87 300d no blower motor, wiring problem ? - PeachParts Mercedes-Benz Forum

mickeyd · #1 06-28-2006, 09:41 PM

87 300d blower motor stopped working, did the norm, ck fuses and relays , all ok. next i dug down to blower motor, red wire had power to and blue wire had power from. i took motor out since i was there,cleaned brushes , lubed end bearings, bench test worked great , reinstall in car and try, nothing ! i proceeded to interior and changed push button control with a known good one, still nothing ! went back to motor ck for power again, ok, red live going in blue live coming out, followed harness to fire wall, there was a 3 plug connector on top of firewall, blk , red ,yellow, in color. i disconnected the plug and tested at firewall, red had power ,other two nothing, in testing that connector i hit the blk wire with test light while testing the red. at that moment i heard a small pop like a fuse popping, red wire now has no power, ck all fuses on left front inner fender all ok, don,t know where to go from here "? is there fuses else where ? where does power to red wire come from? please help if you can thank you mike d

87 300d
79 300d
80 560sel
85 560sel euro
86 500sec euro
84 380 parts car
96 lincoln town car p.o.s.

Jeremy5848 · #2 06-29-2006, 01:40 AM

I was going to suggest trying the Defrost switch setting, as that one always runs the fan at its highest speed. If that doesn't make the fan work then there is something wrong with the ACC or the power to it.

But reading on through your post and learning of the "pop," you need to solve that first and I don't know the 1987 electrical system. Maybe someone else will step in with information on where that plug goes and where other fuses might be in your car.

The electrical diagram I got off of Skinnerbox did not scan well and it is essentially illegible. The wires from the fan should go to the fan speed switches that are part of the ACC. If that part of the ACC is bad then the fan won't work at all.

Jeremy

dieseldiehard · #3 06-29-2006, 01:24 PM

the blower normall has a strip fuse inside a small black plastic elongated "box" about 2 inches long. Mounted on the L fenderwell near the shock towers as I recall. I can take pic if you need one.
There is also a speed regulator ie controller that may have blown. It's a triangular shaped module mounted at the fan housing at the firewall.
I don't know about troubleshooting it, it has a bunch of solid state in it. Most shops use a test module and by substitution find out if its bad. Having a parts car to get test modules from is the cheapest way to go in a situation like this, if you bought a new speed controller and it turned out not the problem you are stuck with it beca seu electrical items are generally not returnable.
Find the fuse first then take it from there. The climate control pushbutton unit iis different in the diesels, I have p/n 1248301885. Don't buy one from a gasser and expect it to work properly, but the fan might run ok if you swapped the gasser module in just the vacuum pods may not be the same, so flaps won't work properly O/W the fan ought to run on and off if you did use a temporary test module in your car from another donor vehicle. YMMV

mickeyd · #4 06-29-2006, 06:15 PM

hi, thank you for help , i found the fuse in line ,and it was blown . replaced it continued testing,found power coming out of 3 prong connector (red wire) goes it blower motor (red wire) comes out of blower motor (blue wire) into blower regulator pn a1248202710 , then i get nothing coming out of regulator, but if i ground blue wire , blower works .i,m thinking the regulator is bad , (any way to test ? )

dieseldiehard · #5 06-29-2006, 10:06 PM

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=8024143048

mickeyd · #6 07-06-2006, 06:30 PM

thanks for the great e bay site you directed me to , i saved 200.00 , instead of buying from mb dealer, it cured problem, everything is working great !