Danfoss control box off Waeco CR110

Aussieroo · Member

Danfoss control box off Waeco CR110

Aussieroo · Member

I don't know what happened to my posting. I hope I don't now double up. The topic is still here but all my text and photos did not seem to make it to the post, so will do it all again.

I own a Waeco CR110 caravan fridge that I have had trouble with since its first outing 2 years ago. On its first trip I had the Danfoss controll box replace under warranty in Mildura.

All seemed to work well and now I am on to my 4th control box. I have turned the fridge off afer making sure it worked on the new box until I find out what is causing the problem.

As our local technician that does the Waeco/Dometic repairs is off until after Easter I wanted to see if I could get some idea where to start looking for a cause. The photos below are of one full

Board and one of the second box and where it has blown and one of the latest one with less damage but still in the same area. Any help or ideas of what to check would be great.,

I have it connected to a 130AH AGM battery with a 15 AMP fuse on the positive line. The 240 side has a 4 AMP fuse located inside the box. None have fused. I also have a van mover

that runs off the same batter with its own wiring and fuses. It is also wired via Anderson plugs allthe way through the battery isolater to the cars battery and Altenator. The polarities are fine

and round the correct way. Is there a way that a spike can be coming back from the fridge through one of the 3 wires that exit the control box and plug into the fridge?

Thanks in advance

Ralph

valiant81 · Senior Member

Hi Assieroo;

While i can't help with the repair, but for my 2'c worth what could be happerning is the spikes that are caused by the motor that drives your caravan mover could be causing spikes that apear on the 12 volts that also run your fridge, these spikes may be to much for you fridge electronics to handle and cause the failure. Only way would be to disconnect the 12 Volts totaly from you fridge.

Why not contact Dometic and have a talk with their sevice department, maybe after you have told them of your tail of woe, they may come to the party for the total cost or maybe just the parts, as a good will jester, worth a try.!!!

oldtrack123 · Guru

HI

FOUR boards , you are a patient person

Has the serviceman check the motor load currents ??

Just looking, it is hard to say what has caused all three to overheat .

While it could be voltage spikes I have a feeling that is not the problem since other components closer to the 12V input appear OK.

In any case it would not do any harm to remove the chance of voltage spikes due to the van mover

get a capacitor from Jay car part #RE-6236 & connect across the van mover pos & neg terminals

Make sure you have the capacitor polarity right [ get Jaycar to show you which must go to the positive]

PeterQ

Aussieroo · Member

Offending short

I think we have finally found the problem. I have an electrical mate come around to put a second pair of eyes over this problem and he suggested I take this plug off the fridge unit.

It is the plug that the black control box plugs into with the 3 black wires. As soon as we had it off we could see what was happening, This looked to us something that has been there since this was built

and only became an issue when driving on 12V It would short out to a body screw picture above and blowing the power exit side of the box. Anything on the front end would have either blown the fuses or the input side of the board.

Now to fix the issue and see what Waeco/Dometic have to say. The local repairer rulled out any warranty as it was over 2 year old!! My mate who has the same fridge will be checking his out now as well. I guess I just got the one bad one in the batch.

Ralph

Aussieroo · Member

Thanks Peter I will do that tomorrow and fit it as well just to be on the safe side.

I tried to remove the duplicate post but don't seem to be able to from this forum.

Still cant work out why my original post didn't show up which caused me to repost it.

Aussieroo · Member

oldtrack123 wrote:

HI
FOUR boards , you are a patient person
Has the serviceman check the motor load currents ??

PeterQ

The fourth board is now the good one currently in the fridge. The first was replaced under warranty the second happend about the same time I was wiring up the cables and anderson plugs and regulator to the car so I wrongly assumed

it was something I had done looking at the nature of the failure. Seems after the last on I was beating myself up for no good reason. The Tech as I have stated is away on holidays for another week or so. This failure it seems happend either while the van was moving with some vibration or while I was taking the fridge out of its place in the van. Whilst sitting still it was fine.

