3 flashes on Danfoss control

[Akka]

We've been running a Danfoss BD50 for 5 years or so and it's worked well. Sometimes at startup we get three flashes from the LED but repeated tries (8 or 10, 10 seconds apart) have always "fixed" the problem. Alas, not this time. We removed some of the refrigerant in case it was overcharged. Still no joy. So we looked at voltage. About 12.8 V. But then when turned on the switch we were surprised to see no voltage drop, not even 0.01V on our digital multimeter. I infer the compressor is drawing no current at startup. So how can the controller be detecting an overload?

The one piece of this whole system that can be easily removed is the controller. Should we get it checked? If so, where?

[puffcard]

Three flashes means the compressor can't get started. My understanding is if you get the three flashes right away, you have a problem with the electronics and controller must be replaced. If it starts and chugs a while, could be thermostat or power interruption/connection. Fan and/or pump will continue to run with 3 flash fault, so make certain you aren't hearing that. Most of the time three flash is not the compressor. The controller is a easy change out and it's not a bad part to have a spare if it turns out to not be the problem. Remember a controller is cheaper than a service call. Good Luck.

[Richard Kollmann]

Originally Posted by Akka

We've been running a Danfoss BD50 for 5 years or so and it's worked well. Sometimes at startup we get three flashes from the LED but repeated tries (8 or 10, 10 seconds apart) have always "fixed" the problem. Alas, not this time. We removed some of the refrigerant in case it was overcharged. Still no joy. So we looked at voltage. About 12.8 V. But then when turned on the switch we were surprised to see no voltage drop, not even 0.01V on our digital multimeter. I infer the compressor is drawing no current at startup. So how can the controller be detecting an overload?

The one piece of this whole system that can be easily removed is the controller. Should we get it checked? If so, where?

Three LED code is an overload amperage signal if it is the first code displayed. If no one has tampered with refrigerant problem is not likely too much refrigerant. Because eventually the compressor after several tries will boot up OK it is also not likely a faulty module. A low or dirty current to these variable speed BD50 compressors in boat’s refrigerator wiring has been know to trigger 3, 4,and 5 LED codes.

When reporting refrigerator problems on BD compressor systems you can get more precise help if you identify the manufacture and model of the system. There are over 100 applications in use today for this type compressor. Troubleshooting the 3 LED code is not the same on each manufacturers system. On Adler Barbour units troubleshooting must include the electrical board, EZ Kold would include seawater in refrigerant, Water cooled and keel cooler units compressors oil contamination do to compressor heat, to name a few.

Suggestions

Follow up by describing your unit and its maintenance history.

Run correct size and correct polarity fused jumper wires direct from a fully charged battery to module in order to bypass all boat’s wiring. Volt meter readings are of no value, Compressor still does not run electronic module needs to be tested on another unit.
If your shipping address is in the US I will test at no charge your module on my Danfoss compressor refrigeration test stand. This test stand will run at max compressor load for a one hour. Because of the start up problem I will extend run overnight monitoring cycle times. I will then return your module to you insured Priority shipping and handling charge of $20.

[Akka]

Richard, thank you for the good information, always. I went out and bought a new controller. I got the 3 flashes once, then the compressor started fine. So as you say, it probably wasn't the controller after all. Oh well, now we own a spare controller[emoji3]

The system is home built, using the holding plates and copper tubing from the original 1980s era A/C system. The BD50 compressor is wired directly to the house bank, with just a switch and a fuse in line. All connections look good.

In any case it's running again. But I'm a little concerned about the oil. We've had several leaks, replaced the dryer, etc. over time and I'm afraid I might have reduced the oil too much. I let a little gas escape from the high side and it didn't feel very oily. Can I add oil without draining and vacuuming the system? If not, how do I get oil into the system without risking some air gets in, too?

[Typhoon]

If you built this system from an old AC system there is a good chance you have larger tubing and you could be getting oil collecting inside the low spots. These small compressors have very low refrigerant velocities and will have a hard time returning oil to the compressor in larger tubing . 1/4" is usually the best to use .

