Danfoss Electronic Module - Help Needed

[SV THIRD DAY]

If you are not getting an error indication on the LED, them it could simply be that your thermostat is failing and erratically cycling the compressor, because other failure routes should be giving you an error indication. It is pretty easy to check the thermostat.

All you have to do is jumper around the thermostat on the controller with a wire and that should keep the compress running continually. By jumper, I'm meaning removing the current thermostat leads and replacing them with a new wire. If the problem goes away you can suspect and replace the stat, if it continues you can go to the next trouble shooting step.

The thermostat connections are ths No 1 and 3 spade connections on the electronic module counting from the bottom up, so they are pretty easy to identify.

I'm at the desk looking for paperwork distractions all day today, so post what you find here in this thread and I'll get right back to you.

[Richard Kollmann]

Katsumi,
Assuming the LED is Good and its polarity is correct trouble is in the thermostat or an Isotherm added ASU on front of module. This LED must be modified for 12 volt 15 milliamp load or it will go bad quickly.

The first thing I would check is the routing of thermostat's small temperature sense tube. If tube is touching evaporator or cold refrigerant tubing anywhere except where it is designed to touch evaporator a condition like you describe will result.

Next step is to remove ASU if your unit has one and place a jumper wire across Danfoss module terminals C and T. This will allow compressor to run continuously at low speed. If compressor no longer stops problem is most likely the ASU box.

[katsumi]

Hi Rich and Richard
Thank you for your help.
I have fitted a small LED, red to the positive line in and the black wire to the D terminal, is this correct? or do I have to modify in some way?
My fridge is an Isotherm 1130BB1NK0000, it is a 130 litre fridge with small freezer compartment, I am unsure if it has a ASU.
Anyway on your advice Richard I have adjusted the run of the sensing tube and this has done something, it is attached to the evaporator at the top, the sensor may have been touching behind the evaporator. I also put a multimeter across the thermostat and with switch on 1 through 7 had a reading of .465 olms no change not sure if this is correct way to check it? So after defrosting and adjusting the sensor, something has changed, now compressor runs for approx 2 minutes then stops again(more of a pause really) then runs another 30 seconds then shuts off, seems much better except this pause?
I currently have the setting on #2, Yesterday I tried adjusting the cabinet temp by adjusting the settings but I seem to get the same temp 3 degrees C.
Appreciate if you have any other suggestions.
Regards
Nick

[Richard Kollmann]

It is very important to know if this unit has an Automatic Speed Up box mountesd to Danfoss control module. These ASU boxes are a different color green or orange or redish please advise or send picture showing Danfoss module.

Is the thermostat electronic or manual snap action?

There are four things each can cause short cycling, thermostat,wiring, ASU and module. The procedure I listed before would pinpoint the problem.

[katsumi]

Hi Rich and Richard
So after looking through some more of your posts, I have taken the power supply direct from the battery bank, Problem still happens, supply voltage is 14.3
I have then put the metre on the Positive terminal then terminal T, there I have 9.3 volts in between cycles, when compressor kicks in voltage goes up to 12.3 it runs steady for a couple of minutes then voltage will drop to approx 11.4 volts then quickly back to 12.3 volts causing the pause, it will do this a couple of times then it drops to 9.3volt so it stays off for a few minutes then another cycle starts.
Regards
Nick

[katsumi]

Hi Richard
Pretty sure we do not have the auto start device no boxes other than the module. I will try attach some photos of the components

[Richard Kollmann]

Can you identify what the BLUE wires are connected to and where do they go? The voltage readings you are reporting are way out of line. Any voltage below 12.5 can mean on compressor restart a microsecond low voltage spike will prevent compressor from running.

If unit stops for a voltage problem or an amperage problem the LED should flash. Red + LED to Small module + is correct and LED ground to D is correct. Are you sure if the LED is connected direct to battery it will light up?

To eliminate thermostat and its wiring disconnect wires from C and T terminals on Danfoss control module. Then place a jumper wire across the C and T terminals.