DeBe · Guru

Personaly at that price I would try & repair it, as the burnt out power MOSFET is a IRF7343 & quite cheep on Ebay from China. Only about $5 for 5 of them freight free.

Aussieroo · Member

DeBe wrote:
Personaly at that price I would try & repair it, as the burnt out power MOSFET is a IRF7343 & quite cheep on Ebay from China. Only about $5 for 5 of them freight free.

Thanks for the heads up. I will find them on ebay and see how we go. I think I would do the second box whic appears to have less damage. Being a bit of a novice on boards, what are the components immediately before MOSFET that three of have been burnt on the first board. Do you think looking at the second board that they might need replacing? They dont appear damaged to my eye.

Aussieroo · Member

There is hope yet, I did receive a reply from Waeco and they have forwarded my problem to their supervisor who unfortunatel is on holidays also until after Easter. Wait and see if they offer any compensation. I only asked for a new control box, no other out of pocket expenses.

dorian · Guru

I would avoid eBay for power transistors. Too many fakes.

au.rs-online.com/web/c/semiconductors/discrete-semiconductors/mosfet-transistors/

dorian · Guru

The "330" components appear to be 33 ohm resistors. They could be 330 ohm, but your multimeter should tell you one way or the other.

That said, the fact that these gate drive resistors have failed suggests that the 16-pin IC (level translator ?) may also have failed.

DeBe · Guru

The IC is a HCF4050 Hex Buffer Converter (non inverting) Jaycar ZC4050 .95c each. Just checked the resistors on my board with meter & they are 33ohms.

-- Edited by DeBe on Thursday 2nd of April 2015 07:15:52 PM

Aussieroo · Member

I had a phone call from the head of the Dometic service department today and the upshot is they want to offer me a refund for the balck control box so long as I supply them a receipt.
He was very helpful and appreciative for my info and photos on a problem they apparently have not encounted before. The will include it in their next service conference.
Fhanks again for the info, Not sure I am that clever to repair it. Will check with some mates with more skills in this area.

DeBe · Guru

Well that's good news.

valiant81 · Senior Member

Hi dorian;

you are right, 33 Ohms.

-- Edited by valiant81 on Friday 3rd of April 2015 11:26:37 AM

dorian · Guru

I don't understand how the circuit works.

According to the following document, the P-channel MOSFETs are powered from a supply that varies between 27VDC and 45VDC, depending on the RPM.

http://de.refrignet.danfoss.com/TechnicalInfo/Literature/Manuals/06/electronic_unit_101n0500_voltage_04-2008_en100a102.pdf

The speed of the BD compressor is proportional with the voltage [to] the compressor motor. The compressor motor is designed to run between 2000 and 3500 rpm.

In order to decrease power leakage, the current to the compressor is reduced by increasing the voltage applied to the compressor motor. For this purpose, there is a boost converter in the electronic unit that is able to step up the applied voltage to a voltage between 27 and 45V DC. That means if 2000 rpm is requested, the voltage out of the boost converter is 27V DC and if 3500 rpm is requested, the voltage out of the boost converter is 45V DC.

The HCF4050 has an absolute max supply rating of 22V (18V max on the inputs), and I would expect the the Dialog microcontroller would be powered from +5VDC.

http://doc.chipfind.ru/pdf/stmicroelectronics/hcf4050.pdf

So how does 5V logic manage to control 45V MOSFETs via a 4050 hex buffer?

My second question is, how does the circuit ensure that the max Vgs rating of -20V is not exceeded for the P-channel MOSFETs?

-- Edited by dorian on Saturday 4th of April 2015 10:57:00 AM

DeBe · Guru

The HCF4050 has 12Vdc on its power pin, & are capable of max 22V. The IRF7343 N-CH +55V. P-CH -55V. Quite within the operating range. They obviously seem to work ok un less you short one of the compressor feeds. The module I have the 240Vac part was destroyed by over voltage.

-- Edited by DeBe on Saturday 4th of April 2015 12:21:28 PM

-- Edited by DeBe on Saturday 4th of April 2015 12:23:15 PM