You can charge the oil with something like this ,
Set of 3 R-134a Refrigerant Ester 100 Oil Charge Auto Air Conditioner 3oz. #312

Regards John

[Akka]

Originally Posted by Richard Kollmann

Three LED code is an overload amperage signal if it is the first code displayed. If no one has tampered with refrigerant problem is not likely too much refrigerant. Because eventually the compressor after several tries will boot up OK it is also not likely a faulty module. A low or dirty current to these variable speed BD50 compressors in boat’s refrigerator wiring has been know to trigger 3, 4,and 5 LED codes.

When reporting refrigerator problems on BD compressor systems you can get more precise help if you identify the manufacture and model of the system. There are over 100 applications in use today for this type compressor. Troubleshooting the 3 LED code is not the same on each manufacturers system. On Adler Barbour units troubleshooting must include the electrical board, EZ Kold would include seawater in refrigerant, Water cooled and keel cooler units compressors oil contamination do to compressor heat, to name a few.

Suggestions

Follow up by describing your unit and its maintenance history.

Run correct size and correct polarity fused jumper wires direct from a fully charged battery to module in order to bypass all boat’s wiring. Volt meter readings are of no value, Compressor still does not run electronic module needs to be tested on another unit.
If your shipping address is in the US I will test at no charge your module on my Danfoss compressor refrigeration test stand. This test stand will run at max compressor load for a one hour. Because of the start up problem I will extend run overnight monitoring cycle times. I will then return your module to you insured Priority shipping and handling charge of $20.

Richard,

I ran the jumper cables test you suggested, and still no go. The refrigerant has been messed with plenty -- I've had leaks, repaired them, evacuated the system and refilled it several times in the last 10 years or so since I built it. I think it still has a leak somewhere but we go a year or so without having to top up the system.

Two things bother me. The first is, how can too much refrigerant be the problem after the system has equalized completely? The documentation says the three flashes indicate too high a differential in pressure, but right now, the pressure differential is 0! The static pressure is about 35 psi, so there shouldn't be any condensed refrigerant in the system (ambient temperature is about 65°F).

I measured the amperage at startup, and it's less than 0.1A until the LED starts blinking and the fan comes on. Once the fan is on, there's about 0.5A, as you'd expect from that fan. If the compressor is somehow jammed, I'd expect infinite current at startup, rather than negligible current.

In any case, does your offer still stand, to test the controller? If so, how can I take you up on it? I don't think I have your address.

Cheers,

Rob

[OzePete]

Rob, remove the electronic unit completely from the compressor. Use a multi-meter to check the ohms between each two of the three terminals on the compressor. (Each terminal represents a leg of one of the three motor windings and any combination should read about 2.0 Ohms. If one pair indicates an open circuit then the compressor is shot. Possibly due to oil starvation caused by oversized evaporator tubing as John suggested.

[Richard Kollmann]

Danfoss’s new variable speed direct current BD compressor systems require a different trouble shooting program than other electrical compressors. The BD 35 and BD 50 compressors are designed to be controlled and monitored by voltage and amperage not refrigerant pressures. Low on refrigerant will not prevent this compressor from running but too much refrigerant will. Static pressure on a 70 degree F day of less than 45 psi will not cause an overload.
• If control module sees a high or low voltage spike lasting only a few milliseconds, many times too quick to see on a voltmeter compressor start up electrical pulses are terminated at module. LED trouble code one flash every 4 seconds.
• If an overload condition exists on start up high amperage at module will terminate start sequence. Air cooled Danfoss BD Compressor rarely fail although water cooled compressor with out supplemental cooling have experienced system failures. The Three LED code does not always identify a faulty compressor. The most likely overload signal on the BD35 and BD50 is weak or dirty refrigerator power wiring during compressor start up. The correct troubleshooting is to bypass all power and ground wiring from module to battery. A poor ground system may not trigger a trouble code but will alow compressor to run single phasing pulses to compressor rotor producing little or no cooling. Fan wires on Control module are limited to ½ amp amperage above this will cause control module to terminate electrical pluses to compressor.

Correct trouble shooting for standard configuration Danfoss BD compressors:
Disconnect non standard gadgets from control module including thermostat wires and place a jumper wire between terminals C and T. Compressor still does not run.

Disconnect Black fan wire from F- Terminal. Compressor still does not run.

