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Author Topic: Murena 2.2 ignition doesn't work anymore  (Read 43553 times)
brinkie
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Previous owner of a Murena


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« Reply #45 on: September 09, 2007, 07:18:06 pm »

But beware. fusing things is no guarantee for safe electrical system. Example: The fan is now fused with 10 amps. So if the fan circuit takes more than 10 amps, fuse blow, everybody happy. But what happened to brinkie and krede is a bad connection on the switch. This is not a short or overload circuit! If this bad connection has a resistance of 0.1 ohm, and the fan takes 10 amp, than the power it generates in this bad connection is 10 watt!
10 watt doesn't sound as a lot but 10 watt can generate enough heat to melt things or worse.

(yes, electricity is my hobby and occupation) Wink
I usually follow a more theoretical approach Tongue

P = U * I, where U is the battery voltage of 13,8V and I the maximum current of 10A, which brings the theoretical maximum power dissipation to 138W.

So there can easily be 100W of heat being dissipated, which is well enough to burn a hole in the dashboard, or burn up most of the plastic isolation and generate nice smoke Smiley

Still, fusing of the heater fan circuit sounds like a good idea to me. While busy doing that, I could as well make new connections to the radio and the auxilary power connector (where the cigarette lighter used to be, but I'm a non-smoker)
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/Robert

Previous owner of a Matra Murena 2.2 (1981)
Bart_Maztra
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« Reply #46 on: September 09, 2007, 08:05:03 pm »

I usually follow a more theoretical approach Tongue

P = U * I, where U is the battery voltage of 13,8V and I the maximum current of 10A, which brings the theoretical maximum power dissipation to 138W.

This 138 watt is power used by the fan to spin around and move air. The 10 watt burning in the bad connection is calcutated as follow: U=I/R = 10amp/0,1ohm = 1volt. P=UxI = 1voltx10amp =10 watt.  (or P=Isquare/R) Tongue
Don't get me wrong. I don't say that extra fuse is a waste. Only it does not prevent burnt switches. But it does prevent worse if this excessive heat is melting other wires and cause short circuits.  Making extra fuses is on my "100 things to do" list too Wink
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roy4matra
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« Reply #47 on: September 09, 2007, 09:46:02 pm »

Lennart, how did you get the knobs off the heater control?


The 3 plastic heater slide knobs are held by a 'pin' on the metal arm locking into a hole in the plastic.  Actually it is not a very deep pin, but if the knobs are tight, as they should be, you need to open the knobs up slightly to pull them off.  Some will simply pull off as they are either loose, already spread open or damaged.  To open the back up is obviously difficult without the right tool, as you need to come back towards you with a fine tool poked through the heater slide holes.  We mechanics have what are called 'pick' sets.  These are small like a screwdriver, but the ends are pointed.  The ends are variously shaped, but they have straight, 90 degree, 135 degree, etc.  If you poke one with the point coming back at you into the back of the knob on the underside of the metal arm, and open it up slightly, it will pull off.  If you don't open up a tight fitting knob, something will usually break!

If you have a knob off and you look inside the rectangular fitting hole, you will see a ramp moulded in the plastic so that as you push it on, it automatically opens up and slides over the pin, and then springs back down and locks it on.

The fan knob just pulls off, being a tight push fit with a 'D' shape for correct location.

As for the topic of extra fuses, just bear in mind that for every fuse you add at least four extra connection points, and no connection is perfect so you actually increase the circuit resistance as well as giving it more potential trouble points.  You need to weigh the costs against the benefits in all respects.

Roy
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Bart_Maztra
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« Reply #48 on: September 09, 2007, 10:06:33 pm »

Lennart, how did you get the knobs off the heater control?


