Norcold 1200 Interior light

[Pat & Pete]

Norcold 1200 ... The Interior light doesn't come on .  The old bulb is still good , but , I replaced it anyway . 

There's no power to the bulb at the joint connection for the thermistor / light . The thermistor has power .

I've disconnected all power to the main circuit board for a few minutes . Maybe not enough time for a total reset ? 

It should be noted that the light was working prior to a defrost with the fridge turned off . Restarted the fridge and 

the light doesn't come on .

I'm wondering what might cause that^ ? 

I've searched without finding a single answer .

[Kirk W]

Have you checked the door switch?

[Ray,IN]

2 hours ago, Kirk W said:

Have you checked the door switch?

Great minds think alike. Well, it was just an EWAG for me. My door switches (Norcold has  2 on double door units) get sticky once in a while after the MH has been in storage a few weeks, a few flips with my thumb usually gets the light working again.

I've gotta clean them when I get aroundtuit.

[Pat & Pete]

Door switch ... I thought about pulling them and checking the actual contacts . 

Don't know why I haven't done that yet . I've checked everything else .

I thought that maybe it was something with the main circuit board .

I just tried to pull them , but , they aren't moving . Is there a special method for removing those switches ?

Multiple flicking does nothing . 

[Pat & Pete]

Hmm , No one has ever pulled a light switch from a Norcold fridge ? 

How are they held in place ?

I'd think it a fairly simply affair . 

Maybe I'm not applying enough pressure , but ???

[staffnon]

 

Will this Help??. I don't have that type but maybe this will help.

 

[PDF]

Service Manual - thetford.com

https://www.thetford.com/wp-content/uploads/2015/07/SM_1200-Series_618968C_022707.pdf

Refrigerator Service Manual 1200XX/120X-IMXX Models About this Manual This service manual provides maintenance, diagnostic, and repair information for NORCOLD, INC. model 1200XX/120X-IMXX gas absorption refrigerators. It is a reference tool designed for technicians who are knowledgeable in the theory and operation of gas/

 

www.rvrefrigeratorrepair.com/wp-content/uploads/2016/08/Norcold-Service-1210

see section 6 page 47

 

Interior light:

The interior light is at the top of the fresh food compartment. It

comes on when the refrigerator is ON and the door is open. To

replace the bulb:

1. Remove the DC power supply wires from the power board at

the rear of the refrigerator.

2. Remove the cover [57] by pulling it toward the front of the

refrigerator (See Art00988).

3. Remove the light bulb [58] from the holder [59].

NOTE: Use only a GE#214-2 bulb as the replacement bulb.

This bulb is available at most retail automotive parts

centers.

4. Install the replacement bulb.

5. Install the cover.

6. Connect the DC power supply wires to the power board at

the rear of the refrigerator.

 

Edited January 5, 2020 by staffnon
added info

[Ray,IN]

16 hours ago, Pat & Pete said:

Hmm , No one has ever pulled a light switch from a Norcold fridge ? 

How are they held in place ?

I'd think it a fairly simply affair . 

Maybe I'm not applying enough pressure , but ???

This: https://www.youtube.com/watch?v=AyHG2biVnVw

BTW, there is an old saying, "don't force it, just use a bigger hammer".

Edited January 6, 2020 by Ray,IN

[Pat & Pete]

Thank You guys .

I had the switches out . They gave way reluctantly , likely from being seated for 20 years without any disturbance . 

 Both had continuity in the depressed ( door closed ) position . If that's correct , I'll have to keep looking for another cause .

[Kirk W]

7 hours ago, Pat & Pete said:

Both had continuity in the depressed ( door closed ) position . If that's correct , I'll have to keep looking for another cause .

If the switch is typical, the light should turn on when the switch has 0 ohms and turn off when it goes to very high resistance. While you are working with it, check to see if there is 12V to the switch and if that 12V passes through the switch. It needs to pass the 12V when the door is closed. In most cases that would be with the button depressed.

[oldjohnt]

Pat and Pete, Checking continuity as you did is a good start   "

15 hours ago, Pat & Pete said:

Both had continuity in the depressed ( door closed ) position

One problem is it takes a quality ohm meter to accurately measure very low resistances. Did you test continuity with a cheap continuity checker or an ohm meter??? Also, at low currents the I x R voltage drop wouldn't be very high, while if working under actual operating current to power the bulb, the voltage drop could be high enough to cause an issue.

