I have a 1987 300D that has been blowing fuse #7. The items listed on the fuse box cover for this fuse are: backup lamp, heating water valve, water pump, engine fan, heating system for washer jets, climate control system, relay auxillary fan term. 86, aut. transmission electrics, blower motor inside temperature sensor, air condition compressor.

The thing I'm worried about is that the water pump is on this list. Is my water pump not working now that this fuse is blown? That sounds like a very bad thing. But my temp guage never goes higher than normal. The main engine fan seems to be engaged. It obviously affects the heater water valve, because I now have hot air blowing out of my defrost vents all the time. Should I even be driving the car?

Any ideas on where to start troubleshooting? I already disconnected the dashboard heating control unit, and this did not solve the problem.

Thanks!

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1987 Mercedes 300D ~200K (Greasecar & Biodiesel)
1993 Ford F-250 7.3 IDI diesel 165K (Biodiesel)
1996 Thomas/International Bus with DT466 engine