Root cause of DME relay failure
 

There is a theory out there that most DME relay failures are caused by insufficient solder on the elecrical traces and that adding solder to the traces reduces the resistance and heating which makes the traces fail. Has anyone ever tried to do this? My 86 has the original relay, so one side of me says to not mess with it.

For $30, or whatever a new relay costs, is it worth the hassle of trying to modify the original one?

Buy two new ones, and don't look back.

My theory for electrical components is;

If it works, don't fix it (edited by moderator).

Maybe the compromise is:
- buy a new one and check by installing it.
- take the (good) old one apart and add solder...reassemble.
- check old one for function
- put one of these away as a spare...as we should anyway.

Some also say the horizontal and unsupported position of the relay places stresses on the soldered joints. Support from below with a soft rubber block.

---Wil Ferch

Are we talking about the DME relay or the DME itself? If it's the relay, stash a couple of spares and be done with it.

I have heard of the DME board coming apart, but that's a different animal.

My theory for electrical components is;

If it works, don't fix it (edited by moderator).

The DME relay fails because of two reasons;

1. the internal relays are not heated properly when soldered to the circuit
board
2. the DME relay is mounted in unsupported cantilever method by the end tab
which results in vibrations to the circuit board stressing the solder connections

I suspect quite a few DME failures are attributable to vibration also. The unit is not shock mounted/ruggedized, nor does it employ SMT components. Mine would function if the plug connector was tugged upwards, indicating a bad connection somewhere.

What are the signs of DME Relay failure?
Where is relay located? Is it outside the metal DME box, visible under the drivers seat?

thanks
mike
'86 coupe

Its between the Motronic box and the altitude sensor.