appatula

I got fed up with queeky noises comming from inside my dash and shelled out some cash for a new OEM Bosch motor. Before the replacement, on cold days the blower (when on high fan speed selection) would not operate until I turned the car off and back on. I was thinking that the heated engine bay made it work magically after a restart because the bushings were so incredibly shot Last night I put the brand new motor in and fired up the heat, a different but similar event happened. About 30 seconds after I hit the CC button the motor kicks in and works like normal. I don't understand why it has a thirty second lag, note that I am not on "AUTO" rather high speed fan selection which should fire the motor up immediately. Blower motor regulator? Ignition switch? Faulty fuse connection? Can any of you point me into a good direction? Thanks guys

vanwiek

I just went out and tested mine and with the fan switch set to high, the engine has barely started before the fan is running full blast. My money is on the regulator.

appatula

Yeah I was thinking the same thing, however, I hate just throwing parts at issues. Any way to test a regulator with DMM or oscilliscope etc.?

vanwiek

I couldn't find a test in the service manual that seemed applicable to this problem.

appatula

I'll take a look in my Mitchell Service Manual and see if I can find anything there, thanks for looking vanwiek!

White_Knuckles

Never spotted a way to test the regulator but there is a method to test and rule out the climate control which is also suspicious.

The regulator is a solid state device that drops working current to the motor (low speed) by converting the current to heat. It has large fins (heat-sink) and is mounted with that white goo - thermal compound. It may indeed create strange behavior.

It receives voltage level inputs from the CC. I found a test that gives you average voltage levels the dash unit (CC) sends for low and high modes. This will tell you if the CC is working okay. To test, you disconnect a three prong connector hiding behind the brake vacuum booster, drivers side.

Meter reading the connector output you can tell what the regulator "sees" for input. Something like: 9 volts DC (read from the connector pin to ground) on low is normal. A 3V reading means you've selected high. You test selecting different speeds and turning the key on.

With the CC ruled out, all that's left is Mr. regulator as there's nothing else in the circuit. You cannot bypass the input and "jumper" the motor into high by poking a 12V source into the connector. The motor is connected directly to the regulator's output side.

It's not something simple as reading the regulator's output to test it. It may show 12V when the fan's on high but actually it's dropping current into heat and the motor barely creeps. Solid state devices use current limiting not voltage. Maybe DC amperage readings could be used to test.

Some frustrated owners have hot wired the blower motor with a remote dash switch and tossed the regulator. Slow and medium speeds could be selected using an old school resistor array robbed from an American car. Mounting the Ford fan switch might be a trick. New regulators are spendy, snag one from a bone yard.

appatula

Whiteknuckles, great writeup!! I'll look into measuring current after the regulator, however, after having to cowl apart 5 times I really am dreading doing it again. I'll try to rule out the climate control, I believe I have tested the climate control output pins before via the service manual and everything looked normal. I'm leaning toward the regulator and or a faulty connection. I'm also considering adding a variable current limiting resistor for infinite adjustment and ditching the high and low push buttons, how would you go about this? I'll have to dig out the wiring diagrams and start drawing something up after work. Thanks again for the in-depth lesson, information like that is getting harder and harder to come by

White_Knuckles

I'd go with the CC retest if you're uncertain. You may perform voltage testing l on the regulator output to verify if low creates a drop. I've never seen anything on reg. output to motor tests. Seems they just swap them out. My reg. took a slow death running the blower at half of what it should on high and almost nothing felt at the vents on low.

Should you decide to change out the speed control, you would need a resistor pack out of some other make. The packs are large ceramic resistors sometimes mounted in a metal cage as they get hot. The fan selector switch selects them in series adding the most drop for low. It's hard to guess the current load the MB blower will pull and could smoke them. I'd hunt for a truck with a large blower. The factory fan selector switch (usually rotary) might be electrically copied on a rated three-pole,bat-handle type to keep a clean profile. That would be off - low - high.

