MX-5 Foliage shredding machine

[oakes333]

1. My model of MX-5 is: 2.0l Series 3
2. I’m based near: Bicester
3. I’m looking for technical help or recommendations on: Heater / fuse board plug

I was driving my new (to me) MX-5 happily the day after I bought it with the roof down and started to feel a bit chilly so thought I’d try the heater. ■■■ an entire forest of chopped up leaves ad twigs suddenly emerged from all the vents with the full force of the fan on full power and filled the cabin even with the roof open, foliage flying off in all directions and covering me and every surface in the car. As a consequence I tried to turn the fan off but it continued on full power even though the dial was turned to off. The only way I could finally turn it off was to pull out the heater replay from the fuse board. While doing this I discovered the sight in the two attachments.

I’m guessing they are shorting out but a quick perusal of the wiring diagram I found on-line doesn’t seem to correspond to the wiring colours. Please could someone identify what component this is and the best way to resolve the issue?

Many thanks

David.

[RichardFX]

Fear not!

That brown stuff on the plug is a waxy waterproofing applied by Mazda to seal the leads into the plug and thus help prevent the contacts corroding.

It’s not the only place they use it.

[Dean_S550]

The leaves and twigs probably came from behind the scuttle where the heater draws it’s air from. Definitely worth cleaning it out and sealing the grommets while you’re there.

Dean S550 Build Thread

Prevention being better than cure, I’ve removed and replaced the scuttle grommets and cleansed everything out. Clearly the scuttle had never been off but no evidence of any leakage. [IMG_20231112_155642] [IMG_20231112_155904] [IMG_20231112_162810] [IMG_20231112_173507] [IMG_20231112_173516]

[oakes333]

Thanks Dean. I had only bought the car the day before. God only knows where it had been parked before I took ownership. I think it’s a little too late to clear out that area since it has already been sucked in and through the fan. My primary concern now is I can’t turn off the blower on maximum without removing the relay. I suspect the plug in the photo is shorting out and needs replacing. What is this plug and how best to go about replacing it?

[RichardFX]

@oakes333

I suspect the plug in the photo is shorting out and needs replacing.

That is most unlikely.

Much more likely is the MOS fet that controls the fan speed has gone short circuit (maybe over-heated because all the leaves stopped it being cooled, or cooked by a shorted turn in the motor).
Snag: this is hidden on the blower assembly under the dash and a pig to get at. Several threads on the forum have discussed this and shown how to fix the problem.
This is one of the better threads

NC Blower MOSFET replacement

My model of MX-5 is: NC I’m based near: Daventry, Northants I’m looking for technical help or recommendations on: Replacing the blower “resistor” MOSFET Has anyone replaced the blower MOSFET (which Mazda call a “resistor”) in a RHD NC without dismantling the dash and removing heater etc? I’ve seen a couple of references to doing this on a LHD car, which indicate that it is possible but extremely awkward. There’s a back story here, but currently I have a working blower with the MOSFET hangin…

[oakes333]

Well, I got the fan out. Is there a hedgehog in there?

[oakes333]

I’m guessing the MOSFET has a short. Even with the fan cleaned and everything I can reach behind it cleared out and vacummed the air intake the fan runs at full irrespective of what the blower speed dial is set it…including off.
I’m not even contemplating removing the dash to get at it. I will have to get used to no heater.