3 way fridge not working on mains

[Tony Brooks]

32 minutes ago, MtB said:

 

Zero Ohms tells us the element resistance is WAY too low. I'd expect a value in the order of 1,000 Ohms. The element might have melted and connected with the metal case surrounding it, but whaever has happened, a resistance of zero Ohms will blow the fuse in the three pin mains plug. 

 

 

 

I have just got the AC power rating for a Dometic absorption fridge (135W) and worked through the online calculator to get expected resistance of the element. It came out at 400 ohms or there about. But that would be hot resistance, the cold resistance should be a lot lower because the element will have a positive temperature  coefficient. I accept probably not zero.

15 minutes ago, blackrose said:

With those two brown cable terminals connected to their respective connection points?

 

Edit. With the brown cables connected and measured at those terminals I'm still getting nothing on the ohms setting on my multimeter while twiddling the knob. 

 

When you say nothing exactly, what does it show and what when you hold the two cable probes tightly together. It is not common for an ohmmeter to show zero ohms unless you are measuring a short circuit, so I am suspecting your meter.

Edited August 30, 2021 by Tony Brooks

[Tracy D'arth]

7 minutes ago, blackrose said:

With those two brown cable terminals connected to their respective connection points?

 

Edit. With the brown cables connected and measured at those terminals I'm still getting nothing on the ohms setting on my multimeter while twiddling the knob. 

You obviously do not know how to use and read the meter or how an electrical circuit operates. This is going to be difficult.  If the resistance is very low the meter on ohms will read a low value. If the heater element is open circuit, burnt out, it will either read a very high or infinity value usually a "1" on the meter left hand side. That does not mean 1 ohm.

 

I am thinking that this is not a mains element? but the 12v one? If so how does the fridge work on mains?

 

The thermostat may click as you turn it both ways but you need to put the meter across the 2 terminals on the thermostat itself to see if it opens and closes when it clicks.

[blackrose]

17 minutes ago, Tony Brooks said:

 

 

When you say nothing exactly, what does it show and what when you hold the two cable probes tightly together. It is not common for an ohmmeter to show zero ohms unless you are measuring a short circuit, so I am suspecting your meter.

 

The meter is showing 0.L ohms. 

 

With the probes held together I'm getting between 3.8 - 4.6 ohms.

Edited August 30, 2021 by blackrose

[Tracy D'arth]

1 minute ago, blackrose said:

 

The meter is showing 0.L ohms. 

 

With the probes held together I'm getting about 3.8 ohms.

That is not logical unless the reading of 0.1 on your meter is really infinity, i.e. open circuit in which case I think it is really showing  -1  not  .1

[MtB]

1 minute ago, Tracy D'arth said:

That is not logical unless the reading of 0.1 on your meter is really infinity, i.e. open circuit in which case I think it is really showing  -1  not  .1

 

These weird and unreliable meter readings on a DVM sometimes turn out to be a flat battery. 

[blackrose]

2 minutes ago, Tracy D'arth said:

That is not logical unless the reading of 0.1 on your meter is really infinity, i.e. open circuit in which case I think it is really showing  -1  not  .1

 

I didn't say 0.1 I said 0.L whatever that means? Unless that means 0.1?

1 minute ago, MtB said:

 

These weird and unreliable meter readings on a DVM sometimes turn out to be a flat battery. 

 

I'll change the battery and try again...

[Tracy D'arth]

Just now, blackrose said:

 

I didn't say 0.1 I said 0.L whatever that means? Unless that means 0.1?

The resistance reading cannot be lower connected to the wires than it is with the probes shorted together. As I said, not logical, in fact impossible. Your meter is not correct, check the battery first.

[frangar]

Without knowing the meter could O.L stand for “overload” eg out of range therefore an infinity reading (open circuit) rather than zero ohms?? 

[MtB]

1 minute ago, frangar said:

Without knowing the meter could O.L stand for “overload” eg out of range therefore an infinity reading (open circuit) rather than zero ohms?? 

