Hi all, I am having some problems with my electrics, on my mazda mx5 mk1 1990 model it started a week ago. I opened my electric windows then closed it so i know everything was working ok. When i turned car back on again after work, the drivers panel was dim, I turned the heater on to demist windscreen all that happen was my hazard lights lit up and all gauges stopped working, when i switch it off again gauges work, the gauges stopped working when i tried to use electric windows, they didn’t work either. I have checked all fuses and taken panels apart to check wiring is not worn and shorting across, all seem ok. I have checked that nothing wet all seem dry. Anyone else ever had this problem Steve
Sounds like there is a common earth point lose or bad connection.Take a look behind the dash frame and any metal structures and possible door A post footwell wiring.
I had a fault on my mark 2 which was like yours but intermittent, I checked all the wiring without success an auto sparks found it to be a frayed wire in the main fuse box in the engine bay. It was where the wires entered the fuse box from the bottom a couple of wires had somehow rubbed and frayed.
Might not be your problem but worth a look.
Does the engine start? If yes, then let’s assume the battery is O/K; If No then the battery is either shot, low and needs charging, or the alternator isn’t charging. If you have a multi-meter, then the battery voltage (with nothing switched on) should be slightly above 12v.d.c. - Measure across the battery terminals. - Are the connections tight by the way?
If the alternator drive belt is loose - it needs tightening. If it’s broken, it needs replacing. If that doesn’t work then the alternator is kaput. If the engine starts, then measure the voltage (again at the battery terminals) with the engine running the charge voltage should be between 13.5 - 14.5 Volts D.C. If it still reads 12V, then the alternator is the problem.
Sort out the basics, then let us know what’s still not working. If you’ve already done this then let us know, it’s a process of elimination, and these are the first steps.
Multi- meter - Halfords sell at a reasonable price. You need one that will check D.C voltage, A/C voltage,
Resistance and current, preferably up to 10A - more if you can afford it! Always handy to keep in the garage, or the house - if there’s an electric problem that’s why you need a meter that reads a minimum of 250V.a.c. However, if you aren’t happy working on house electrics (better safe than sorry) then ignore the A/C working voltage altogether!
Hi thanks for reply, it a new battery and the alternator new belt last year, everything else works switches on the lights work etc, I will check wiring as I big feet and often touch under the dash etc, I checked under the fuse box under the bonnet as well, and they look ok as well. I will check the earth, as when I have just engine running all dash ok, as soon as I switch windows on or heater all lights glow and all gauges just drop to zero, so earth could be the answer. I try it tomorrow thanks for info.
Steve
Possibility there’s a semi-short to earth, via a resistance - or a fuse would blow. Granted it could be a poor earth on the dash circuits, but then they’d act up when the car’s moving. - Does (or did) this happen?
I’ll give it more thought later - about to eat!
could be a short on the ignition key switch? windows & heater fan (also wipers) go through there…
A short circuit would cause a fuse to blow ,or wires to smoke.So I don’t think that will be the problem.The fact that the fault occurs when the fan blower is switched on,tends to indicate that the earth path for the blower circuit is trying to find an alternative path to ground.Perhaps take a look up behind the glove box at the fan wiring.
Steve -
I have to access my Mk 1 files via adobe reader - which is painful. Circuits are individually placed independently on different pages, so it’s difficult to see cross relationships between each circuit.
Initially my queries would be - 1) Does the engine still start O/K? 2) does the heater blower motor work?
3) do the windows work? Try 2 and 3 separately, with the engine running.
Can’t fathom why the hazards come on, that’s weird! What happens if you switch the hazards on separately?
Yes - except I said it could be a semi-short circuit - or the fuse will blow The heater control switch has a number of resistors on the earth side of the blower motor - if the motor is jammed, or has a partial short in the windings, then it will draw current through that resistance and the resistors on all but the ‘Full’ position, which is a direct path to earth. That might cause the fuse to blow.
There’s two possible causes here - 1 is a poor earth on the instrument panel circuits - actually two earths - and 2 a high current drain which causes instruments to dim. This would also affect the headlights, so we haven’t gone into that yet.
And then there’s 3 - low battery voltage and poor charging circuit, yes, new battery and alternator belt fitted apparently twelve months ago, but do we know if the belt is still tight - or the alternator works O/K - the belt may just need tightening, or the belt replacement and new battery may indicate previous charging problems?
Circuits with poor earths don’t “try to find an alternative path” - there’s either one available or there isn’t, “trying” brings in thoughts of AI - and we haven’t got that far yet! (TG)
My intiial thought was ignition switch, as someone else has suggested. The contacts burn inside and can give strange symptoms.
Hi this has made me think about three years ago when I wad driving things like windows and thinking about it the heater also used to go off when I hit a bumb. I used to wriggle the keys in the ignition and they were ok again. Do you think I need new ignition switch when it was ok I just left it alone
Steve
Those symptoms certainly sound like ignition switch problems. I’ve stripped them and cleaned up the contacts before now, but ultimately the best repair is to replace it. You can just change the electrical part on the end of the barrel.
Thanks I try that tomorrow try cleaning and then get new one.
Steve
Thanks Robbie - Experience over conjecture works everytime!
Hi thanks for advise. I took off ignition switch and it looked good. cleaned it fingers crossed but it wasn’t that. I then looked at the earth behind the centre column. I remembered years ago put new radio in and went straight to it and cleaned contacts up and recut end puy it back on and I had heater and windows back. Put everything back together snd well pleased.
Got up next morning and it stopped working again so did it all again and nothing. I then moved another wire and it started again. So I know where problem is I just hope it stays ok now and it wasn’t just luck I moved a wire and where it had split apart I just moved wire back together by chance I soon find out.
One drew back I touched the earth radio wire with earth wire and blow the radio dont understand why as it was earth to earth.
Im writing this on smart ohone it hard to read the screen so excuse spelling mistakes.
Steve
There is current in there somewhere - sounds like a power short to the radio earth - check the wires with a multimetre to locate the live feed.
Hopefully just a fuse blown on the radio.
Check the wiring near the radio Steve - there is often an inline fuse.
Failing that take the radio apart - there may be a replaceable fuse inside.
Good luck!