i recenty bought a 1982 300D (i owned a very similar car before) - anyhow, it appears that the heater fan just doesn't want to go on -- i can't even hear it struggling - - i don't think its the controls since if i have the engine off (but the electrical system on) i can hear things click over when i press the different climate control buttons, and a pump (i believe its the heater circulation pump) is functioning - - so it appears that the climate control is working ... but i might be wrong . . . anyhow, so i looked in the haynes manual to find the heat blower, and i did find it under the passenger dash - i saw that there is only one plug going to it . . . thus, i turned on the heat and then used a meter to see if there was any electrical output - i assume that this is a normal bipolar plug, so i put the positive test probe in one of the holes, and the negative test probe in the other connecter hole ... i tried both combinations, but either way i didn't get any indication of current - i might be assuming that this plug or the system works differently than i expect, however, i assume that if the heater should be on, there would be electricity going to the blower motor - maybe i tested it wrong . . . who knows . . . so, i suppose the blower motor could be the thing broken . . . . but i have a feeling that it is something else that either turns on the blower motor or a wire that's corrupt. . . so i guess my question is, what other tests can i do to trace this problem? it's starting to get colder outside . . . so the heat might be a useful function.

yestim,

Seems to me the blower motor has more than one speed, so I would assume the two leads are both positive and the blower motor is grounded somewhere. Try reading the Voltage level relative to ground, and then check the continuity of the motor connections. If they are both open when connected to ground, but connected (no resistance) to each other it would seem your original assumption would be correct. In that case I would run wires from the battery terminals to the motor to see if that makes it work. If there is continuity to ground from the plugs on the motor leads, then I would run the positive wire to the plugs to see if that makes the motor run. If the motor runs and the problem is in the wiring, check the fuse, and check it by taking it out and inspecting it then putting it back in (these fuses are pretty susceptible to corrosion and then popping but still looking ok from afar). If the fuse is ok and the problem seems to be in the control box, there are others on this board with direct experience re-soldering faulted connections on the box and one of them can get you aimed in the right direction. I have never taken one of these control boxes out. Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

I obtained some climate control diagnostic documentation from Larry Bible. It proved to be very helpful for my 1977 300D. Shoot me your fax number and I'll fax it over Monday morning
.

JCD:p

i finally hooked up with a fax number - so if its still possible, those climate control papers would be very helpful.

FAX = 630-985-3811

thanks
tim

Yestim,

I don't have them with me today. I'll try to remember to fax them to you tomorrow.

JCD

Yestim,

I had to go out of town last week and I left the diagnostic info at home.

I'll fax it next monday or tuesday

JCD

Tim,

Tried to fax to you yesterday and couldn't connect. Is your Fax still hooked up.

JCD