 

Time for the OP to read the manual that came with the meter to find out.

 

O.L if it means infinity would display all the time, not just when the test probes are applied to the pair of terminals. 

 

O.L might be the warning display if the meter is set to measure resistance and the probes are applied to terminals still with a voltage across them. 

[blackrose]

6 minutes ago, frangar said:

Without knowing the meter could O.L stand for “overload” eg out of range therefore an infinity reading (open circuit) rather than zero ohms?? 

 

It's a Fluke meter. Looking on the net it says "Infinite resistance (open circuit) is read as OL on the Fluke meter display and means the resistance is greater than the meter can measure"

 

I'm getting the same readings with a fresh 9v battery fitted in the meter.

Edited August 30, 2021 by blackrose

[frangar]

4 minutes ago, MtB said:

 

Time for the OP to read the manual that came with the meter to find out.

 

O.L if it means infinity would display all the time, not just when the test probes are applied to the pair of terminals. 

 

O.L might be the warning display if the meter is set to measure resistance and the probes are applied to terminals still with a voltage across them. 

Indeed. There are a few variables and who knows how the mind of the Chinese design engineer works! As you say best to check the manual…or just use a simple continuity tester with a led/battery etc. Even with the resistance of a heating element it should light up with a complete circuit. 
 

edit to add maybe an American design engineer if it’s a fluke! 

Edited August 30, 2021 by frangar

[MtB]

2 minutes ago, frangar said:

There are a few variables and who knows how the mind of the Chinese design engineer works!

 

Plagiaristically, typically!

[frangar]

4 minutes ago, blackrose said:

 

It's a Fluke meter. Looking on the net it says "Infinite resistance (open circuit) is read as OL on the Fluke meter display and means the resistance is greater than the meter can measure"

 

I'm getting the same readings with a fresh 9v battery fitted in the meter.

I’ve just checked on my Fluke 177 set to ohms. It says OL when the probes are in free air as you would expect. And a reading when they are on a bit of cable. I’d suggest your element is open circuit. Have you tried the continuity buzzer on the element? 

[blackrose]

So wouldn't a continuity test have been the first thing to do? As I mentioned earlier I did a continuity test and didn't get any. 

 

Since there was no continuity is it surprising that I'm getting no resistance reading? I'm puzzled as to why everyone was focused on resistance, but I'm obviously missing something.

 

 

5 minutes ago, frangar said:

I’ve just checked on my Fluke 177 set to ohms. It says OL when the probes are in free air as you would expect. And a reading when they are on a bit of cable. I’d suggest your element is open circuit. Have you tried the continuity buzzer on the element? 

 

Yes! See my earlier post.

 

Anyway, can we say the element is dead, yes?

Edited August 30, 2021 by blackrose

[frangar]

7 minutes ago, blackrose said:

So wouldn't a continuity test have been the first thing to do? As I mentioned earlier I did a continuity test and didn't get any. 

 

Since there was no continuity is it surprising that I'm getting no resistance reading? I'm puzzled as to why everyone was focused on resistance, but I'm obviously missing something.

 

 

 

Yes! See my earlier post.

 

Anyway, can we say the element is dead, yes?

To be fair if there was a high measurable resistance then the continuity tester might not have worked. But using both together I think we can assume that its pointing towards the heating element being duff unless someone who has experience of these knows a good reason why it might give those readings but work fine....

[blackrose]

6 minutes ago, frangar said:

To be fair if there was a high measurable resistance then the continuity tester might not have worked. But using both together I think we can assume that its pointing towards the heating element being duff unless someone who has experience of these knows a good reason why it might give those readings but work fine....

 

Ok thanks

[Tony Brooks]

12 minutes ago, blackrose said:

So wouldn't a continuity test have been the first thing to do? As I mentioned earlier I did a continuity test and didn't get any. 

 

Since there was no continuity is it surprising that I'm getting no resistance reading? I'm puzzled as to why everyone was focused on resistance, but I'm obviously missing something.