I believe I'm thinking similar to Kirk in that a person would need to measure the actual voltages UNDER LOAD load to see what voltage is available to the bulb itself. If weak resistive switch contacts (maybe corroded or loose fitting) are causing excessive I x R voltage drop under load, there's less voltage remaining for the bulb itself.

Of course, you need a good solid 12 volts TO the switch itself so there's no excess I x R voltage drop before it even gets to the switch. If you can use a jumper wire to power up the bulb direct from the feed wire (switches input) and it glows fine then but NOT via the switch you have found the problem. A couple jumper wires with alligator clip ends may help test the bulb independent of the (possibly faulty) door switch.  There also has to be a  low resistance ground return path/circuit for the light, look at that also as resistance there can cause the problem even if the switch is perfect ??????????????  

NOTE  ******** do you mean (or shouldn't it be) there's continuity ONLY when the door is OPEN which should cause the light to glow then ????     

NOTE I'm ONLY addressing a potential door switch or resistive ground path/circuit problem, here NOT any other possible problems.   

John T

[Ray,IN]

When the switch is fully-depressed the circuit should be open to turn off the light, no continuity. The thermister is powered separately from the light bulb, as it is always powered any time the refrigerator is turned on.

Have you downloaded the PDF STAFFNON linked? I think it has a wiring diagram.

[rickeieio]

Wouldn't a jumper wire across the switch be a lot simpler, and easier, that fiddling around with an ohm meter?  

[Pat & Pete]

It's been a week , but , I haven't abandoned this , yet . ;)

 Rain day here tomorrow , so , I plan to get after this problem while trapped inside anyway . 

I'll let you know just what I come up with , good or bad . 

Thanks , again . :)

[Pat & Pete]

Finally got around to messing with the fridge . 

Disconnected all power for close to an hour and connected the board positive to ground to try evacuating any leftover power in any circuits . 

I even disconnected the eyebrow board to check for any corrosion . None to be found and connections seem clean and tight .

Checked voltages : almost 13 on the twelve volt input and 126 on the 120 input . 

Reconnected everything as it should be and restarted the fridge . 

Still no light .

I'm thinking there must be a bad something on one of the boards , but ??? 

Everything else works as it should . 

Maybe I should install a couple magnetic switches and rewire the light separate from the main board .

That would likely be a lot cheaper than a new board .

[Kirk W]

13 hours ago, Pat & Pete said:

Still no light .

We are assuming that you have tried a new light bulb? I know that sounds simplistic but also know someone who spent hours troubleshooting a light failure on an appliance and then paid to have a tech discover one burned out. 

[Wrknrvr]

  I would start back tracking 12 vac power from the bulb positive contact and the ground at the same time . Use a jumper wire attacked to the gas line on the range . That should be a good ground. Use that to test to see if there is power to the the positive side of the light when light should be on. if there is then attach that ground wire to the ground side to see if the light works.

  If need be follow every connection back to the 12vdc power source.

 

 Last week a customer brought me a Suburban furnace that would not work. He installed a Dinosaur board and it would not turn the fan on. I repaired a bad solder joint on his old power board. It did not work. So with putting 12vdc to  the fan motor it worked. So. I traced 12vdc through the system. It had 12vdc everywhere it was suppose to be. 

 

 Pulled the 12vdc switch that is on the side of the furnace and put in a 12vdc fuse. Ddddmmmm thing worked, 

 yes that switch passed 12vdc through the switch to the board, but did not apparently pass enough amperage to operate the control board.

 

  Just thinking,   Vern

[oldjohnt]

14 hours ago, Pat & Pete said:

 

I'm thinking there must be a bad something on one of the boards , but ??? 

Pat & Pete, Thanks for the update.

I cant say if the board is what supplies voltage to the switch and light orrrrrrrrrrr if its 12 volt source is total independent of the boards function???????? If the board is the source then sure it has to work...……..

Regardless where the 12 volt source feed comes from, there MUST be 12 volts getting TO the switches INPUT and if the door is open the switch closes and applies voltage to the light bulb which (if other terminal has a good ground) if good ????? will light.

Insure theres voltage TO the switches INPUT,,,,,,,,,When the door opens the switch closes with continuity so 12 volts gets to the bulb,,,,,,,,,,,,,,,,The bulb is good and continuous,,,,,,,,,,,,,,,,,theres a good ground to the bulbs orther side.

A simple ohm meter (test for continuity when door open or no continuity when closed) can check the switch and a simple volt meter can test for good voltage to the switches input and insure a good ground.

