Isotherm Cruise 85 caput.

[GeorgeRa]

Out fridge forced our early departure from the beautiful Beachside State Park. This is what happen with our 85l Isotherm Cruise 101N0510 with compressor Secop BD35F/BD50F with SEC (Smart Energy Controller):
- Cooling stopped
- Compressor stopped, no noise
- Fridge interior light doesn’t work
- SEC Thermostat dial can turn the fan on/off
- Doesn’t work on AC nor DC power (it is 101NO510 dual power unit)
- AC nor DC CBs were triggered.

My guess is that the SEC (or its wiring) failed because:
- Power is getting to the SEC because the fan can be turned on via the thermostat pot
- Power is not getting to the light and the compressor.

Next step is to verify if indeed the SEC is the problem but fridge needs to be removed.

I have 3 reasonable options both requiring fridge removal:
1. Find another discontinued now SEC (easy replacement but scavenging price at $320)
2. Replace SEC with capillary thermostat (could require extensive disassembly to place the bulb on the cold plate)
3. Replace SEC with its replacement - ITC (finding a good place for the outside display could be difficult)

Thoughts?

[mikeehlert]

Pull the fridge and find the problem before you try to solve it.

[booster]

Originally Posted by GeorgeRa

Out fridge forced our early departure from the beautiful Beachside State Park. This is what happen with our 85l Isotherm Cruise 101N0510 with compressor Secop BD35F/BD50F with SEC (Smart Energy Controller):
- Cooling stopped
- Compressor stopped, no noise
- Fridge interior light doesn’t work
- SEC Thermostat dial can turn the fan on/off
- Doesn’t work on AC nor DC power (it is 101NO510 dual power unit)
- AC nor DC CBs were triggered.

My guess is that the SEC (or its wiring) failed because:
- Power is getting to the SEC because the fan can be turned on via the thermostat pot
- Power is not getting to the light and the compressor.

Next step is to verify if indeed the SEC is the problem but fridge needs to be removed.

I have 3 reasonable options both requiring fridge removal:
1. Find another discontinued now SEC (easy replacement but scavenging price at $320)
2. Replace SEC with capillary thermostat (could require extensive disassembly to place the bulb on the cold plate)
3. Replace SEC with its replacement - ITC (finding a good place for the outside display could be difficult)

Thoughts?

IMO, the best solution isn't available, and that would be to use the capillary thermostat but with a soft start and speed control on it. This is based on what we have seen with our new Cruise 85 Elegance with the ITC.


I still haven't decided for certain is we will keep or ditch the ITC because it has the softstart feature but other shortcomings.


Mounting a capillary tube thermostat in is not that big a deal usually as long as you have the bracket to hold the tube to the top rear of the freezer compartment. It is inside the compartment in stock form, but I ran ours in the same area but outside on top of the freezer box for most of the time we had our first 85 and it seemed to work better. The freezer box came loose with just two screws in the front that also held the freezer door on and then you just pull it out and down a bit to get at it. The wires should still be there, I hope, as they all came with the capillary in them I think. The biggest amount of work would be pulling the frig to get to the wiring, maybe. I know it is on ours.


The ITC box is large and kind of ugly and is tough to find a place for sure, but you can surface mount it also, or make a smaller mounting, I think.


Even if we keep the ITC in place, it will still have the capillary mounted in place as well as an added this winter control for the capillary with speed control and on/off switch. I will be changing the wiring a bit to get the ITC capacitor moved to make the wiring correct for each option. When I installed the unit, I made it easy to switch back and forth between capillary and ITC to cover the possible electronic failure of the ITC and I think your issue with the SEC reinforces the need to do that.


Whether or not you fix the SEC, or go to the ITC, I would still recommend putting in a capillary for emergency use so another trip doesn't get ruined in the future from a similar failure.


If you do use the ITC be sure to mount it so it doesn't display toward the sleeping area as it is as bright as a flashlight and might keep you awake. Waste of energy and can't be dimmed or made to time out so pretty poor design that way.

[@Michael]

Can you wire the 101N0510 directly and bypass the SEC long enough to determine if the 101N0510 and compressor are functional? That would tell you if the compressor is functional.

When I had trouble with my 101N0510/BD35 Novakool, the mfg. had me jumper a couple wires on the 101N0510 and force the compressor to run 100%.

Original wiring diagrams for the 101N0510 are available from Secop.

