FBH problem
 

Well, having only quite recently fitted an FBH to my facelift 75, and everything working great for a few weeks it would seem to have developed a problem.

I have a temp gauge fitted to my car so I can see what's happening quite easily. Normally when the FBH fires up I can see the temp climbs quite quickly up to about 75 Deg, which is of course where the FBH would back off. I noticed the other day that the temp climbed quickly to about 40 Deg then slow right down. I figured the FBH had turned off for some reason, maybe the outside temp had gone up a little.

Anyway, it was cold outside this morning, so I thought I would try it again. The same thing happened, it was obviously working up to about 60 deg then turned off. I pulled up and let the car tick over for a few minutes. The temp gauge started to drop a few degrees, so I opened the bonnet and felt the FBH exhaust. It was just warm, and the FBH had turned off.

I went home and let the car cool down for about an hour. By this time the outside temp had gone up so I wired +12 to pin one (it's an early 66232C) and set my stopwatch going. It made a few noises, started to get warm (exhaust pipe) and ran for a total of about 3 mins before totally shutting down. I removed the fuse to reset and tried again, same thing! total shutdown at about 3 mins.

Does anyone know what the problem could be? The most annoying thing is I have just ordered a GSM unit to trigger it by text.:(

Do you have the blowers on ?
I’ve noticed that if blower demand is high, it saps the heat generated by the FBH and so the temperature drops. This is more pronounced if you’re parked

I thought of that, so I lowered the temp. The temp gauge still dropped so I jumped out and lifted the bonnet to check. The FBH wasn't running anymore, the exhaust pipe was cool enough to be able to grab hold of it.

Your Webasto has a PCB fault, glow plug/flame sensor fault, or dose pump fault. At full load the dose pump pulses 140PPM. and should pump 12ml+/m. Remove FBH fuse, unplug 2 pin plug and 6 pin plug. Inset a paper clip into pin 6 pin of the 6 pin plug, being careful not to misalign the pin receiver, with a wire attached long enough to reach the battery. Remove fuel line from FBH and insert into small receptacle. Tap the wire to battery 140 times at a rate of 2 taps per second, or 140 times in a minute, and measure the diesel delivered through the FBH fuel line, if ok.

You will need to have your PCB bench tested, if it starts ok, if still has start fault.

You Will need your glow plug bench tested, resistance test at 18- 30°C should read 0.2 to 0.3Ω blah blah, yeh right, took from a shelf at Webasto, ok as a guideline, they can work as high as 0.9Ω. If you are at this stage, FBH may as well have a de coke and new gasket, water pump impeller cleaned and a new O ring, and the burner mesh inspected.

Unfortunate it developed the fault so soon after you fitted it, sh and it happens

Hi , just to wind me up even more, the gsm unit arrived today. Yes, I realised I needed a relay for the fbh output. As it happens I will be using the 5 min delay in the gsm anyway.

The dosing pump is brand new, not to say it isn't faulty of course. Do you do fbh repairs?

Looks like I need to send it somewhere lol

Mike

For those who may be interested, I appear to have found the fault with my FBH.

I had a bit of time to play about with it this morning and it looks like I may have an intermittent fault with the water pump attached to the side of it.

When testing it this morning, it fired up and ran for approximately 5 mins before going totally silent. This didn't seem to tally with any of the timings that French Mike has posted on the internet. I had a good look around it, proding and poking when I noticed that the water outlet pipe was extremely hot. I started the engine and it immediately cooled down. I then turned off the engine and fired up the FBH again, the outlet pipe was getting hot again so I tapped the water pump and heard a bit of gurgling. I started the engine to help with the water flow and the FBH continued to run until the engine was up to 72 degs (maybe 15 mins). I switched off the engine and the heater carried on running till the temp was 74 then shut itself down.

So, I feel marginally better now as I know the problem is nothing too serious. I can remove the pump and strip it down, maybe even fit a new one.

My GSM unit arrived yesterday so I can now make a start on fitting that too.

So, if I can offer any advice to anyone, check water is actually flowing through your heater if it shuts down too early. Without flowing coolant, the heater will think it's done it's job by getting the water up to 74 Deg. It has in a sense, but only a very small amount.

Thanks for listening to my ramblings. ;)

Mike,if water is not circulating through the FBH then surelyit cannot circulate around your engine.imho.

Hi, that was my point, without the engine running it was totally reliant on the heaters pump so if the pump didn't run the water was going nowhere. This would cause a small amount of water to get hot very quickly. This would trick the heater into thinking the whole engine was up to temp when it wasn't. It then switched itself off.

When I tapped the pump and with the circulation of the cars engine water pump it brought the engine temp up to 72 degs in about 15 mins while ticking over. That would never happen in a million years without the FBH working.

I switched off the engine and let the temp climb to 74 purely on fbh power, when it shut itself down as it should.

This would indicate that my FBH pump probably wasn't running when it should have been, and a tap on the side with a screwdriver started it. It can't be trusted anymore, so needs pulling off and looking at.