That switch needs 12 volts PLUS a good ground path,,,,,,,,,,switch needs to open and close,,,,,,,,,,,bulb must be good...

John T

[Pat & Pete]

On 1/7/2020 at 9:21 PM, Kirk W said:

If the switch is typical, the light should turn on when the switch has 0 ohms and turn off when it goes to very high resistance. While you are working with it, check to see if there is 12V to the switch and if that 12V passes through the switch. It needs to pass the 12V when the door is closed. In most cases that would be with the button depressed.

The switches pass 13.6 volts with the doors closed ( switches depressed ) and nothing when the door(s) are open .

And , the bulb is new and tested . Works fine . 

On 1/8/2020 at 6:30 AM, oldjohnt said:

Pat and Pete, Checking continuity as you did is a good start   "

NOTE  ******** do you mean (or shouldn't it be) there's continuity ONLY when the door is OPEN which should cause the light to glow then ????     

NOTE I'm ONLY addressing a potential door switch or resistive ground path/circuit problem, here NOT any other possible problems.   

John T

The switches are open when the door(s) is/are open . 

That leads me to think that the light is acting as a ground path for an unknown , at this point , circuit .

And , Yes , I'm using a good Multi-meter .  

On 1/9/2020 at 10:52 AM, Ray,IN said:

When the switch is fully-depressed the circuit should be open to turn off the light, no continuity. The thermister is powered separately from the light bulb, as it is always powered any time the refrigerator is turned on.

Have you downloaded the PDF STAFFNON linked? I think it has a wiring diagram.

The switches are opposite that^ . They are conductive only when they are depressed ( door(s) closed ) .

And , Yes , I have the manual . It does not have a full wiring diagram . Only a pictorial and a basic wire path diagram .

On 1/9/2020 at 1:10 PM, rickeieio said:

Wouldn't a jumper wire across the switch be a lot simpler, and easier, that fiddling around with an ohm meter?  

Once the meter is set correctly , it's just as simple as a jumper wire and it provides details as to what and how much .

 

 

[Ray,IN]

4 hours ago, Pat & Pete said:

The switches pass 13.6 volts with the doors closed ( switches depressed ) and nothing when the door(s) are open .

And , the bulb is new and tested . Works fine . 

The switches are open when the door(s) is/are open . 

That leads me to think that the light is acting as a ground path for an unknown , at this point , circuit .

And , Yes , I'm using a good Multi-meter .  

The switches are opposite that^ . They are conductive only when they are depressed ( door(s) closed ) .

And , Yes , I have the manual . It does not have a full wiring diagram . Only a pictorial and a basic wire path diagram .

Once the meter is set correctly , it's just as simple as a jumper wire and it provides details as to what and how much .

 

 

You are correct, sorry about that, I was backasswards.

[Kirk W]

12 hours ago, Pat & Pete said:

The switches pass 13.6 volts with the doors closed ( switches depressed ) and nothing when the door(s) are open .

In this case then the switch is supplying a ground, rather than power. Not too unusual in 12V-dc circuits. Did you try checking from the switch to ground to see if the ground connection is good? It sounds like what you have is a bulb that has 12V supplied all of the time and the switch is in the return side and when depressed it then closes to supply a ground to the already energized light bulb. You could use a jumper wire from a known good ground source to either side of the 12V side of the switch to see if the light then turns on. 

[Pat & Pete]

19 hours ago, Ray,IN said:

You are correct, sorry about that, I was backasswards.

No worries . Been there and done that . More than I'll admit . LOL

 

10 hours ago, Kirk W said:

In this case then the switch is supplying a ground, rather than power. Not too unusual in 12V-dc circuits. Did you try checking from the switch to ground to see if the ground connection is good? It sounds like what you have is a bulb that has 12V supplied all of the time and the switch is in the return side and when depressed it then closes to supply a ground to the already energized light bulb. You could use a jumper wire from a known good ground source to either side of the 12V side of the switch to see if the light then turns on. 

I know the switch ground point at the main board is good as I'm using it to ground an auxiliary cooling fan . 

But , that doesn't prove the rest of the wiring is good  . I'll have to try your suggestion of a known good ground point ...

As to how the light is used in the circuit , like I said : 'That leads me to think that the light is acting as a ( alternate ) ground path for an unknown , at this point , circuit .'

