Heater switch not working

Brian_warner@btinternet.c · November 12th, 2005, 4:28 am

Hi, now the winter is coming I have just tried my heater and it doesnt switch on. I have checked all the fuses and they are fine? Coolent level is fine. It must be electrical becase the blower doesnt run. Any idea's?

Thanks

Grants · Post by **Grants** » November 12th, 2005, 5:12 am

Hi Brian - any of the lights work on the HVAC unit? - Just so we have an idea if theres any power getting to the unit. I'd also suggest trying all fan speeds as its pretty common just some of the speeds stop working and let us know.

Cheers and hope we can help sort this out!

Brian_warner@btinternet.c · November 12th, 2005, 6:34 am

Hi, no HVAC lights come on, have tried all speeds, it would definatly seem like a power problem. This issue occurred once before and the garage sorted this out followin an offside wing and fron bumper replacement? I dont have a wiring diag so cannot follow through the loom and there seems so many relays.

Brian_warner@btinternet.c · November 12th, 2005, 6:56 am

Sorry, Yes the AC light does come on? I thought it was dead but checked this again and the light does come on.

Regards,

Grants · Post by **Grants** » November 12th, 2005, 8:43 am

Theres some diagrams here:
http://www.mx3er.com/info.html

If you look at this one:
http://www.mx3er.com/info/1993%20Wiring%20Diagrams.pdf Figure 8 grid position B28.

First thing I'd be replacing the 30A fuse number 16 (heater) to make sure its not that, even if it doesn't look blown. And test the fuse recepticle for power (ignition on). That then powers the blower motor constantly (and the ground is switched).

Looking at the diagram above, HIGH speed bypasses the resistor assembly so thats a good start. If the fuse is ok, pull out the switch mechanism and try shorting the BLACK wire to the BLUE / WHITE wire - the fan should run full speed (ignition on).

The outcome of this will determine what to do next.

It looks like the resistor assembly is ok (or else it would run in some speeds), it seems unlikely to be the switch (surely one speed would work), that leaves the blower motor itself or the power supply to it. Seems unlikely that the previous work done would have something to do with it but who knows.

Good luck with it - let us know if we can be of more help.

Mazda_Power · Post by **Mazda_Power** » November 21st, 2005, 12:20 am

OK, I have a '94 RS and it's having similar problems. The blower only works on setting 4. The AC light will come on on settings 1-3, but will turn off on setting 4. Also it won't switch to vent... any ideas?

Brian_warner@btinternet.c · November 21st, 2005, 6:28 am

Sounds like your switch resistor is faulty, I'm not getting any fan activity at all although I do have power to the switch. I havent had the time to explore further with a multimeter yet and most likely will have my son put it in the garage for repair as he is miles from my location. Good luck.

Grants · Post by **Grants** » November 21st, 2005, 6:38 am

Brian_warner@btinternet.c wrote:Sounds like your switch resistor is faulty, I'm not getting any fan activity at all although I do have power to the switch. I havent had the time to explore further with a multimeter yet and most likely will have my son put it in the garage for repair as he is miles from my location. Good luck.

I'd agree with that Brian. Pity you can't get convenient access to sort out your own problem. Good auto elec shouldn't charge too much anyway hopefully as your fault might be fairly easy to isolate. Main thing is to get it working

Brian_warner@btinternet.c · December 5th, 2005, 5:13 am

O.K, Didnt need to get auto electrician, borrowed a multimeter and traced through the circuit. No body mentioned a circuit breaker installed just above the fusebox which had tripped? Therefore if problem with heater, check the fuse and the circuit breaker above the fuse panel, this breaker is marked Heater!

Grants · Post by **Grants** » December 5th, 2005, 7:42 am

I'd rather hope you didn't get an auto electrician to turn on a switch. Of course we didn't mention to check the circuit breaker marked "heater". Its not on the diagram for the mx3 and my car certainly hasn't got one.

What car and model have you got anyway? Where are you anyway so we could make an educated guess?

Woulda thought you'd turn a switch labelled "heater" on before asking people to research a problem that was so damn obvious.

Why did you say

I'm not getting any fan activity at all although I do have power to the switch.

when that now proves to be obviously not the case at all?

"No body mentioned a circuit breaker installed just above the fusebox which had tripped?" just makes me wonder why I bother. All we have is the information supplied BY YOU.

Brian_warner@btinternet.c · July 11th, 2006, 2:58 pm

Just for the sake of clarity, the CB is hidden above the fuse panel and out of site, you can only find this if hanging upside down and inside out and dangling from the door????

If you put a multimeter across the terminals and it reads +12.8V, that's a good indication that power is present at the switch, however that doesnt mean the fan will run neccessarily as this could be a relay that gets switched on and the CB controls the high power side of the circuit?

I can only explain the symptons and the facts, however I'm greatful for the help and published this for the benefit of other's who may suffer a similar problem.