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Magneti Marelli


Maverik
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I've got what I think is a Heater matrix out of "I think" a peugeot 307... this is what it looks like.

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I've got it installed in the truck cabin heater box now I'm just figuring out the wireing for it.

Now I did a wee trial and not a lot happend, does anyone know anything about these matrix's? i.e. specifications for them? I've trawled the magneti marelli website for a tech spec but not come up with anything at all.

I have been told that they have an output of around 1400w? but I have nothing to support this.

Does anyone know what they are designed for? and what I can expect with regards to how quickly these things heat up?

Cheers

Mav

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Ok, just found another one thats advertised as a "air con heater resistor"... anyone know what one of those is and what its for?

Now I have a not so funny feeling its not what I wanted it to do...

Edited by Maverik
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I think it will do what you want it to.

Pop a multimeter on the big brown one (live) and each of the others in turn. You should get a reading of a few ohms.

Then use P=V^2R to calculate power - you'll probably find each of the little wires is one heating element. If you switch on each one you will get a progressive increase in power output.

You can also use I=V/R to calculate current pulled by each element to size wiring correctly too.

I'll also add that at 1400W you'll need one hell of an alternator! That's about 120A for this heater alone, without having any other electrical devices on.

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Is it not P=V^2/R

There does seem to be 3 elements which give a resistance of 0.03 ohms... now putting that into P=V^2/R you get P=4800W... which I don't belive...

I did do a little trial and put 12v supply (40amp - protected) on one element and not a lot happend, then put it on 2 elements, I heard the alternator change pitch but thats all, then plugged the 3rd element in and it popped the fuses...

Its already on the heater box, so I had the fan on slow, blowing through it, so can't tell if it was heating up at all really, there wasn't any noticable change in air temperature (it was about -5 last night here, so i figured I'd notice a slight increase, i was frozen!!!)

It could be that its slow to heat up....

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Is it not P=V^2/R

There does seem to be 3 elements which give a resistance of 0.03 ohms... now putting that into P=V^2/R you get P=4800W... which I don't belive...

I did do a little trial and put 12v supply (40amp - protected) on one element and not a lot happend, then put it on 2 elements, I heard the alternator change pitch but thats all, then plugged the 3rd element in and it popped the fuses...

Its already on the heater box, so I had the fan on slow, blowing through it, so can't tell if it was heating up at all really, there wasn't any noticable change in air temperature (it was about -5 last night here, so i figured I'd notice a slight increase, i was frozen!!!)

It could be that its slow to heat up....

The heaters are probably PTC devices - positive temperature coefficient. What that means is that the resistance rises rapidly with temperature, which is how the heating is controlled. They are manufactured to reach a stable temperature. If they get cooled below that, the resistance drops, current rises and they get hotter.

Becasue of the low resistance, you may have to switch one at a time, let it reach a low current value, before switching in the next one. Can you borrow a suitable current meter and see if the current is dropping off?

I've not ever played with vehicle ones, only small (50W) ones for electronics heating. Have you tried to find a WSM for a 307? ISTR the very late Freelanders used PTC heaters in the dashboard - try digging in the RAVE manual?

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The heaters are probably PTC devices - positive temperature coefficient. What that means is that the resistance rises rapidly with temperature, which is how the heating is controlled. They are manufactured to reach a stable temperature. If they get cooled below that, the resistance drops, current rises and they get hotter.

Becasue of the low resistance, you may have to switch one at a time, let it reach a low current value, before switching in the next one. Can you borrow a suitable current meter and see if the current is dropping off?

I've not ever played with vehicle ones, only small (50W) ones for electronics heating. Have you tried to find a WSM for a 307? ISTR the very late Freelanders used PTC heaters in the dashboard - try digging in the RAVE manual?

Thanks for the info, will look into it! I need to set up a test rig to test it properly me thinks.

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I've got what I think is a Heater matrix out of "I think" a peugeot 307... this is what it looks like.

post-20087-063293500 1294393947_thumb.jpg

That looks just like what I want for my electric vehicle heating.

It could well be similar to ceramic heaters where they self regulate their current flow and hence temperature. Safest way in a car as it stops it melting the dashboard if the fan fails to blow.

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