hi.. i have a question do anyone know where the a/c fan blower regulator is located on a 1986 mercedes 300e my a/c only works on low speed thanks for the help.

The blower regulator should be located under the blower motor. Both are located under the wiper assembly on the fire-wall. If you do the job yourself, be careful when removing the wiper assembly. There are a couple of mounting bolts that are a little bit hidden up under the bottom of the windshield. They are not hard to get to, just hard to see. When you remove the wiper assembly it will pull out easily, it does not need to be forced.

And there are little tang clips that hold the top half of the blower housing to the lower half.

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Thanks, Nels
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86 300E
93 W250 4X4 Cummins Power
72 F250 Highboy
89 S-10 408ci BBC
custom V Four Chopper
77 Peterbilt 352
83 Jeep CJ-5

Before digging down to the blower, I would do a simple regulator trigger voltage test.
At the firewall . behind brake booster, is the blower 3 wire feed plug. [red/yl/blk]The yellow wire feeds a variable voltage from the Control Panel to the regulator. This is how they control the speed. So, voltage across yl/blk at this connector should be variable from approx. 2-9 V. , depending on CP setting. Voltage across red/blk is 12v.at all settings. If OK, then your problem is down at the motor/reg. and the next test requires digging down there.
The test there is to jumper a wire from the blu wire of motor to ground w/key ON...that will result in HIGH blower..if blower is still slow/dragging, then the problem is dry/worn bearings or bad brushes in motor. If OK w/jumper of blu wire , then regulator is bad.[ this jumper test simply takes the reg out of the circuit..ie..by-passes reg. ]. The Red + 12V. at blower is always hot, so, as you can see, the switching of the blower is done on the ground side..ie, blu wire... [switched ground].....
These sequenced test steps will diagnose the culprit w/o guesswork.

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A Dalton

I have a question about these blower regulators. I understard it's a electronic circuit. My 1992 500SEL has bad regulator. I bought a replacment but this new one get hot rapidly. And after half minute of succesful operation, it stopped working. Thats when I realised that the regulater was VERY HOT. After cooling I re-tried to use it and it seemed to be working but again, getting hot within seconds. I did not wait took it to extreme this time.
The question is , Is this normal for this regulator to get very hot (cannot even touch it).? I don't think my blower is bad. It's blowing air good. The fuse is 5A does not blow off, indication that the currents are within limit. There is heat sink on the regulator, but not sure if that's doing the job well.

Satjosh