What's an ECM Relay?
 

The dilly is thus...

1996 Passat. Runs like a dream, except...it (seemingly randomly) won't start. Turn the key, you get a clicky/grindy noise that sounds like it's coming from the driver's side of the engine. Almost sounds like a solenoid problem. That's it. Doesn't try to crank, nothing. I was thinking starter/alternator, but IT EVENTUALLY TURNS OVER. Alternators don't un-die.

The circulation pump was on and making some noise when it happened yesterday. As soon as it stopped making noise, it turned right over like nothing happened.

The guy at the VW place was nice enough to look at it and tell me that for an intermittant problem, I'd be throwing money away, and he gave me some things to look for the next time it happens, to help narrow things down. His feeling was that the circulation pump was unrelated to the problem at hand, and that I possibly have a faulty ECM Relay.

So, what's an ECM Relay? What's it do? And what would it do if it was in the process of crapping out?

Thanks
MPEDrummer

Oh, almost forgot, it's not entirely random...both times it has done this, it was parked in direct sunlight on a hot day.

You said you were also thinking it could be a starter problem...did you rule that out? From the problem you described a starter would be my guess. That would produce a clicking noise if it was hitting the flywheel and not engaging, it most likely would work after a few attempts (or maybe moving the flywheel somehow) and until it did work the engine would not turn over.

Not sure what ECM stands for but my guess is that is along the lines off the engine management system.

That's probably a starter, or a starter relay. I don't think the ECM has a relay...just a fuse. Yes, the ECM is the engine computer...Engine Control Module. I would highly suspect the starter relay.

Thanks.

No, I haven't ruled out much of anything...I know enough about cars to know that I don't know enough about cars. I'm learning, though.

My guess, it's the starter. Mine just died recently, in a different fashion. Like badflsh said, if it clicks and does not turn over, but eventually does it's usually the starter...the ECM really has nothing to do with it.

i've had that happen to me recently!

If the VW tech suspects the ECM relay it's for a reason. People in cold climes frequently run into a situation where a relay will contract in cold temps, completing a circuit. This is seen as a "stuck" horn, for instance. The reverse must also be true-- a relay exposed to heat would have its contacts expand to the point where it couldn't work until it cooled. Also, you may have more than one identical relay controlling different functions, if so a defective one can easily be found by swapping . I don't know jack about VW's but this may help.

MPED- A relay is basically a switch that is operated by another switch.

Say you have a circuit wih a lot of power running through it, like say your starter. It would be very unsafe to have that power running through wires directly into the ignition. Tha chance for shock and otehr malfunction would be too great.

So a relay is used, the ignition switch has a wire that is connected to a relay that completes the circuit to engage the starter.

Get me, or did I just confuse you?

I have no advice for your situation besides agreeing with a starter wiring culprit.

circulation pump? as in water pump? or ac?

Beats the hell out of me...it's got a line going into the blower, and it's right behind the engine block.

bet you a lot of money its your relay. When some relays start to die, their symptoms first become apparant when they're hot. This is a very common problem on Hondas as well. Hope your relay is easier to get to than mine!

Bam.

It was the ignition switch. As the problem progressed, I discovered that smacking the steering wheel would usually cause it to fire right up on the next try.

And yes, this was discovered by taking frustrations out on the steering wheel the first time :)

MPEDrummer

ha ha, I'm glad you figured it out...even if you did have to resort to violence ;)