 

 

Yes, if your meter has a continuity reading and in some cases it's on the diode test or even the Ohms setting. Until you told us you had a Fluke we had no idea what you had, and a properly conducted resistance test will tell us all we need to know.

42 minutes ago, blackrose said:

 

The meter is showing 0.L ohms. 

 

With the probes held together I'm getting between 3.8 - 4.6 ohms.

 

I would not expect that on a Fluke - possibly on a Uni type meter. I suspect loose or dirty connections where the cables push into the meter or a frractured probe cable.

[frangar]

15 minutes ago, Tony Brooks said:

 

I would not expect that on a Fluke - possibly on a Uni type meter. I suspect loose or dirty connections where the cables push into the meter or a frractured probe cable.

My Fluke 177 with an in date calibration cert gives a reading of 0.2 ohms when the probes are touched using the longer set of fluke test leads I have. It does take a second or so to stabilise at that reading when on the auto range setting. 

[Tony Brooks]

4 minutes ago, frangar said:

My Fluke 177 with an in date calibration cert gives a reading of 0.2 ohms when the probes are touched using the longer set of fluke test leads I have. It does take a second or so to stabilise at that reading when on the auto range setting. 

 

That is fairly typical across  a lot of makes but not 3 to 4 ohms.

[blackrose]

1 hour ago, Tony Brooks said:

 

I would not expect that on a Fluke - possibly on a Uni type meter. I suspect loose or dirty connections where the cables push into the meter or a frractured probe cable.

 

I've tested with two different sets of cables and the connections are clean and tight. The second set of cables is showing a resistance of 0 so maybe it is the cables.

 

The meter works perfectly when checking various voltages elsewhere with both sets of cables. 

Edited August 30, 2021 by blackrose

[frangar]

Just now, blackrose said:

 

I've tested with two different sets of cables and the connections are clean and tight. How could the cables be fractured if I'm getting readings with the probes held together? The meter works perfectly when checking various voltages elsewhere so I'm sure the probe cables and connections are fine.

The beauty of a Fluke is its worth getting it calibrated unlike cheaper meters. Nothing quite so annoying as faulty test equipment....got that t shirt a few times over the years...mainly using other peoples test kit! It might be that its just the Ohm range thats out of kilter for some reason.

[blackrose]

With the second set of test leads in still getting the 0L reading. They're brand new leads.

 

Maybe the meter is out of calibration.

 

Still no continuity with the second set of test leads. Both sets of test leads buzz on the continuity setting when held together. 

Edited August 30, 2021 by blackrose

[blackrose]

10 minutes ago, frangar said:

The beauty of a Fluke is its worth getting it calibrated unlike cheaper meters. Nothing quite so annoying as faulty test equipment....got that t shirt a few times over the years...mainly using other peoples test kit! It might be that its just the Ohm range thats out of kilter for some reason.

 

Where did you get yours calibrated?

[frangar]

1 minute ago, blackrose said:

 

Where did you get yours calibrated?

Mine was new last year so I got it done by the supplier before they sent it out....If you have a google for Multimeter calibration you should find someone..RS do it but they aren't cheap and since I had a courier bounce a PAT tester I've always tried to take/collect it in person so someone local is better....you dont always need it to UKAS standard which can be more expensive...just the in house is good enough unless you need to prove it for any reason. 

[Tony Brooks]

51 minutes ago, blackrose said:

With the second set of test leads in still getting the 0L reading. They're brand new leads.

 

Maybe the meter is out of calibration.

 

Still no continuity with the second set of test leads. Both sets of test leads buzz on the continuity setting when held together. 

 

It is not 0L, it is OL and that stands for overload that means the meter is not capable of  taking a reading on that setting. If it is not a self ranging meter one would step up through the Ohms ranges until you got a reading or not, You might get one on the K Ohm or M Ohm ranges bit you will still get OL if it's open circuit. Many meters will not show OL but put what looks like a 1 but is supposed to be an I on the left of the window. The I stands for infinity.

 

I am sure your meter is accurate enough for boat use.