I have just bought a 1988 300e. In order to pass a safty check in Ontario the car must have air blown onto the front window. In my car the blower will not run. I have a manual on order but its not here yet. This is what I have done so far.
I checked the sampler motor and it sort of holds the paper to the intake hole. I have to put the paper on it just right for it to stay, but it does. I then went to the plug where the regulator plugs into the fire wall. The black ground is good when checked with a meter, the red larger red wire shows the battery value, the yellow wire shows between 5.8 and 8.5 volts with the control set to A/C on high, fan has been set to all settings. From what I have read is that if you have these readings it is the regulator or motor that is not working.
I removed the blower and and put and put 12 volts to it and it works well I think.(I was just holding it in my hand and it tried to fly away amd bit my thumb, don't do what I did, test it in its cradle.)
I put the meter onto the regulater output wires, the red and blue ones and got the battery output of 13 volts. The blower will not run.
I took a reading at the blower fuse( on left fender infront of main fuse box) and got battery output of 13 volts. This fuse was blown when I got the car so I have changed it. When I checked this with the test light it would not light. The light will not work from the regulater also.
Can anyone tell me why I seem to have the correct readings from these points but no power. I would like to try to get this working before sending it to a shop. Also is there a thread for removing the section of dash with heater controls on it. I got the window control section and the ash try part and the glove box but the heater part has me stopped. The wire from the blower comes out through the firewall goes to the fuse and back through the firewall and I was tring to track this wire down.
Thanks.
Lance.

The blower uses a switched ground from the regulator to complete the circuit.
Ground the blue wire from reg to ground and fan should run..
if it runs, reg is bad, if not , you have no power to blower live side........

What you say sounds good and I will give it a try, but can you or anyone tell me if I should have power to the blower fuse because there is no current there. The test light will not go on. So do you think if I check the ground at the motor it will make any power to this fuse.

NO
There should be power at the blower at all times , the Reg simply switches the blower to ground, so if you have no power at the fuse , you have no power at the blower ..
Check the connections at the fuse and look for hair-line cracks..if not , start chasing the feed wire to the fuse connectors........do you have the exterior fuse .. there was a change from the fuse box on later models..??

Thanks I guess I will wait to get the manual. I was thinking the fuse box is the blower fuse box but I just don't know. It had a flat metel fuse thats held in with two screws. The old fuse was toast. Its in a little black plastic holder with a fold over snap lid.

The Exterior fuse was added after serial # F023505

All they did was to put a fuse outside of the box and wire it in parallel to fuse # 12 in the fuse box..
See if there is a fuse in #12..if there is , you have the earlier style..
Key on, of course, when testing
Some of these were also converted by the owners , in which case you want to look at the wires under fuse # 12 for bad connectors..

The fuse at 12 is not in use, On the fuse cover is shows 12 and 13? as unused. On the last line of the fuse ID it says "blower fuse in outside box.
The outside fuse has only one heavy wire that comes from the fire wall and then returns through the fire wall to some thing unknown. I will wait for manual so I don't bust or blow some thing up.

The manual should do it ..
..only thing that is strange to me [looking here at the schematic] , is that you state you have 12v power at the firewall plug/red .. that is after the fuse and feeds directly to reg/blower 12v feed ... so, i would still suspect reg and verify by grounding blue wire .. or just see if you have power at blower red wire and ground..
Good Lick

I guess the trouble with a multi meter is it says there is volts but not current.
Like I said at the fuse the meter says 13.2 volts but not enough power to light test light. Looks like a ice pic with a ground wire and a light bulb. So I will wait to find out how to pull part of dash to trace the wire. Wish I could just send it to dealer but can't bring myself to do that..........yet.

If you read good voltage at a point, and have a good ground, but yet it wont power anything, that means that their is a "high impedance" (resistance) "upstream" of where you are measuring it. Basically a loose connection, bad crimp etc. Basically there is enough current getting through to power the meter (since it doesn't use any power from what it is measuring) but not enough can get through to power anything. This is just general advice that may or may not apply to what you are doing. Another way to verify this (and a good test to always do in these situations) is to measure the voltage with the load CONNECTED. You will probably see it then go to 0. This is your hint to go look for a bad connection somewhere.

Mike

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

The regulator is a switching device, voltage controlled, that switchs the ground at the blower motor on and off continuously, so that fan speed is determined by on duty cycle. You will need a duty cycle meter or oscilliscope to check it.

However, if you do NOT have power at the output side of the strip fuse, you have a wiring problem. Must have 12V on both sides.

If the blower runs with 12 V applied and proper ground, your problem is in the control circuit. This could be bad wiring (do you have 12V at the plug to the motor?) or the regulator gone south (expensive).

Also, make sure you don't have something in the heater box locking the fan cages up -- this will blow the fuse.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

You know when I looked at the fuse it looked like it took a long time to go not fast like a short. I think you are correct about the bad ground. The fuse went on a slow burn lots of heat enough to discolour the screw and sag the plastic. I had a melted headlight socket as well from what I think was a poor ground. Will do as you suggest and look for ground. Has to be a fare size I would think.

I read that you have voltage, but no current. That is correct. In order for you to have current anywhere, your blower motor would have to be working or a direct short somewhere. Always check for voltage first, then when you get your regulator replaced then you can check for correct current. Your regulator is open and so you will have no current. You have to have a complete circuit to have any current. To test reg you just jumper a good ground to the output side of the reg. If it then works replace reg, if not then replace blower. It is a good idea to get an amp draw once the motor is up and running.
Hope this helps JohnT

Thanks for the help but I gave up and will tow the car to a shop for the fix.
I think is wireing trouble. tried to trace wire to find out why no power. Oh my God what a pile of wire. I will stick to fooling with the big parts and leave the under dash stuff to those who know.
Thanks again.
Lance.