first steps would be reset button, check fuse, then call electrician. And then I would save for new powerful heater before winter!

My advice: use the cold water.  You will gain some acceptance of life.

Check the breaker in the fusebox.

Low water pressure could cause that.  Heaters require a minimum level of water pressure or they will not turn on.

 

If it is an electrical problem, you may get it running by one of the above mentioned ways but best have an electrician check things to find out why the problem occured and fix it. 

45 minutes ago, beau thai said:

then call electrician

That would probably be your best bet if you've just checked the breaker/use and if there is a reset button which you can actually press....... and nothing has worked!

 

Usually in these devices there is a pressure switch which is activated by the water flow and "turns on" the element for the heating. In addition, and depending upon the type of internals your shower heater has, there will either be a thermal cutout attached to the metal cylinder, if indeed it is metal, or will be in the line of the power supply to the element.

 

These are easily checked by an electrician, and of course it could always be the element which has decided to give up the ghost!

 

Whatever, after you've done what I suggested in my first paragraph, leave the rest to an experienced electrician.

the GFCI do wear out.  

Water heaters have several weaknesses.
Is your water pressure now reduced?
Is there an inlet filter on the heater that is now clogged?
There maybe an over-temp trip that needs to be reset, usually on top of the heater pot (remove power before opening the box.)
I don't know your unit, but if there is no sign of life at all, it is usually either low water pressure (filter) or control circuit inhibition because of a fault or condition. The first test I do unless I have a meter handy is short the water flow sensor switch, if it is a simple switch.

Finding an electrician that will look at it properly can be a problem. The typical village 'electrician' usually just says 'buy new'. I've seen over temp cut-outs and blocked water inlet filters dismissed as 'no good - buy new'.

What exactly do you mean when you say:

Quote

The operation light on my MEX water heater Type 3700 3C doesn't come on

I have the same model (only the 5100W version), and on mine the light is always on. When not in operation the light is green, and it changes to blue when the unit starts heating water. If you have no light at all, I would suggest that there is a problem with power to the heater, or that the ELCB has been triggered (try pressing the reset button). If the green light is on but doesn't change to blue, then maybe you have a water flow problem (although mine works with a very limited water flow).

 

Sophon

 

That one has a low voltage ELCB built in... so it makes me wonder that now it is hot as Hell again, and you are running ac and fans.. and getting a voltage drop, or even a neighborhood wide low voltage situation.  The last few days in BKK have been major league hot.  If you have small meter 5/15 service, you really need to watch the load.  Sure you can have ac and hot shower.. but you gotta watch simulateous usage. 

Post removed.  Phone numbers, email addresses and other personal information is not allowed on the open forum.  

 

Thanks to all of you for your suggestions.

Our condo technician came by and removed the lid of the heater and found a broken fue inside.

After replacing it and turning the main breaker back on, the tiny black cylinder-shaped thing next to the fuse released a ray of smoke and that was the end of the operation.

Bought the same heater at Home Pro yesterday (4500 Baht) and the technician from them will come over and change the heater tomorrow without any further cost.

Hope that will solve the problem. Thanks again

10 minutes ago, Beng said:

After replacing it and turning the main breaker back on, the tiny black cylinder-shaped thing next to the fuse released a ray of smoke and that was the end of the operation.

The magic smoke has escaped leading to death of the appliance.

25 minutes ago, Beng said:

Bought the same heater at Home Pro yesterday (4500 Baht)

Perhaps you had 10 years good service (?) but suspect I would not be buying the same model after one died.  But at least it should be an easy install and you already know how to use.

Living the dream with a 2 wire HWH installation.... 

On 10/29/2019 at 4:22 PM, sometimewoodworker said:

On 10/29/2019 at 4:10 PM, Beng said:

After replacing it and turning the main breaker back on, the tiny black cylinder-shaped thing next to the fuse released a ray of smoke and that was the end of the operation.

The magic smoke has escaped leading to death of the appliance.

Chances are the condo "technician" replaced the blown fuse with a larger amperage fuse (they all look the same to the average condo technician anyway) and the "tiny black cylinder-shaped thing next to the fuse" that was already breaking down under load gave up the ghost. Smart move to just replace it completely. Touch wood, both my Panasonic home shower units are now over 12 years old and still working great... when the moobahn mains voltage is high enough!