[Archived]

Got that infernal cover off the pump, turns out there are no connectors under there, they are in the wires clipped to the chassis above it. It did let me turn the pump shaft by hand, moved freely. Unplugged the two spade connector in the 12 v feed to the pump and connected to a 12 v battery charger, pump runs fine draws about 18 amps, nameplate says 20 amps.

Managed to find a Webasto service manual part number 699.745 dated 1/2004 on the web and downloaded it. It shows pin outs for the control module and wiring diagrams for the pump and heater. However of the two versions shown before and after 1993, neither matches up to the way my unit is wired, which looks factory (Liberty) by the neatness wire ties, and circuit number labels on some of the wires.

My unit has one (looks black) wire in the A plug, it is a ground wire. The relay shown in the photo is the same as many in the 2nd bay power panel so I swapped out one of the “non essential ones” Still no water pump operation. Testing with the relay out of the socket, I check for 12v to the red wire on the relay, the “feed” wire (“30” terminal) and it has 12.8 v with the control module B plug unplugged. However, when I plug the B plug into the module the voltage at the red wire drops to about 12. Hmmmm. I try jumpering 12V from the #4 terminal of the B plug (the main 12Vfeed wire for the Webasto) to the red wire on the relay socket. Put the relay back in the socket. Water pump operates as it is supposed to. Off when unit turned off, on when unit running.

I followed the red wire that has the wavering voltage and it disappears up into the underside of the floor through a hole with a bunch of other wires. Running up probably to some chase leading to bay2 maybe? Not sure how plugging in the B connector at the module changes the voltage at a 12v feed wire that comes from ???. That would only make sense if the “12V” on the wire somehow was routed through the module.

Any suggestions? Sound like a bad control module? For this upcoming trip, if I need the Webasto (hope not, I’m going to Phoenix!), I made up a little plug in jumper from B4 terminal to the relay 30 terminal and I’ll just run it that way temporarily.

[Craig]

As the old timer said, ”If it had teeth it would’ve bit me”. Turns out the whole problem was caused by a bad fuse. Note I say bad, not blown fuse. The rest of the story:

I contacted Liberty today to buy the circuit sheets for my coach. I had been miserly and avoiding buying these for years. They would have saved many hours of struggling with electrical issues in the past and maybe this time. The sheets verified the red wire in my prior post, which in hindsight is PLAINLY labeled “7” (here is where the “would have bit me” allusion applies) runs to fuse 7 in the coach electric bay. I check the fuse, same voltage both sides of the fuse through the little holes in the top. Then I look again, what is that brown color on the exposed part of the left spade of the fuse? I pull it out and the plastic is swollen on both faces overlying that spade terminal. Hmmmmm again. I get a new fuse stick it in the socket and everything works perfectly.

What happened? Maybe some contaminant got on the fuse terminal or the socket and prevented good contact, or the socket was loose, arcing occurred, some oxides formed and poor connection. Hence when I connected the B connector back at the Webasto control module one of whose wires which again in hindsight I see has the same “7” circuit in one of the terminals, the draw from the Webasto control module was enough to reveal the poor connection back at the fuse – seen yesterday by me as a voltage drop at the relay red (7) wire when I plugged in the B connector.

Photos of the offending fuse are below, as well as autopsy photos showing the innards of the rascal. The inside of the fuse plastic appears melted by the heat caused by the poor connection.

LESSONS LEARNED

OCCAM’S RAZOR

The simplest solution is usually the right one. Look, really look, at the simple stuff before you go tearing things apart trying to fix them. Fuses, relays, connectors, starting with those you can get to without taking things apart. I mean I was ready to rip apart the control module and solder in new electrolytic capacitors (even ordered a capacitor assortment on Amazon) and did research on replacement circulation pumps. A photo of the label from my pump is attached in case it helps someone who needs one in the future, though the thing looks like it will last 100 years.

EXPLORE YOUR COACHES INNARDS WHEN IT IS CONVENIENT

If you plan to do some or all of your own service work, do as Jon has implored previously and take every panel, cover, access plate, whatever off and see what’s behind it. This does several important things:

1. You learn what is back there.
2. You find out if there are any frozen/stripped or oddball fasteners that you don’t have a left handed Lithuanian 7 point driver bit for. Nothing against Lithuanians. The time to find this out is while you are in space dock, not out in deep space as Scotty would say.
3. When putting fasteners back in place on panels that are exposed to the elements, put a liberal coat of never seize on them so 5 years from now when you have to take it off “out there” in the wilderness, it will come off without breaking. Also consider tossing those infernal Phillips drive fasteners and putting in a hex head equivalent.
4. You might just see something about to break/rub through/fall off, etc. that you can fix.

INVEST IN DOCUMENTATION

If like me you did not get the manuals with the coach, don’t cheap out and fail to buy them. The $150 was well spent. Indeed after some conversation about what I was working on, Todd at Liberty even sent me (unsolicited) an extra page that had the actual WIRING DIAGRAM of the involved circuits for the Webasto. Lonestar pointed out at least once before he has never seen a wiring diagram from a Liberty. They do exist at least at the mother ship.

Thanks to all who offered help and suggestions on solving this mystery.

[Archived]

Nice job!

[joel]

I really like David’s attitude about starting with the simple stuff. As an avowed lazy bones individual I look for the low hanging fruit long before I get into the more complex and more difficult solutions.

Excellent job.

---

1999 XLV X-6872,  liberty #440

[Jim]

I was in the airplane biz for a short period of time while in HS and college. Our chief mechanic (who was fully rated in anything up to 12,500# and was an FAA designed examiner for everything too) was a WWII Navy aircraft mechanic stationed on carriers. He taught me quite a few things … one of which was if I didn’t know the exact solution … start with the easy, basic stuff first. RIP Fred Stroebel.