Edited January 21, 2020 by Pat & Pete
clarification

[oldjohnt]

   If you think about it, regarding ONLY the light itself (not any board control or electronics) what you have is a simple series DC circuit (Battery +,,,,,,,switch,,,,,,,,,light,,,,,,,,,,battery - orrrrrrrrrrr Battery - ,,,,,switch,,,,,,,,,,,light,,,,,,,,,battery +) and it DOES NOT MATTER if you switch/supply  the - ground circuit orrrrrrrrrr  switch/supply the + 12 volt circuit, switching off EITHER side,  + or -   OPENS the circuit so the light cant glow.

 If there are two wires to the switch and light, to work you need 12 VDC +,,,,,,,,12 VDC -,,,,,,,,,,light,,,, and an On/Off switch (regardless if on - or + side) 

What seems confusing is intuitively if you OPEN the door, the switch would CLOSE and the light gets 12 volts and glows. If the door CLOSES the switch OPENS and the light goes off BUT THAT SEEMS  NOT THE CASE ?????????

Are there or are there not two wires to the light and switch that have 12 volts across them ?????????? 

If NOT the light cant glow regardless of switch operation. There MUST be + and - 12 Volts on two feed wires !!!!!!!!! if theres no + orrrrrrrrr no - ,  NO light.

Try substitute/jump a know good - ground...……...If that's NOT the problem, try substitute/jump a known good +

A simple test light or volt meter and a continuity tester or ohm meter should help identify the problem

NOTE again this concerns ONLY the light itself and nottttttttttt any board function or if a ground signal is sent to the board via the light circuit or any other electronic type of system and not having the circuit diagram I JUST DONT KNOW HOW THIS ALL WORKS so no warranty...…. 

Best wishes let us know what happens

John T  Live from Avon Park Florida

[Wrknrvr]

 Looking at the diagram for that fridge it has two green wires or atleast coded that way. for the switch. So I take that as it is switching the ground. Some things today they switch the ground side instead of the hot side. Now if the ground is not connected then it actually is hot. So one of those wires to the switch should test for power if metered to the center of the range. The rage is grounded as it is hooked to the copper gas line. It is usually sorta close to the fridge.

 The diagram is at Bryant’s rv.. I am working today so that puts a time limit helping.i

i am in the  middle of a bucket list  project I started 40 years ago.

 

  Yep it has been 40 years in the making for that bucketlist .

 

its antique before it is finished.

 

  Working on retirement,    Vern 

 

  

[staffnon]

rvrefrigeratorrepair.com/wp-content/uploads/2016/08/Norcold-Service-N61x-N81x.pdf 

Page 34 and Page19 Fig 21

Lamp Assembly The operation of the fresh food compartment 12 Vdc lamp is controlled by a magnet activated reed relay switch. The switch is in the optical control circuit board and the magnet is permanently mounted on the underside of the door's top trim piece.
Leaving the door ajar or open for more than two minutes causes the controls to display a "d" or "dr" fault code (depending on unit model). Closing the door turns off the light and clear the "d" or "dr" fault indicator from the display. However, the fault code will be stored in the diagnostic mode nonvolatile memory. For "d"/"dr" troubleshooting procedures. See page 19. As shown in Figure 21, the light assembly harness and thermistor share the same connector. Remove the light cover to access the connector.
 

You have checked the magnet??. How do you check the light assembly with meter, if the switch is removed away from the magnet??

And what are the error codes displayed?? The switch is in the optical control circuit board

ALSO what has NORCOLD?? told you inquiring minds want to know!! 

Edited January 22, 2020 by staffnon
added page #'s

[oldjohnt]

29 minutes ago, staffnon said:

 

You have checked the magnet??. How do you check the light assembly with meter, if the switch is removed away from the magnet??

And what are the error codes displayed?? The switch is in the optical control circuit board

ALSO what has NORCOLD?? told you inquiring minds want to know!! 

Yo Staff,,,,GREAT information for the original poster (when all else fails read the instructions lol) ...….From that it appears a magnetic activated reed relay signal to the circuit board is what controls the actual On/Off light switching. That's NOT the same as a mechanical door open/close activated light switch I discussed above, sorry about that. Troubleshooting therefore is a tad bit more complicated but still possible especially now that the circuit is understood.  If its the type of magnetic activated relay I've seen there's not much room for error as far as the magnets location and spacing.    I would wonder Is the magnet still there and in place ???? If not or incorrectly located that's bad...So is it a mechanical magnet problem orrrrrrrrrrrrrr a control board failure ??? Hmmmmmmmmmmm

Getting complicated but fun and educational regardless...

An ever curious John T