A variable resistor would be huge! That bad boy would have to be rated at 20A, ceramic, wire-wound with a 2" diameter. The thing could flame your console and "off" requires another switch. Your back to solid state here where a variable resistor controls a remote regulator device.

appatula

Yeah, now that I think of it your absolutely right. Maybe a PWM driver would be a better hi-tek solution I have now narrowed down what triggers the blower motor now....a flick of the right blinker....very weird...combination relay malfunction?

neanderthal

what temp is the CC set to.

im of the opinion that the fan doesnt blow until it can nearly blow the desired temp. i noticed that on my car (always on auto, 75 degrees, EC in winter) that it would wait for about a minute when i started the car in the winter. so whenit did blow, it was blowing somewhat warm air.
in my brothers camry, its a fan with a temperature section, and it blows when its on, regardless of what its set to.

on my car, it blows cold right away if the AC is on.

food for thought.

appatula

The CC is usually set to 22C to MAX, never on AUTO for fan speed. Before my old motor went, this problem slowly snuck up and became evident but before the motor would start instantaneously upon pushing the BI-LEVEL button on hi fan speed (MAX temp). It does weird things, like after a 20 mile drive I'll shut the car off and turn it back on and BOOM! It works! Or drive 3 miles hit my right blinker and BOOM! It works! At this point I'm thinking contacts or a faulty combo relay, I'll have to look to see if the relay is part of the blower circuit in any way....if not then the regulator is the only other thing I can really think of.

vanwiek

Looking at the diagrams I can't see how those two are related. It will be very interesting to find out.

White_Knuckles

Yeah bro, no "combo" or dedicated relay in the blower circuit. She's CC to regulator. Regulator to motor. The only thing unique is the 30A strip fuse externally mounted outside the main fuse box.

The signal is strange as not even related. Retest to duplicate.

appatula

Yeah, I confirmed this after looking over the schemas in the Mitchell manual. I feel as if this is one of those problems that you have to "throw" parts at . CC tested out, no problems . I'll keep you all posted..........

appatula

More electrical problems are popping up.......sitting in traffic last night with the blower on HI at a stop when idling the headlights started pulsating, thus dimming and then getting bright. The blower also slowed and sped up in syn with the headlight pulsating. This morning the right blinker activated the blower again....works like a charm! Would I be safe to add the voltage regulator to my list of parts with these symptoms?

appatula

Ahh......here I am complaining again This morning was in the teens, thus very very cold. So I warmed it up, the usual procedure is that the blower will not spin until the car is warm and I kill it and start it back up. Tried this today and nothing I would have toughed the cold out but the windshield was just icing up like crazy on the inside. I decided to let it warm up past the usual 15 min in hopes of success, 45min later I hop in and the motor is blowing! Then at a stoplight I noticed the recirculation switch was lit and no matter which way I pushed it, it would not turn off. So I just killed it and started it back up at the light....good to go!

Therefore I now believe this problem to be temperature dependent, from any of your guys experience/expertise what part in the blower circuit would be consistently faulty only during cold weather and progressively get worst in even colder weather? I hope this is not annoying you guys, I just have a BIG pet peeve about throwing parts at an issue without having a pretty solid idea of what is actually wrong because with my luck its never the "winning" part and my wallet ends up not talking to me for the next couple of days

Thanks ahead of time guys!

appatula

Friggen thing completely quit on me about 4 days ago. I picked up a blower motor regulator and put it in today and it didn't change a thing . We have a decent snow storm heading towards CT as I type this so I added an auxiliary 12V switched wire to control the motor for the time being . I'm going to rip apart the CC unit and see if I can spot and cold solder joints or anything out of the ordinary. If anyone has any advice it will be greatly appreciated. Also if anyone is willing to help a fellow forum member out and part with an extra CC unit I would be so very happy. Love how these things happen at the worst possible time!! Above all else, I'll drive my 300E with the windows down in 20 degree weather for the time being, because it's worth it.