Bypass Power and ground wires from Control module and connect direct to battery terminals. Still does not run.

You could try OzePete’s Pulse coil ohm test including no continuity from any post to case ground.

After following the above tests I would try another control module. Danfoss has worked through over 15 different control module designs and still have trouble with control modules standing up to a mobile marine environment.

[OzePete]

OK so maybe it's a good time to provide a 'KISS' list of things to check if your DC compressor will not run: (This is a check list we send to our Ozefridge customers and others if needed.)

First disconnect any high voltage supply.

1:Check DC voltage-in on the compressors electronic unit, both with compressor off AND when it runs or tries to run.
A: If the voltage is low, or if the voltage is OK but drops away more than say half a volt at start up attempt, then check the power supply, terminals, wiring and batteries. (An amp meter reading when attempting to start would be useful. If the amps go way above normal then the compressor may be mechanically stuck.). If the voltage is OK and there is little dip upon a start attempt then go to step 2.

2: Bridge the lowest and third lowest terminals and power up. (These terminals C & T on Secop, Danfoss and most other compressors, are the thermostat switch)
A: If the compressor starts and runs normally, leave the bridge in place and run manually until you can replace the thermostat. (YOU become the thermostat!) If still not running go to step 3.

3: Remove both fan wires from electronic unit and attempt a start.
A: If this allows the compressor to run, replace fan. Note.. fan should not exceed 6 watts. If still not running go to step 4.

4: Remove electronic unit from the compressor revealing three terminal pins on the compressor. Use a multi-meter to check resistance between each combination of two pins (of the three) and from these pins to the compressor case (Ground)
A: The resistances should be uniform at approx 2.0 Ohms for BD50, 2.3 Ohms for BD35. Others may have different Ohms readings but OK if they are all similar. If there is no reading or a much higher reading between the pins or if there is leakage to the ground then the compressor is dead. If the readings are OK the compressor is most likely OK so go to step 5.

5. Replace the electronic unit.

I hope this helps..
Cheers, Ozepete from Ozefridge.com.au

[Richard Kollmann]

Pete, I receive three to five emails a week asking for help when a Dafoss BD compressor fails the start boot up sequence. What is the next step recommendation when you’re troubleshooting and module replacement does not solve the no start up problem? Do you Start over with recommend tests again, Add more oil, Dehydrate vacuum and add correct amount of Danfoss recommended refrigerant, Replace Evaporator flow expansion device, Replace compressor or replace complete system?

[OzePete]

Good question Richard but if the system passes the first four steps I described then it is highly unlikely that the compressor is faulty. These suggested steps are in order of likelihood of identifying the fault.
As you know by far the most common cause of DC system failure to run is a faulty power supply, so step 1 will identify the cause in most cases . Past history helps greatly in system diagnosis but If a system that has been running ok for years then suddenly fails, these steps should isolate the fault. If the compressor is not mechanically stuck and therefore dead (as in step 1) and it has similar resistance between any pair of the compressor terminals and no continuity to ground (as in step 4) then it should run.
In the most unlikely event that having passed steps 1 to 4 and the electronic unit replacement does not solve the problem, I agree firstly double check steps 1 to 4, otherwise replace the entire system.
Your final question is similar to those we ( and most likely you too) receive from some so called refrigeration mechanics who simply should never be allowed to touch any equipment. The try this, woops that don't work so lets try this method is a sure sign of a mechanic with no analytical abilities. They make me shudder and worse still when a client is at an island in the mid Pacific and the local 'refrigeration guru' has to ask "what is a vacuum pump" OMG!

Cheers OzePete from ozefridge.com.au

BTW Richard, feel free to use/ forward the check list to your contacts if it will help, but please acknowledge as being from Ozefridge.. thanks

[Akka]

Problem solved! Thanks to OzePete and Richard for all the good advice. In the end, it was Pete's continuity check that did the trick. Two of the pins showed negligible resistance, but the remaining pin was completely isolated from the others. Even though compressor failure is rare, I'd recommend that test early in the diagnosis, simply because it's so easy to do. So we bought a new compressor, screwed it down and soldered it in, and the system is now working great, using the original controller. We're keeping the new controller as a spare.

