7 replies to this topic

[Francis Hu]

I keep blowing the engine relay on my 1990 Miata.  This is the relay in the black box in the engine bay next to the right shock tower.  I would come off track and shut off the car, then it won't restart.  It would crank over but no spark and no fuel.  It took me a while to figure out it was the relay, and once I replace it, then everything is good.  However, the relay will go bad again after a few more sessions.  I keep a couple of spare relays around now, but it gets expensive at $49 a pop.  Any help on tracking down the cause will be appreciated.

 

Francis

[Tom Hampton]

Do you still have any of the failed relays?

[Francis Hu]

Yes I have a bad relay.  Should I open it up to see what happened?  What should I be looking for? 

 

Also I just got the wiring diagram and it shows 1 line going from the main relay to the cooling fan relay. Can a problem with the cooling fan realy or circuit cuase the main relay to blow?  I blow the main relay after the car is hot and turned off. 

[Ron Alan]

Also just saw this happen on track(actually off track in pit!)...curious to see a reason here....

[Bench Racer]

If you have a Mazda factory shop manual, it shows how to check the fan relay. Would also at the start, make sure the BLK ground wire is grounded, check before disconnect.

 

I have a wiring diagram off the net from Yorba Linda Miata. It shows 5 wires at the Main Relay. Injector fuse WHT-GRH, WHT-RED to ECU/fuel injectors/circuit opening relay/crank angle sensor, BLK to ground, BLK-WHT to engine fuse/cooling fan. 

 

Three things I hate in life, painting, pluming and sparks/electrical.

[Ron Alan]

pluming...making jam?

[RazerX]

Hi Francis,

 

I would check the fan wire for a short and the fan motor for a possible short.  You can check the by getting a 5amp fuse and "hot wiring" a direct feed to the fan with the fuse in line.  If it blows that fuse, it is your fan motor.

[Bench Racer]

pluming...making jam?

Yes, plumbing is much easier.