VW T4 111kW AHY, auxiliary heater defective (Solution)

Hello, I own a VW T4 from 4/1999 with the engine code AHY.

The factory-installed Eberspächer D4WS water heater has recently stopped working. When turned on, the water circulation pump runs and warms the interior using residual engine heat, but that's all.
The control panel of the standby heater isn't flashing either, which would normally indicate an error code. The circulation pump of the standby heater is receiving power on one cable but not on the other. It should be cycling on and off.

When the pump is directly powered, it clicks briefly. The fuses related to the battery are all fine, those located on the left side under the steering wheel compartment are okay, and those under the driver's seat are also good.
Reading the climate control system data reveals an intermittent fault with the fan motor. The error has been cleared/deleted. Bypassing the temperature sensor located under the towing hook with a test lamp also doesn't resolve the issue. Does anyone have any ideas?

[Translating...]

Hallo,

Fehlerspeicher der Standheizung Auslesen... geht entweder mit VCDS oder direkt mit dem Eberspächer Tool. https://community.dieselschrauber.org/en/viewtopic.php?t=26145

Viele Grüße, Rainer

Rainer is an Eberspächer .
You can read this information using the EasyStartR+ remote control if you have one.

Does the fuel pump at least make a sound for a short time at the beginning, or not at all?

Quote:

Rainer is an Eberspächer

.
Corrected.

Okay, I've made some progress now. I was able to read the display using a key combination. No errors were found, but the battery under the seat for the auxiliary heater had only 0.74 volts. So, I replaced it. Now the ventilation system turns on, and various relays and pumps are working, but the fuel pump isn't ticking. Therefore, no fuel is reaching the engine.

Okay, so I expanded it, connected an external hose to the pump's suction line and filled it with fuel, then briefly energized it repeatedly. Nothing is coming out of the pressure line. Is this pump actually drawing fuel properly from the tank?
If I disconnect the fuel line, no fuel will leak out of it.

The pump first draws in the fuel and then pushes it forward.
I would try taking it apart and cleaning the strainer inside.

Servus Se6!

sebv6 wrote:

... The circulation pump for the underfloor heating receives power on one cable, but not on the other.

versus

sebv6 wrote:

... die batterie unterm sitz für die standheizung hatte 0.74volt. ...

With a voltage of only 0.74V at the second battery, the dosing pump could never have had enough power to operate.
You should provide us with some more specific information here, otherwise we will just be aimlessly searching around the area .
Describe in detail, step by step, what the auxiliary heater does after it has been turned on!
First, the burner fan and circulation pump must start up for a function test. Then, turn off the fan and turn on the glow plug; the latter can be detected by a voltage drop at the (secondary) battery. After approximately 10 seconds, the dosing pump will THEN begin to cycle.
Is everything as I described it?
For example, if a blockage or defect in the burner fan is detected, the process will be stopped *before* that point, and the pump will never receive power – intentionally.

"I would start by addressing that issue first, rather than disconnecting any hoses where it wouldn't be a problem if the dosing pump from the main system isn't activated ."

By the way, there must be a reason why the second battery was so deeply discharged. We need to investigate and fix this issue as well!

Best regards from Munich!

sebv6 wrote:

die Batterie unterm Sitz für die Standheizung hatte 0.74volt.

Ah, the first classic maintenance bottleneck .

RedR32 wrote:

sebv6 wrote: die Batterie unterm Sitz für die Standheizung hatte 0.74volt. Ah, the first classic maintenance bottleneck

.

Good saying

Wenn der Temperaturschalter in der Gegend der Abschleppöse überbrückt ist, sollte die Heizung anlaufen, wenn der Motor läuft (Zuheizerfunktion). MacDid she do it?

This way, you can at least rule out dead batteries as a possible cause.

One thing I would definitely do with this auxiliary heater is replace the flame arrestor screen, if it's a replaceable type.
She must be around that age.
And be sure to replace the heating element with a ceramic one.
With those two things, you've already addressed the main sources of problems with these auxiliary heaters.
"On my friend's ACV with the D3WZ engine, I only replaced the glow plug because the flame arrester is permanently integrated. Since then, she hasn't had any more starting problems, even though the flame arrester looks pretty bad."
Or if you're already at it, maybe consider swapping it for a refurbished D5WS or D5WZ.
I already find the D4 to be too weak, especially since they removed the two-way valve that short-circuits the small heating circuit, which is how the motor helps with heating during auxiliary heating operation.

Today, I finally had some time to dedicate to this topic.
Die Dosierpumpe habe ich erneuert und die 2. Battery.
After manually turning on the WSH, the fan inside it should start running.
that blows air into the combustion chamber.

"But nothing is happening. I disassembled the J162 control unit and checked it for water damage."
checked, as well as all fuses and other safety devices.

I think I need to expand the WSH (presumably a software or system) in order to test the fan.

Okay, after a long search: The error code indicated a faulty glow plug. I removed the heater and took it to the Bosch service center. They found that the control unit also had water damage and was defective. So, I got a new auxiliary heater, installed it. Unfortunately, it still didn't work. After a Saturday spent at the Bosch service center, where we searched together, I found a broken cable near the coolant circulation area under the expansion tank. Now, finally, it works! Conclusion: Glow plug: approximately 30 Euros, auxiliary heater: approximately 300 Euros, dosing pump: 80 Euros, labor costs at the Bosch service center: 100 Euros (business partner), battery under the seat: 80 Euros, gray hairs: 101.

Thank you for the feedback .