Hi, after much interweb browsing over the last few days I have discovered the dreaded “leak behind the fuse box” has been affecting my 58 plate mk3. I have cured the leak and most of the secondary electrical issues have stopped (think headlights turning on). Unfortunately it now keeps blowing the starter motor fuse does anybody have a good idea?
Thanks in advance
Hi
Welcome to the forum.
Are you able so start the engine at all or does the fuse blow every attempt?
Richard.
Hi Richard,
It’s blowing every time without the engine starting, it bumps ok though
Jim
Hi jimlad,
Usual source of info is Mellens, but this link doesn’t give much help - http://www.mellens.net/mazda/Mazda-Miata-2008-2009/index.html
No overall wiring diagram, except for DSC, which doesn’t cover your problem. Only thing shown in detail is the main fuse box, while it says there’s another on passenger side, but not shown. I can’t see a ‘Starter Fuse’ as such, but on previous models (NA & NB) the main fuse covers the starter motor. On The NC, this appears to be the top single fuse in the main fuse box, shown as 125 amp. If that keeps blowing then the car will be dead as a dodo. (I imagine it’s also expensive, compared to lower rated fuse cost.)
There is some detail re the starter components, but mainly mechanical, rather than electrical, not much help there either. Only point I noticed is detail about an insulator on the starter motor itself, which shows ‘peeling’ and how to rectify it. Unsure if that causes a problem, as in your case, but other details in that section are beyond a normal DIY project IMHO.
So - while I’m not helping you much (for which I apologise) it looks like the starter motor, or the solenoid has a short circuit, but without actually looking at the car it’s difficult to describe where and how to look for the problem. Obvious solution is the get the car to either a good auto-electrician or to a dealer, but if you can’t start - and run it, then you are stuck with it I’m afraid.
Hi Gerryn,
according to mellens that is definitely not a diy project! For the avoidance of doubt the fuse that I’m having trouble with is number 27 ST 20amp (page 7 in electrical component locations) not the 125amp main fuse.
Thanks
Jim
Jim
I’ve just sent you a lengthy PM.
I tend to agree with what you have read in Mellens.
Richard.
Thanks Richard,
Although I didn’t smell anything this time I did have trouble about a year ago with the starter burning out (3 new starters thank heavens for warranty replacements!) I shall be taking it to the auto electrician in the morning.
Strange, but true - I did wonder what ST stood for, but without a wiring diagram who knows? Maybe Robbie can help? From what you say it does appear to be in the starter circuit, but where, and what it protects remains a mystery.
The Starting Circuit is shown on page 80 of the Mellens Wiring.pdf for the 2007 Mk3s.
The ST fuse only carries the current for the Pull-In and Hold windings of the starter solenoid, nothing else. This current is switched by the contacts in the Starter Relay which lives on that same fuse block inside the engine compartment. Obviously the relay is switching because that then allows the fuse to blow. So then the question then is, where is the switched current going?
Is there a problem inside the relay? Unlikely, but easily checked, unplug it and replace it with a known good spare.
If the Blu/Red wire from this relay to the solenoid is damaged and shorting to ground then that will blow the fuse. Easily checked if you can reach the solenoid, just unplug the wire from the contact on the solenoid, if the fuse still blows there is a problem with the wire. (There might also still be a problem with the solenoid, it might even have cooked the wire.)
If the solenoid windings are shorting then they will also blow the fuse. This is where it gets expensive.
Be careful.
Good luck.