 ;)The best time to do this is 10 past 5 Wink
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Anders Dinsen
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« Reply #49 on: September 09, 2007, 10:42:55 pm »

The 3 plastic heater slide knobs are held by a 'pin' on the metal arm locking into a hole in the plastic.  Actually it is not a very deep pin, but if the knobs are tight, as they should be, you need to open the knobs up slightly to pull them off.  Some will simply pull off as they are either loose, already spread open or damaged.  To open the back up is obviously difficult without the right tool, as you need to come back towards you with a fine tool poked through the heater slide holes.

Thank you, Roy, that was just the information I needed Smiley

I did notice that it looked like there was some kind of lock from looking at the knobs from the underside, but I couldn't figure out how to disengage it. I will see if I can construct a suitable tool to extract the knobs without damaging them. I don't have any idea right now, but I'll probably be able to come up with something...

;)The best time to do this is 10 past 5 Wink

Absolutely, and stand on one leg and say "koochachoo"? Cheesy

- Anders
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
davidewanprice
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« Reply #50 on: September 09, 2007, 11:46:53 pm »

If you pull it will come off but i found you may damage the plastic, the plastic fits very tighly on to a metal shaft with a domed end, this ripped the plastic making it very easy to pull off in future but less than sturdy when re-fitted. Good luck coz they take some pulling. Are these switches still obtainable, and for that matter the black plastic sliding switches? looking at mine it will need doing sooner rather than later.
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Lennart Sorth
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« Reply #51 on: September 12, 2007, 12:42:56 pm »

If you pull it will come off but i found you may damage the plastic
I found mine were quite easy to pull off (with care), even when I got the car back in 1995 - they have probably been forced off by a previous  owner. The plastic isn't broken, but the hole may have been opened up a bit.

/Lennart
« Last Edit: October 05, 2007, 10:41:05 am by Lennart Sorth » Logged

Lennart.Sorth@matrasport.dk
Murena 1983 1.9i silver // Alfa Romeo Giulietta 2.0d 2012 white // Smart 4two cdi 2010 blue //
brinkie
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Previous owner of a Murena


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« Reply #52 on: September 25, 2007, 10:56:59 pm »

Well, finally, I've got my car back on the road! There are still a couple of things to fix, but at least she's running again and has been parked proudly in front of the house.

The issues I have to work on are:
  • Bad idling, especially when the headlights are up and the interior fan is at full speed
  • Interior heater gives warm air even when set to cold
  • The driver's seat fabric is getting loose

The first problem is either a vacuum leak or another electrical problem (both can be fixed with some searching I guess). The second one is described in Roy's FAQ so I have to unscrew the cover again and start working on that; the last problem will be fixed when I finally will decide to put leather seats in (which is constantly delayed as more urgent problems keep on popping up)

But in all those months I have been missing the car, I did almost forget what fun it is to drive a Murena. Especially when I got used to my girlfriend's shopping cart (a C3 with 68 bhp Diesel engine). She doesn't like the Murena but that's entirely her problem Wink
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/Robert

Previous owner of a Matra Murena 2.2 (1981)
Lennart Sorth
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« Reply #53 on: October 05, 2007, 10:47:10 am »

Excellent news!
so I have to unscrew the cover again and start working on that
If its only a small amount, you might get around it by adjusting the other end of the cable
(from the bonnet side of things)

Quote
will be fixed when I finally will decide to put leather seats in (which is constantly delayed as more urgent problems keep on popping up)
Same here, - when I bought my car in 1995, the drivers seat was torn as the previous owner was so short he had the seat far forward, so the seatbelt rubbed against the seat. Now, 12 years down the line, i STILL haven't got new seats,  BUT they are finally on order (!).


Quote
But in all those months I have been missing the car, I did almost forget what fun it is to drive a Murena.
Been there, done that. Several times during my 12 years of ownership actually - and had the same revelation when I finally got the car on the road again.

Happy driving !

/Lennart
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Lennart.Sorth@matrasport.dk
Murena 1983 1.9i silver // Alfa Romeo Giulietta 2.0d 2012 white // Smart 4two cdi 2010 blue //
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