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Author Topic: Watch out for that blower switch, it could fry your car.  (Read 53339 times)
Jon Weywadt
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« on: August 14, 2010, 10:52:25 pm »

The other day I was driving back from my Dad's house with my daughter as passenger. It was pouring down rain and so the windscreen was beginning to fog up. I turned the blower on high and it ran for a few minutes. Soon I began to smell hot insulation and just as I realized it was coming from inside the car, smoke began to seep out of the dash around the switch. I immediately turned the blower off and kept my hand on the fire extinguisher, just in case. Fortunately the smoke dissipated and no fire erupted.

This just presses the urgency of the modification that Jan and I have been planning. We will install relays and fuses, so the blower gets its power through the relays and not the switch. The switch will only draw the current required to pull the relay, not the 15 amps that the blower draws on full power. Each power setting will have a relay and a fuse.

I hope you all will be paying attention to your own blower switches. I know others have modified this circuit. Perhaps yu can share what and how you did it. I will post photos on this post as the modification comes along.
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Anders Dinsen
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« Reply #1 on: August 15, 2010, 08:20:53 am »

I think this in an experience all Murena owners at some point will face. I have yet to face this problem, though Wink
Most people just replace the switch - and that's that. I think there was a report of someone here on the forum who fitted relays in the way you're planning, and it's probably a slightly better solution, especially if they're fitted close to the blower so the wiring could be shortened, but for originality and simplicity, you should be fine with a new switch plugged in.

Lennart did a photo series a few years ago documenting the replacement procedure:

http://www.matrasport.dk/Cars/Murena/Stories/fanswitch/index.html



/Anders

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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
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Oetker
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« Reply #2 on: August 17, 2010, 12:32:41 pm »

The switch lasted 30 years.
The problem occur when the blower motor is asking to much current for some time because of bad bearing.
The switch and wiring around it get overheated and finaly give up.
Since you already adressed the problem of the blower, yo should be fine with a new switch.

http://www.cbsonline.co.uk/3-speed-heater-fan-switch--swfan-1578-p.asp
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I feel like Jonah, only my fish looks different.
Murena 2.2 Red 1982. Murena 1.6 black on places.
Oetker
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« Reply #3 on: August 17, 2010, 11:05:54 pm »

Maybe this is a good solution if you plan electronic.
Give the new switch 3 resistors to replace the potmeter.

http://cgi.ebay.co.uk/12V-30A-DC-Motor-Speed-Control-PWM-HHO-RC-Controller-/170400933060?pt=LH_DefaultDomain_0

Edit:
Only 2 resistors are needed because full power doesn't need one.
« Last Edit: August 18, 2010, 04:07:53 pm by Oetker » Logged

I feel like Jonah, only my fish looks different.
Murena 2.2 Red 1982. Murena 1.6 black on places.
Jon Weywadt
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« Reply #4 on: August 18, 2010, 10:43:18 am »

Maybe this is a good solution if you plan electronic.
Give the new switch 3 resistors to replace the potmeter.
Hi Oetker.

That is a super solution. I just ordered one, since single speed fans are much easier (and cheaper) to find.

/Jon.
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brinkie
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« Reply #5 on: August 27, 2010, 02:13:10 pm »

Maybe this is a good solution if you plan electronic.
Give the new switch 3 resistors to replace the potmeter.

http://cgi.ebay.co.uk/12V-30A-DC-Motor-Speed-Control-PWM-HHO-RC-Controller-/170400933060?pt=LH_DefaultDomain_0

Edit:
Only 2 resistors are needed because full power doesn't need one.
Why not use a single potentiometer instead of the switch? It's a much smoother solution. You only have to source a potentiometer that has the same shaft size as the original switch (otherwise the knob won't fit). Then you will have stepless control of your fan. But fitting a couple of resistors will do the job as well and will keep the outside looking original Smiley

By the way, my switch was killed by moisture, corrosion and subsequent overheating due to a bad contact area (more resistance, P equals R times I squared...). I had exactly the same experience as the topic starter.




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/Robert

Previous owner of a Matra Murena 2.2 (1981)
JV
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« Reply #6 on: August 27, 2010, 05:57:28 pm »

Why not use a single potentiometer instead of the switch? It's a much smoother solution. You only have to source a potentiometer that has the same shaft size as the original switch (otherwise the knob won't fit). Then you will have stepless control of your fan. But fitting a couple of resistors will do the job as well and will keep the outside looking original Smiley

Much too intense currents for a normal potentiometer. And using some resistors may only seem interesting if you like an extra heating in your dashboard, I'm afraid.
« Last Edit: August 29, 2010, 08:33:08 am by JV » Logged

Jan Verdam
Jon Weywadt
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« Reply #7 on: August 31, 2010, 10:36:16 pm »

Well. Since finding a new motor turned out to be a challenge, I took the old motor apart the other day to see if it could be salvaged. No such luck. One of the windings in the stator has overheated, probably shorted, which explains the smoke coming from the switch. Angry

But today I was in luck. I asked at a garrage, where they sent me to a salvage place (AHKA on Ole Romersvej 16, in 2630 Taastrup, for those of you in Denmark). I brought along the old heater blower and housing. We managed to find one from a Nissan Primera 1995+. It had exactly the same diameter on the blower wheel. It is a one speed, normally using external resistors. However I have bought the electronic motor controller that Oetker pointed me to, so I won't be using the switch, but mount the knob on a 22Kohm potentimeter..