[booster]

Originally Posted by @Michael

Can you wire the 101N0510 directly and bypass the SEC long enough to determine if the 101N0510 and compressor are functional? That would tell you if the compressor is functional.

When I had trouble with my 101N0510/BD35 Novakool, the mfg. had me jumper a couple wires on the 101N0510 and force the compressor to run 100%.

Original wiring diagrams for the 101N0510 are available from Secop.

All you would need to do would be to remove the wiring for the SEC so they won't interfere with anything and then jumper the thermostat wiring which will simulate using a capillary mechanical thermostat. I think on the 510 it is 3 wires to connect but two are just the same wire connected to two terminals on the control board. With no resistance you will get low speed only increasing with resistance to 3500 at 1523 ohms.


Terminal C and P connected to one wire of jumper (some drawings show the DC only without the P connection)


Terminal T to the other wire with no or the resistor of your choice

[themexicandoctor]

Booster,

It's been a while - excellent answer as always - are you saying that in the last 12 months or so you have replaced the Isotherm you purchased a few years back? I don't eat ice cream so went with the Novakool R3800 instead, a crude design but simple & bulletproof but the Isotherm was my next choice.

[booster]

Originally Posted by themexicandoctor

Booster,

It's been a while - excellent answer as always - are you saying that in the last 12 months or so you have replaced the Isotherm you purchased a few years back? I don't eat ice cream so went with the Novakool R3800 instead, a crude design but simple & bulletproof but the Isotherm was my next choice.

Yep, or old Isotherm started to lose cooling capacity on our spring trip this year and we just limped it through. Not an electrical problem and it still ran so must have been on internal issue or freon leak. It was 10 years old, though.


The Novakool and Isotherm use the same Danfoss compressors, although the condensers are different styles. The mechanical thermostats tend to be the biggest issue in both brands, from what I have seen, read, and experienced.

[themexicandoctor]

10 years of perfect service is excellent for a RV Fridge.

[GeorgeRa]

Thank you all for help. After returning home we found the fridge was still cold, surprised, but “blamed” it on good insulation. This morning I found more time to continue the quick and inconclusive Beachside troubleshooting. In the quiet garage listening to the compressor hum was easier and I could use tools I didn’t have.

To my surprise, fridge works on AC and DC power, I can hear the compressor hum, freeze compartment gets cold in minutes, ME-ARC50 show current draw. Light didn't work. I pulled the LED light bulb which gave me a moment of sudden realization but not by its light, but by its darkness. A few years ago, I replaced the incandescent light bulb with an LED one. The LED failed miserably. During the beachside troubleshooting I used the lightbulb as an indicator of power getting into the compressor but should have use ME-ARC50.

Big mistake.

Tracing back failures troubleshooting steps with new info I think that the most probable cause was the LED bulb failure causing CB disconnect.

Intermittent wiring or SEC failures are still possible but unlikely. I am contemplating stove removal to access SEC from the top to check wiring.

[GeorgeRa]

I didn’t think about possibility of LED bulb short blowing fridge CB, perhaps I was extrapolating incandescent failure into the LED world. I have a lot of LED lamps (LED chips integrated into lamps) in our van and zero failures over many years.

I just bought an Isotherm LED festoon lightbulb, $18 so must be gold plated, hopefully it will work.

LED bulb for Isotherm refrigerators [IS-SEC00038DA] - $18.00 : Isotherm-Parts, Isotherm Marine Refrigeration and Parts

[booster]

Originally Posted by GeorgeRa

I didn’t think about possibility of LED bulb short blowing fridge CB, perhaps I was extrapolating incandescent failure into the LED world. I have a lot of LED lamps (LED chips integrated into lamps) in our van and zero failures over many years.

I just bought an Isotherm LED festoon lightbulb, $18 so must be gold plated, hopefully it will work.

LED bulb for Isotherm refrigerators [IS-SEC00038DA] - $18.00 : Isotherm-Parts, Isotherm Marine Refrigeration and Parts

I wouldn't be surprised that in the process of failing, the light might have put some funny stuff on the C terminal which is shared with one of the temp sensor wires most likely.


An interesting thing along those lines is that with the ITC, they have put a capacitor between the two temp sensor wires, and IIRC in the early wiring diagrams they didn't have that there, so they may have had some noise issues with the ITC also.

[GeorgeRa]

I got an LED bulb from Isotherm, to my surprise it needs to be installed with correct polarity.

