Norcold SCQT repair?

[ABJ87]

Does anybody have any tips for troubleshooting a Norcold SCQT icebox conversion kit?

I can't get the unit to turn on... I it has power, both 12v and 120v.

With it being a less than 3 year old unit I contacted Norcold, but they are less than helpful...

Any suggestions were to start?

Thanks!

[Richard Kollmann]

There are over twenty different electrical drawings on Norcold units. You report unit will not run either on AC or DC.
For unit not to run on either power source it means an item common to both is the cause like:
· The master transformer that has several coils inside. This compressor operates on 22 or 26 volts of AC current or 22 to 26 volts pulsating DC current. This transformer steps down AC voltage or Increases DC voltage. From my experiences when transformer fails you will smell burnt electrical in the box. A small inverter/converter on the DC side produces 60 cycles to excite the vibrating magnet actual motion inside compressor. There is a relay switch inside the electronic box that removes DC power and connects AC power. This relay is activated when ever AC power is available. This is a double through relay if AC relay contacts are faulty unit will not run on AC or DC if AC power is available at refrigerator Have you tried to run unit on DC with AC power turned OFF?
· Faulty Thermostat
· Some Norcold modules have two small circuit breakers look for a small button on thermostat
· There is a small thermo switch on condenser coil see if it is still intact and not overheated.
· This compressor will hum when running. There are two wires connected to compressor the ground wire is attached with a screw the power wire is a single plug. Warning DO NOT DISCONNECT POWER WIRE WITH DC POWER CONNECTED TO REFRIGERATOR as it can damage small DC converter.

[ABJ87]

thanks!!!!!

This will give me somewhere to start!

[happyendings]

I just installed a Norcold SCQT 4407 icebox conversion unit and have similar problems. The unit runs fine on 120 VAC but will not run on 12 VDC. With 12 VDC applied, the fuse blows on the 12 volt line when AC power is removed. Any thoughts?

[Richard Kollmann]

Are you sure the polarity of power wire and ground are Correct?

If fuse that blows is correct size and is inline near power source disconnect 12 volt wires you connected to unit and replace fuse. If fuse blows again then problem is in boat's wiring after fuse.

When you have eliminated polarity and boat wiring then trouble is in side electronic box part of system itself.

[happyendings]

@ Richard Kollman: Assuming that the red wire coming out of the unit is positive and the black wire is negative, then yes the wiring is correct. I rang it out again just to be sure. This is a shot in the dark, but maybe the voltage sensitive relay is hanging up in the AC position? Do you know where I can locate the (many) drawings for the unit that you mentioned in a previous post? I will run the unit on AC until I have more time to troubleshoot. Using only the AC power inlet, it draws about 7 amps DC running on the inverter which will be fine as I motor down the ICW next week. As always, thank you for your service to our community RK.

[Richard Kollmann]

I do not see how change over relay could be the problem. Will unit still blow fuse if new fuse is installed in 12 volt wire while unit is running on AC and the DC breaker is turned on? If fuse blows in this condition it is not the 12 volt power transformer winding that is shorted.
Have you tried turning off AC power? Without AC power relay can not affect DC side of system.

Norcold will email you a drawing for that model if you contact them with Model and serial number of unit. But getting inside to see the DC complex pulse voltage electronic is a difficult chore.

That unit normally draws 3 amps on DC power and double that when running off an inverter my advice is if you do not find a wiring problem keep running unit on an inverter. The only way I would attempt to remove electronic box is if it could be done without disconnecting refrigerant lines.

[mashenden]

I too just recieved a SCQT 4407 unit that needs some repairs. Mine has damaged/missing lines, missing thermostat, as well as a good compressor unit and a good evaporator. Before I buy a replacement thermostat, I would like to test my repairs.

Does anyone know what I should do to the 5 wires (red, black, orange, yellow, brown) that normally plug to the thermostat so that I can get the unit running? I have a thermostat to an older unit but it only has 4 wires - no orange.