I bought the blower, realizing that it would be a tight fit, as the motor protrudes a couple of centimeters further than the original.

After removing the blower wheel from the new motor (it was oriented to spin the wrong way) I gound a flat surface on the shaft so the original wheel could be mounted (don't push it all the way onto the shaft or it will drag on the motor mount). After testing the motor (4329 rpm at no load), cleaning and lubricating it, I inserted it in the housing and did a test fit in the blower compartment.

It did not fit. Angry

The corner of the inner fender was in the way, but after removing a bit it still would not go into the compartment. The motor was 1+ cm too tall. So, I cut an opening in the back of the motor case (plastic) and found that it did not support the motor in any way. Encouraged, I cut off about 1,5 cm of the housing and sealed the end with duct tape held in place by a strip. Since the shaft stuck out a little bit I placed a plastic cap over it before applying the duct tape. The cap was not tall enough, so I ground off 2 mm of the shaft that stuck out. Success. The fan now slid into the compartment without problem.

One thing to realize is that the new motor assembly does not have holes to allow the air into the Murena housing. I had to cut them with a hole saw, but that was easy.

After mounting the fan and connecting it using the original connector (just two wires, but remember to swap +/- because the motor needs to spin the opposite direction) I jumpered it to the battery. It draws 10,7 amps and creates half a hurricane in the car. Grin Grin Grin

Tomorrow, if I get a potentiometer that fits the dash, I will mount the motor controller and wire it up to the fan.

Pictures below.

« Last Edit: September 01, 2010, 10:15:26 am by Jon Weywadt » Logged

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Jon Weywadt
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« Reply #8 on: August 31, 2010, 10:45:14 pm »

I meant to include these photos too, and mention that duct tape is excellent to prevent dust and shavings from entering the motor/bearings while ginding the shaft.

I also forgot to mention that you can screw the new blower onto the housing, using the original holes, (though with screws that are appx. 8mm longer). You can see it on the photo also showing the electronic motor controller. I later decided to add extra screws, making new holes in the blower frame.
« Last Edit: September 01, 2010, 09:00:35 am by Jon Weywadt » Logged

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Oetker
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« Reply #9 on: September 01, 2010, 09:22:11 am »

It takes some effort to accomplish but the result is there.
You measured 11.7 Amp current, so it is possible to go for a smaller module to adjust speed.
The same seller has also 15 Amp modules for half the price, and they are smaller, but I think the 30 Amp module is more robust.
Better ventilation in the Murena is a must, because the original ventilator is in my opinion much to weak.
Good job Cool
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I feel like Jonah, only my fish looks different.
Murena 2.2 Red 1982. Murena 1.6 black on places.
JV
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« Reply #10 on: September 01, 2010, 09:27:48 am »

Very interesting!
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Jan Verdam
richard
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« Reply #11 on: October 06, 2010, 07:45:45 pm »

Hi,

why did you grind the axle ? couldn't you use the blower wheel that came with the new blower ?

Richard
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Jon Weywadt
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« Reply #12 on: October 07, 2010, 08:59:59 am »

Hi,

why did you grind the axle ? couldn't you use the blower wheel that came with the new blower ?

Richard
Hi Richard.

Unfortunately not. The wheel that came with the blower was meant to turn in the opposite direction. A centrifugal blower wheel must have the cup-side of the squirrel-cage in the direction of the rotation. Otherwise it does not move much air. The original wheel required the flat surface on  the shaft and it was no problem grinding and filing the new shaft to fit.

/Jon.
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richard
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« Reply #13 on: October 08, 2010, 10:52:09 pm »

Okay, i did not think of it that way, in that case i have to change the blower wheels also because i am changing motors also.

Quote
Tomorrow, if I get a potentiometer that fits the dash....
what kind did you use for this ? It's not very clear what type pot meter is on the device, is it 22k ?

thanks

Richard
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Jon Weywadt
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« Reply #14 on: October 09, 2010, 11:41:43 am »

Okay, i did not think of it that way, in that case i have to change the blower wheels also because i am changing motors also.

Quote
Tomorrow, if I get a potentiometer that fits the dash....
what kind did you use for this ? It's not very clear what type pot meter is on the device, is it 22k ?

thanks

Richard
The potentiometer that comes with the devise is too small to be used with the original knob. I replaced it with a larger one (physical size) that has a 6 mm shaft. It also needs to be filed flat to be used with the original knob. Which I chose, to keep the original look. The value for the one I got was 25Kohm, but that is close enough to the 22Kohm that came with the controller.

Regards.
Jon.
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