espar hydronic d5 controller failure mode

markxengineering

Active member
Yes it’s just a 12v signal, the rest is handled internally (minus diagnostic functionality, which is a nice feature)

@outbound, the diagnosis is covered earlier in the thread. Nothing to do with the silicon remnants left over from deporting.
 

drew502

Member
It's dead again! I'm waving the white flag, it was fun to troubleshoot but now I want it to work. In looking for a replacement ECU, I came across this one
https://heaters4you.com/eberspacher...001.html?search_query=control+unit&results=66

Advertised for Mercedes Vito, not Sprinter, but it is a D5WZ. Anyone know if that would work? I'll do some calling around tomorrow.
@markxengineering - Were you ever able to determine if this ECU would work with a Sprinter Hydronic Espar?
 

DIYRV2020

Active member
I got the similar issue on the D5WZ heater on my 2005 Sprinter 3500, heater won’t start when turning on the heater booster switch, AP200 scanner reported 0802 / blower motor has open circuit fault code. I decided to depot the control module since the other heater parts are in pretty good condition.

Long story short, I depotted it, cleaned the potting material pretty good from the PCB and the components, and started to test it on my bench, very similar to OP’s experience, the motor started to spin and the controller is working now. I rigged it to the van with the motor/controller + burner without the heat exchanger and it does ignite and create flame. I will need new gaskets to put everything together. I think I will just run it like this without potting the controller to see what will happen.

The BTS247Z is a N-channel FET device with two temperature sensor outputs, pin2 and pin4, pin1 is the Gate of the FET which should get control voltage from the microcontroller, probably thru a buffer stage. The slanted part on my board has different marking, 422 U3D, it is a Vishay rectifier, basically a diode.

Here are a couple of pictures, I was able to taker out the PCB without opening the back of the controller housing.

8A53BE53-E4D6-41EE-8349-65155EC5FD83.jpeg
2AC9F4A4-D90C-414C-BAFA-7BFF4CF8B49E.jpeg
 

rollerbearing

Well-known member
Great job depotting!!

So - to be clear - you have not reflowed any solder yet? It just began working after depotting?

Any thoughts regarding how it is detecting the motor current? By Vishay slanted device do you mean that big black barrel rectifier with the white cathode band?
 
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DIYRV2020

Active member
Great job depotting!!

So - to be clear - you have not reflowed any solder yet? It just began working after depotting?

Any thoughts regarding how it is detecting the motor current? By Vishay slanted device do you mean that big black barrel rectifier with the white cathode band?
Well I did check continuity of the two connector pins that go to the motor, the pin that connects to the pin5 of BTS247Z seemed to have intermittent connection but I am not 100% sure since there is still some potting material on the pins of the FET, and I didn’t fix the board in place so the way I probed it was kind of whacky. I did use solder iron to heat up and add some solder to that pin on the back side of the board. I also used heat gun to reflow the BTS247Z but that was after the controller was working, just as some additional insurance.

The slanted part I talked about is the one on the back side connected across the two motor power pins, the rectangular one. The marking on the part on OP‘s board is W909U I believe.
 

rollerbearing

Well-known member
I've used a lot of Vishay precision resistors as shunts - was just wondering if that might have been it. But across the motor pins it does sound like an inductive back emf protection diode.
 

DIYRV2020

Active member
I've used a lot of Vishay precision resistors as shunts - was just wondering if that might have been it. But across the motor pins it does sound like an inductive back emf protection diode.
I think for current detection a very small value precision resistor in serial would make more sense. The BTS247Z has two temp sensors built in, maybe the sensor outputs can be used to figure out the current since temperature should correlate with supply current. Just my guess.
 

lnal

New member
Our 2007 d5wz seems dead. The fan did spin with 9v batter. our van only has a aux heat button. Would love to replace with something we can control manually to preheat. Looks like cheap ones are under 250$ now…. ?
 

drew502

Member
Our 2007 d5wz seems dead. The fan did spin with 9v batter. our van only has a aux heat button. Would love to replace with something we can control manually to preheat. Looks like cheap ones are under 250$ now…. ?
Out of curiosity - where did you find the units for $250?
 

drew502

Member
markxengineering said:
It's dead again! I'm waving the white flag, it was fun to troubleshoot but now I want it to work. In looking for a replacement ECU, I came across this one
https://heaters4you.com/eberspacher...001.html?search_query=control+unit&results=66
Advertised for Mercedes Vito, not Sprinter, but it is a D5WZ. Anyone know if that would work? I'll do some calling around tomorrow.

Anyone ever able to determine if the ECU in the above link will work with a Sprinter Espar D5WZ?
 

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