I’m not sure if this is just par for the course but on recent long trips on the motorway my Mk1 1.8 is not warm at all - not only is there no detectable heat, it does not clear the windscreen (even on full blast on the correct settings) plus to make matters worse - when you turn on the fan it sends a really icy blast into the passenger footwell - do they all do this or is my heater knacker/disconnected - any suggestions?
This is certainly not normal.
Even in cold weather, if I have a reasonably warm fleece on and the windows up, even with the roof down I can get too hot, especially at motorway speeds.
Have you checked the coolant level, since this is what goes through the heater matrix?
I assume that the temperature gauge goes up to around the half way mark.
If there is coolant, then I would suspect that the heater control is not adjusting the source - I think it just moves a flap, but couldn’t say for sure.
I know the heater in a MK2/MK2.5 is different, but in my car (MK2.5), if you look through the glovebox area, you can see the able that adjusts the heat - not sure if you could in the MK1, but I’d think so - might be worth making sure it is connected (if even present) at both ends.
Does the engine get up to normal working temp within about 5 minutes? If no, then you probably have a stuck open thermostat----
As I remember, you used to be able to buy summer/winter thermostats. These were denoted by (believe it or not) an S or a W stamped on the main body of the unit. Although I agree with Geoff, whilst you have the unit in your hand, just have a quick look to see.
Gary
It could be a blocked and corroded heater matrix but, before going down that road do the following.
Empty the coolant and flush and back flush the system a few times until the water is completey clear.
Fit a new genuine Mazda thermostat. Fill the engine with a new water and antifreeze mixture and then run the engine to temperature. If this helps only slightly I think the Heater Matrix is probably clogged up.
Someone recently posted a thread on here about replacing his heater matrix but unfortunately he had no pictures but it may give you the confidence to DIY.
Ps Ask someone in your family to buy you a copy of Rod Grainger & Pete Shoemark Mx-5 Miata Enthusiasts Workshop Manual.
It is worth it’s weight in gold, as they say.
I would certainly go for the thermostat first, once replaced check for leaks in the cooling system, once the engine has reach running temp have a close look at the water header tank and see if you have any bubbles in the water, if so you have head gasket failure hope not. I had a ols vauxhall many years ago and some plon–r had changed the heater hoses over the hot feed into the return side of the heater matrix just incase check when you get the engine hot that usually the hot heater pipe is the pipe that goes to the top of the heater matrix.dont forget to adjust the strengh of anti freeze once repair is complete.
Alan
2003 1.8 splash green, sport, k&n typhoon air kit, style bars, front sus brace strut, ss grille, boot lifter
Thanks for all the help - i’m very glad that I won’t have to put up with a freezing cold MX5!
The temperature gauge goes up to around the half way mark fairly quickly and I did recently check all my levels and the car is running fine otherwise, so it sounds like it might be the thermostat/heater matrix - i’ll check it out.
Thanks again.
You know how to check the thermostat, in a pan of water brought to the boil on the gas or electric hob?
Turns out the previous owner had fitted a new stereo and after doing so hadn’t put it all back together properly - it wasn’t even connected up…
now works very well.
In fitting a stereo he had managed to disconnect the heater?
Not disconnected as in turned off but just not reconnected properly so none of the heat was actually flowing into the car…