I have one question, just out of curiosity. The compressor (like all hermetically sealed units) comes with three ports -- suck, discharge and "process". When we installed the previous compressor we soldered a separate valve fitting on the process port, but after viewing several YouTube videos about compressor installation, this time we just left the cap on that port. My question is, if there's no use for that port, why didn't the manufacturer permanently seal it before sending it out?

Again, thanks guys for the help.

[OzePete]

Pleased you were able to sort that out but you need to do some more... sorry! The cap on the compressors process port should be removed and a service valve welded in there...
Cheers,
OzePete Ozefridge

[Richard Kollmann]

Pete, I would not recommend your five step troubleshooting checks as checks one and four are only another way to sell more refrigeration units. The Danfoss compressor’s control module start boot up sequence measures voltage and amperage in micro seconds, just like your home or office computer. Would you check the same microprocessor in your computer with a volt meter.

Checking resistance of internal field coils or speed transducer coil in four pin model compressors is not likely to confirm a bad compressor on air cooled Danfoss BD refrigeration systems. Any resistance of less than 5 ohms is tricky to read and easily mistaken.

After thirty five years of instructing DIY boat refrigeration troubleshooting a 12/24 volt Danfoss compressor with a volt/ohm meter is a mistake. I have not as yet tested the latest standard Secop 101N0212 replacement control module’s start up boot limits but until I do I recommend avoiding use of voltmeter module tests unless you have Superman’s eyes.

Pete, your five step troubleshooting guide also does not include a method of detecting pulse phase disruption on variable speed BD compressors giving a LED trouble code of three or more flashes.

[OzePete]

Originally Posted by Richard Kollmann

Pete, I would not recommend your five step troubleshooting checks as checks one and four are only another way to sell more refrigeration units. The Danfoss compressor’s control module start boot up sequence measures voltage and amperage in micro seconds, just like your home or office computer. Would you check the same microprocessor in your computer with a volt meter.

Checking resistance of internal field coils or speed transducer coil in four pin model compressors is not likely to confirm a bad compressor on air cooled Danfoss BD refrigeration systems. Any resistance of less than 5 ohms is tricky to read and easily mistaken.

After thirty five years of instructing DIY boat refrigeration troubleshooting a 12/24 volt Danfoss compressor with a volt/ohm meter is a mistake. I have not as yet tested the latest standard Secop 101N0212 replacement control module’s start up boot limits but until I do I recommend avoiding use of voltmeter module tests unless you have Superman’s eyes.

Pete, your five step troubleshooting guide also does not include a method of detecting pulse phase disruption on variable speed BD compressors giving a LED trouble code of three or more flashes.

Not sure what your problem is Richard.
Often when people from the refrigeration industry, like myself, John and others assist a poster with refrigeration problems, you come back with 'cherry picked' nonsense like this! The diatribe you posted this time is not just irrelevant point scoring nonsense but an inference of impropriety directed at myself and other industry suppliers to which I take offence!

But now that you have moved the goal posts, let me respond similarly,..
Also it may come as a shock to you but I and many others also understand the electronic driver of these units and how they function, but not many posters do or want to. It's about being practical not point scoring!

It has been my experience that when a user finds his refrigeration system is not working he / she simply wants to locate the problem part or cause, and needs to do this with whatever means are available. The chance of there being even a old CRO or any other digital apparatus under the 'forward bunk' to test the pulse width, frequency, THD or whatever, is somewhere between zero and none, while most likely there will be a multi-meter to be found! Get it?

The 5 point test I suggested is practical and an aid to locating the faulty component and it works. (Read earlier post!) If you have a simple better method why not tell us about that instead of rubbishing what others contribute.

And finally Richard, I started posting here because there was so much incorrect refrigeration information and often simple situations were grossly complicated. I wanted to assist with SIMPLE resolution processes that are relevant to the poster and their situation, specially those not in a well equipped laboratory!

Unlike one 'expert' here I won't bore people to tears using up much of my posts telling all and sundry how great I am, my vast experience then drift off into irrelevant complicated drivel in some sort of attempt to promote my self interest, ego or sell books!
Cheers, OzePete ozefridge