[katsumi]

Hi Richard
The blue wires are for the cabinet interior light. I will take the LED off and check it is working, and make a jumper cable and put it across C and the T, then get back to you.
Thank you again for your time.
Regards
Nick

[katsumi]

Hi Richard
I have tested the LED, it is ok.
I took put a jumper across the terminals C and T.
By removing the thermostat wires there is a jumper between C and P which not sure what P is but I did not make a connection to that. The compressor and fan just run not switching off have done for at least 20 minutes now.
I did notice when when I removed the wire from terminal T I saw a bit of heat shrink over the wire, so I removed it and found a resistor inline (see photo).
Regards
Nick

[katsumi]

Hi Richard
Just wondering if you have any other ideas what I could try with this fridge of mine?
Regards
Nick

[Richard Kollmann]

Sorry for Delay in answering I spent some time in the hospital. Let me see if I am correct with where we were in isolating the trouble.

You verified the LED is good and it was wired correct and it did not flash a code when compressor stopped. If this is correct then mechanical overload and voltage problems can be ruled out.

You removed wire if there was one connected to module P terminal allowing standard battery protection of 9.6 volts normal default setting.

After you disconnected thermostat wires C and T from module and placed a jumper wire across Module terminals C and T, compressor continued to run without stopping. By eliminating thermostat and wiring you also eliminated compressor speed resistor. The thermostat circuit is very low current 5 milliamp with no resistance in circuit causing compressor to run at minimum speed of 2000 Rpm. By adding resistance to thermostat wiring milliamp current can be reduced to increase compressor speed.

With compressor performing correctly when terminals C and T are connected together problem must be a poor connection somewhere in thermostat wiring or dirty thermostat contacts.

[katsumi]

Hi Richard
Thank you for you time again.
I did check the LED, also I removed the connection to P. I assume with out connection to P unit will continue to run when supply voltage goes low?
I have had a good look at all the connections for the thermostat, all looked ok. So something has changed, it does seem to run a bit better, not the compressor runs for about 2 minutes then a slight pause happens then it will run about another 2 minutes then another pause 10 seconds another then off for 4 minutes and repeats the above cycle. Just wondering if the pause I am hearing is the compressor changing speed? but the fan is pausing at the same time.
I have made some enquiries to purchase a new thermostat from Isotherm but they tell me they would not have any until June. Would you know of an after market thermostat, or does it have to be specific for this Electronic module?
Appreciate your help with this.
Regards
Nick

[Richard Kollmann]

katsumi, You are not following a normal process of trouble shooting by elimination. Did you not prove that by bypassing thermostat and its wiring that compressor runs continuously without stopping? You also confirmed that thermostat’s temperature sense tube was not touching anywhere it should not. The next step is to eliminate wiring and speed resistor between thermostat and C and T terminals.

To eliminate wiring and resistor disconnect wires from thermostat itself and connect them together and see if compressor will operate normally, if it does then replace thermostat. If compressor does not run correctly with wires connected together then replace wires and Speed resistor.

If you do confirm thermostat is faulty and can not get a replacement you may find an inexpensive thermostat with suction cup used by repairmen as a temporary solution. In the US these universal thermostats are sold by WWW.Granger.com. Check local refrigeration parts stores in your country.

[onestepcsy37]

Richard, hope your hospital was nothing serious. Be well.

[Captn_1]

Hello all.

I was previously registered here, but mainly lurk and haven't logged in for a while. I couldn't recall my original login credentials and the lost password said my email wasn't in the system, so here I am with a new login setup. I won't lose it this time.

I am experiencing an issue with my Danfoss that perhaps you all can assist with. I installed the unit new in 2011 myself. It had been working fine till a couple months ago I noticed it would short cycle. I checked the charge and it was fine, so I left it alone since it seemed to be working otherwise, but it was winter at this point. A few weeks ago I noted it was no longer cooling and the compressor appears to not start (can't hear or feel it). The LED is blinking 3 times. Fan runs.

I have jumped C and T, double checked the charge, checked the ohms across the three pins of the compressor (2.2 ohms on all). Voltage is 13.5 with battery charger turned off with fridge off. Turn on fridge and voltage drops to 13.4 for a second when the fan kicks on, but then is back to 13.5 as the fan runs (so no voltage pull like the compressor even tried to come on). Disconnected the fan with no change.

Does this sound like the control module? If so, Mr. Kollmann, are you still testing the units at no charge and selling them for ~$150 plus shipping if a module is bad, while returning it for $20 if it is good?

Thanks so much.