[booster]

Originally Posted by GeorgeRa

I got an LED bulb from Isotherm, to my surprise it needs to be installed with correct polarity.

I put a similar one in our old frig and it, too, was polarity specific.

[Bud]

Originally Posted by booster

I put a similar one in our old frig and it, too, was polarity specific.

Same here in the overhead area booster, in the 05/04 190P. 3 of them, the middle one is the van, the outside 2 are the B.

Now Listen Up. During Ida, I had the following happen:

One of the bulbs went south, about 1/3 brightness and led's out. Will need to change it out. Came back about an hour later and duh, it was fine. Next day, it was dead. Replaced it, and the next was at half speed. Later, just fine, go figure.

Third one, no good. I had purchased a set of five, tossed them out and started over. All good so far, 3k+ trip since and all is well with another, different set.

Bud

[GeorgeRa]

Had some time to mount my new Isotherm LED light bulb and run into another surprise with the fridge. To check polarity I used voltmeter, and got 27VDC (likely nominal 24VDC). All manuals state 12V 3A max light bulbs, and my previous bulb was 12VDC 1W, but at 24 VDC it fried beautifully.

I have AC/DC Isotherm Cruise 85L which uses 101N0500 Secop electronic unit which also states to use a 12VDC bulb - “Lamp (optional, Fig. 1) A 12V DC 5 Watt lamp (10) can be connected between the terminals A and C. The output voltage between the terminals A and C is always regulated to 12V DC. A 12V DC lamp must be used for both 12V and 24V power supply sys-
tems.The lamp output can supply a continuous current of 0.5Aavg.”

I checked light supply voltage on AC and DC powered, as I thought on AC it provides 24VDC (27.3V) and on DC it provides 12VDC (13.4V).

It seems as 101N0500 is not converting AC to 12VDC for the lightbulb, don’t know what it does for the fan nor the compressor without the fridge removal. I very much doubt Secop/IndelWebasto would design different bulb voltage for AC or DC choice.

I think there are 2 potential issues:

1. Secop and IndelWebasto manuals are incorrect and light bulbs provided are for the range from 12 to 24VDC. The LED bulb by Isotherm has no voltage nor wattage printed, very unusual for European light bulbs.

2. The 101N0500 unit is malfunctioning. This part number is no longer available but a newer and improved 101N0510 control electronic units are avialable.

I am waiting for reply from IndelWebasto to shed some light on this issue.

[GeorgeRa]

I talked to Isotherm folks. Based on my information they diagnosed that the 24VDC to 12VDC lightbulb converter, an integral part of the 101N0500 failed. This failure has no impact on neither compressor nor fan power controls.

Possible solutions:

- Replace 101N0500 (new 101N0510) Amazon $245

- Add 24VDC to 12VDC converter for light bulb $15

- Use 24VDC bulb. My purchased LED bulb from Isotherm # IS-SEC00038DA is for 24VDC according to them so it is my solution

- Not use any light

[@Michael]

Interesting.

Is it possible that the compressor is also running on 24V when plugged in to shore power?

[GeorgeRa]

Originally Posted by @Michael

Interesting.

Is it possible that the compressor is also running on 24V when plugged in to shore power?

I would think that Secom compressor is powered the same way on AC or DC power. A 101N0510 is 12/24V but I think compressor is running at 12V.

[GeorgeRa]

My fridge is still acting, sometimes it works sometimes it doesn’t. It fails randomly on either AC or DC power. I left it on yesterday on, worked well but this morning was off. When it is working it cools very well. So most likely the issue is caused by either faulty wiring, Smart Controller (SEC) or SECOP 101N0500. The compressor controller has internal failure providing 24VDC instead of 12VDC to the fridge light so it is probable that controller damage is more extensive.

My plan is to use an inexpensive capillary thermostat ($11 Amazon) to bypass SEC and test the 101N0500 controller. Depending on results of this test my potential options are:

If 01N0500 with mechanical thermostat works:
1. Install original Isotherm Thermostat - $65

If 01N0500 doesn’t work:
1. Install a new version controller 101N0510 - $220 with original Isotherm Thermostat - $65 = $285
2. Install a new version controller 101N0510 with Intelligent Temperature Control/AC/DC Kit 12-004 - $375
3. Get a new Isotherm Cruise 85 refrigerator – $1167 to stainless steel $1572

[avanti]

Do you know about the LED diagnostic light that you can install between the + and the D terminals? It will flash error codes when something is wrong.