Eberspacher Control unit and cooked Diode.

Lee D

In the best of engineering traditions, replace it and see what else blows up! (and yes, diodes do have a finite life)

Cheers

Peter

bollocks. ;-) Only a VERY VERY poorly specced diode has a finite life. Steve

Or, more accurately, they are specced *to* have a optimal lifetime aginst cost, the good old "bathtub" curve for component reliability.

Richard

Whilst they have no moving parts, they are still subject to wear and tear from a variety of sources.

They can fail due any number of reasons and it's not just a poor specification. It could be a manufacturing defect, spikes (EMI), reverse voltages, temperature (heating cooling etc.), humidity, vibration (especially in a LR!)

If you look at Mil HDBK 217F you will find a mean time between failures for diodes. It may be high, but it is finite! :-)

Cheers

Peter

Lucky me! looks like I got several poorly speced items and now looking out for a control unit.

When plugged back in the fuel pump kicked in straight away, then I thought what the hell and switched it all on.. Fired up a treat and got nice and toasty. The themo stat worked I could see the relay operating to shut the cuircut down or at least the petrol side.. the heater carried on heating regardless. I switched it all off and if still carried on regardless. I disconnected it (last resort!) and it stopped.. now ideal as they should run to burn off any fuel

So renewed appeal to liberate any old B4L controllers sat on a shelf anywhere.

:-(

Lee D

Whilst they have no moving parts, they are still subject to wear and tear from a variety of sources.

They can fail due any number of reasons and it's not just a poor specification. It could be a manufacturing defect, spikes (EMI), reverse voltages, temperature (heating cooling etc.), humidity, vibration (especially in a LR!)

If you look at Mil HDBK 217F you will find a mean time between failures for diodes. It may be high, but it is finite! :-)

Cheers

Peter

Oh sure, if you abuse them they fail, which gives anything a finite life. You imply that they fail by some internal mechanism, like a lead acid battery HAS a finite life, however you treat it. Kept within specs, diodes won't fail.

Steve

Lee_D wrote: The themo stat worked I could see the relay operating to shut the

So, did the fuel pump cut out or not ! It sounds like the relay contacts have welded - I have seen cases where the armatures move, fooling you into thinking the contacts are following it.

Bung it up here and I'll take a look at it for you, unless some kind soul has spares.

Steve

Fuel pump wasn't having issues before the Diode replacement, the issue was no hot air at all and the cool fan coming on when it liked... even when away from the truck.

I replaced the diode with what the local chap sold me, same part number etc and inserted the right way.

Now as soon as it's plugged in the fuel pump kicked in. The metering pump fired up as it is supposed to when the switch was pulled to position II. When the switch is pushed back in both the fuel and metering pumps carry on until the leads are pulled from the unit.

I suspect theres more to it than just the diode, the new one is getting hot too so no doubt summat else is duff but it's all a bit over my current level of understanding.

The heater worked fine until recently. I suspect the moisture in the cabin from the leaking roof has reaked havoc with the circuit. Leak is now fixed, thats about as positive as it gets. I'll explore some more options but may yet drop it off for you to prod. Does your heater work? Just wondering how you would bench test it.

Lee

Lee_D uttered summat worrerz funny about:

oh yep knew there was summat else, the relays seem to be moving ok and not welded.

dammed frustrating.

Lee

Simulate all the pumps and sensors on the bench. Don't know if my hairyscratcher works or not.

Steve