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As the heading suggests. I'm having problems with my other car stalling and not getting spark. Yesterday I stumbled upon a relay hidden away in the engine bay which when I pushed on it there was the sound of an electrical 'spark' and after that the car started again and got me home... It has died on me again today, and so I'm wondering if it could be a dodgy relay, or whether I need to investigate closer to check the quality of the wiring to it.

Thanks in advance

Yep, they can die - especially in the heat of the engine bay - or get carboned up contacts. If a replacement relay doesn't fix it, then it's probably a wiring issue.

Check with a multimeter- these are very cheap- not sure what to check? try yr library for auto elect fault diagnosis. Yr garage or auto elect may also do it for you- maybe they charge maybe not. Elect parts fail just the same as anything else.

The relay could be faulty or it could be the wiring or you may just need some contact cleaner.

If you want to narrow down the source of the electrical problem it’s best to use a test light not a multimeter. That’s what auto-electrician/mechanic use. You need a load (the light) to test the circuit on a car.

Thanks guys. I have a multimeter and test light so will have a play with them during the week.

Are relays all the same? Does the colour relate at all? i.e, green relays are all the same, black relays are different to green, but all black ones are the same as each other?

Don't know about colour but they will have different ratings depending on the current being switched.

The biggest problem with OEM relays is getting something to match the OEM wiring plug or cutting off the OEM plug and re-terminating the wires to connect to a non-OEM relay................if that makes any sense

All the testing in the world won't help if it's an intermittent fault.

Is it green? There is a relay in the electrical box near the brake booster that has tended to die on a few people. I think it's the fuel injection relay? Cafeine or Big Dog will know the specifics. Is a bitch to extract but after you do it's possible to remove it's casing and clean up the contacts. Though I dont think a replacement relay is all that expensive to buy from Mazda.

As for relays in general. I dont think the case colour is a guide to how the switching is arranged, it's more likely related to the type of circuit they are driving, ie green for fuel injection, yellow for airbags/safety devices etc. They are rated by how much current they can handle and how the switching works. They are a very simple device, just an electro-mechanical switch. Some are on until the coil is activated, and some are off until the coil is activated. Power is applied to a coil that becomes magnetic and attracts one of the switch contacts which then completes or opens another circuit depending on the configuration of the relay. They can only fail in 2 ways. By a break or failure in the insulation in the coil windings or if the switch contacts burn out and get carboned up and dirty. A pin guide is quite often incuded on the relay casing.

It's the \"other car\" that has the problem - non-Mazda.

oh, missed that bit JBT

Are there any specifications written on the relay? Jaycar stock a heap. If it's ignition, I assume it's going to be a reasonably beefy relay, maybe a 12v 30A or something like that.

If you yank it out and take it to basically any parts store they should be able to match it for you. I did the same thing for my ignition relay on my 5 and AutoOne came up with the goods. $11 - matching pin pattern and everything.

Is this the same issue which you want to Repco for that time?

Still having problems? Probably best just to replace it with a mazda

^^ Yep, same problem...

It is a green relay though Garry! Although in a Nissan.

I haven't had the chance to have a closer look yet, that's on tomorrow nights to-do list.

Yeah you're right JBT, I don't want to try testing for an intermittent fault, I'd rather just replace the two relays which are in this location, although pulling them apart for a look see could be interesting.

Thanks all, will update on progress when I know more.

Yep, looks like we've found the problem, you see the answer has been staring you in the face all along.

NMX516 wrote:^^ Yep, same problem...

It is a green relay though Garry! Although in a Nissan.

Anyways, if you can get the relay out and the top off it would be good do you can check for burnt contacts. If it is the relay you will probably find a trip to a wrecker to match it up to possibly another nissan one will be the go.

Well I seem to have traced the problem to a faulty fuel pump relay. The power to the ECU runs from there, so seems to then of course stop the ECU working.

Now I just have to find a suitable replacement relay. Jaycar don't have anything to suit. I guess I should check with a few auto electricians... I'm going to try for a new one though with the thought they might be more reliable than something second hand

Don't Nissan have them