[mashenden]

Originally Posted by mashenden

... Does anyone know what I should do to the 5 wires (red, black, orange, yellow, brown) that normally plug to the thermostat so that I can get the unit running? I have a thermostat to an older unit but it only has 4 wires - no orange.

I figure the old thermostat would work but don't know for sure. HELP!! What does the orange wire that goes to the thermostat on a SCQT 4407 do?

[mashenden]

Richard Kollmann, do you have access to wiring diagrams for the Norcold SCQT4407? I was hoping you could comment on what the wires do, or minimally, what needs to be done to test the unit before buying a thermostat/controller. Thank you in advance.

[Richard Kollmann]

Sorry, I can not help with Norcold wiring I did have 21 different wiring systems for them but trashed them when I closed my shop. If Norcold will not E mail you a drawing that matches your serial number and model you may never find the one you need. Twelve years ago Electric Boat refrigeration did repair the Norcold electronics component boxes try them for a drawing if Norcold will not help you.

[mashenden]

Originally Posted by Richard Kollmann

Sorry, I can not help with Norcold wiring I did have 21 different wiring systems for them but trashed them when I closed my shop. If Norcold will not E mail you a drawing that matches your serial number and model you may never find the one you need...

Darn. Thank you anyways

One thing I have learned about Norcold is that their customer support is one of the worst I have ever experienced. Calling them is akin to talking to a brick wall . How they think they can charge that much for a system, not even provide a service port to top off the charge, and support it as though it is disposable is beyond me .

I'm convinced the marginal cost savings for a new Norcold system (SCQT 4408) is not worth that risk. I'll buy elsewhere next time.

[Richard Kollmann]

mashenden, Unfortunately marine industry products are treated as expendable products like a bread toaster with little or no after market reliable support. It does not matter how much money you spend on a icebox conversion refrigeration unit at some point it will not be economical to repair. Repair or Replace many times depends on manufacturer up grades or system improvements and poor after market technical support. With most of these units produced outside this country or in Job Shops with knowledge of only their systems design. You may find it impossible to contact someone with enough technical knowledge to assist you or help your local service tech engineer.

Manufacturers of pleasure boat refrigeration do not offer training or repair manuals to outlet dealer/distributors nor do they analyze troubles and offer service bulletins. The best advice I can come up with is buy a conventional 12/24 volt fan cooled refrigeration system without extra non productive gadgets like water cooling and add on electronics. Also familiarize yourself with simple non destructive DIY repair techniques.

Pleasure boat refrigeration repair labor costs recently reported for repairing these small units range from $90 to $138 per hour including transportation time. Service call costs on these units range from $200 to $1500 and many times do not correct original problem. Any kind of small Danfoss compressor water cooled condensing system should be rated as unfriendly, less reliable and far more expensive to maintain.

[mashenden]

Sadly, that does seem to be the case.

That said, I will get this unit running if I can get past two remaining obstacles; 1) finding a source for .022" cap tubing (going to .026" doubles the needed length) and 2) figuring out how to jump the thermostat wiring to get the unit to run so I can benchtest it before sinking $200 in a control unit.

It is worth the time/effort IMHO given the unit was damaged during its initial installation, meaning the compressor unit has 0 hours.

Regarding manufacturer's support, would you agree that things would be a lot better if they 1) include a service port because it is not reasonable to think someone should junk a $800-$1300 system because it is low on refrigerant, particularly one that had quick-connects in the design, and 2) make technical drawings available on-line so that the hourly rate or at least the overall cost to have them serviced would go down.

These two changes in the industry would make me want to buy these high dollar products with confidence that I am not throwing my money away.

Just my $0.02 in case a manufacturer is reading.

[azsailor12]

I also have a 4407, but fortunately it's working. The Thetford website has some documentation and spare parts list. It appears that all major assemblies are still available.