Does anyone know of an issue (issues) that would cause our cars to ostensibly burn up DME relays?

About two weeks ago my car wouldn't start. I could hear the starter click once and then stop. For some reason it felt like the engine wasn't getting any fuel (I don't know why I thought that, but that's what occurred to me). I've never had a DME relay failure before, but I carry a spare in the glove box (this was a newer 993 part number, not the old 944 part like was in the car), so I swapped it for the one in the fuse panel and the car started right up. I thought this was strange but haven't thought about it since.

Today the same thing happened. I had another DME relay in the tool bag I used to keep in my 944, and upon replacing the one in the car with it the car started right up.

I'm now out of spare relays and starting to worry that there's something wrong with the car. Any ideas what might cause this?

Thanks,
James

 

To little current to close the contacts well ?
Intermittent current that does not keep the contacts closed , causing arcing /overheat etc of the contacts ?
To much amps running via the contacts causing them to overheat ?
Bad luck of the draw and getting a few bad dme relays ?
Bad contacts in the socket where the dme relay is installed ?

Have you pulled the old dme relays apart for a look see ?
Do we know for sure that the old relays are really bad ?
Have you put them in another car to test them ?

 

Indycam, thanks for the suggestions. I made my original post before I had a chance to check they relays. I've just made it over to my parents house and tried the `bad' realys in my dad's 993. It starts just fine with them in place. Dirty or corroded contacts in my fuse panel?

 

Well, this is going to be fun. I went back to the garage and put the old relays back into my car. It starts no problem with all three of them. I sprayed contact cleaner on the blades of the original relay, and plugged it back in. I wonder how long before it does this again...

 

Had a similar issue with my old 951. Turned out the relays were fine - the car kept frying DME's due to a bad ground in the bell housing.

 

Starter click once and then stop ?
Thats not a dme relay problem .
That could be a battery problem , a starter problem , a cable problem , etc etc etc .

 

James,
I had a similar problem - I now have three relays all in good order. I swapped them over and it started. Just kept swapping. When it started, I couldn't replicate the failure but found it often happened in the morning on colder days. I guess where the plug fell off but stick with me.

First I would suggest checking the battery connections and then clean up the connections on the DME unit under the front seat. Then clean all the easily accessible contacts to the top of the engine.

Then try turning on the ignition but not starting it. Rock the relay in its socket. See if you get clicks as it operates.

In the end I took the fuse and relay tray off and found a loose plug below with broken retaining nib. It is the one with the thicker wires about half way along. It looks a little scary under there particularly if the wiring is hard. Don't pull on the tray too hard incase you disturb anything else!!

Good luck.

 

Thanks for the suggestions guys. This week is pretty busy with work, but I'll poke around some more this weekend: check the fuse tray for anything obviously loose and clean the battery connections, DME and easy to get to engine compartment contacts.

I'll let you know what I find,
Thanks,
James