DME Relay - Failure and Repair
07-20-2011, 10:05 AM
#1
Rennlist Member
Thread Starter
DME Relay - Failure and Repair
Background:
According to the date code on the relay casing, this is the original relay that came with the car when it was manufactured back in 1995.
The relay performed flawlessly in the time I've owned this 993 and failed shortly after removing the relay from the fuse & relay board. The relay was removed in order to pre-lube the engine after a long winter layaway. This enables the starter to crank the engine over thereby building up oil pressure while disabling the fuel injection circuit.
Removing the relay from its socket in the fuse & relay board was enough to cause a break in an existing faulty connection on the printed circuit board.
Having examined my sixteen year old relay (72,470 km - 45,040 mi), there really isn't any reason these should fail.
The two sets of contacts were in perfect condition as viewed under a microscope in my lab.
The single semiconductor, a rectifying diode on the board, is highly unlikely to fail. The same applies to the coils used as electro-magnets.
This leaves the solder joints; usually the cause of any electrical problems.
Solution:
The solder joints in the following photo were resoldered. The two solder joints within the yellow rectangle were the problem connections as the upper coil was intermittent when energized and only operated when pressing on the printed circuit board or side terminal (85b).
The following photos are for general information only...
The left side of the DME relay:
The front of the DME relay:
The right side of the DME relay:
The DME relay diagram on the case:
BTW, the Porsche part number on the top of the casing is 944.615.227.00. This relay is shorter in height than the spare DME relay (Porsche part number: 993.615.227.00) that I purchased back in Oct 2009 for $29.31.
According to the date code on the relay casing, this is the original relay that came with the car when it was manufactured back in 1995.
The relay performed flawlessly in the time I've owned this 993 and failed shortly after removing the relay from the fuse & relay board. The relay was removed in order to pre-lube the engine after a long winter layaway. This enables the starter to crank the engine over thereby building up oil pressure while disabling the fuel injection circuit.
Removing the relay from its socket in the fuse & relay board was enough to cause a break in an existing faulty connection on the printed circuit board.
Having examined my sixteen year old relay (72,470 km - 45,040 mi), there really isn't any reason these should fail.
The two sets of contacts were in perfect condition as viewed under a microscope in my lab.
The single semiconductor, a rectifying diode on the board, is highly unlikely to fail. The same applies to the coils used as electro-magnets.
This leaves the solder joints; usually the cause of any electrical problems.
Solution:
The solder joints in the following photo were resoldered. The two solder joints within the yellow rectangle were the problem connections as the upper coil was intermittent when energized and only operated when pressing on the printed circuit board or side terminal (85b).
The following photos are for general information only...
The left side of the DME relay:
The front of the DME relay:
The right side of the DME relay:
The DME relay diagram on the case:
BTW, the Porsche part number on the top of the casing is 944.615.227.00. This relay is shorter in height than the spare DME relay (Porsche part number: 993.615.227.00) that I purchased back in Oct 2009 for $29.31.
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Racer944 (09-12-2020)
07-20-2011, 02:26 PM
#5
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In a Porsche box.....yes at least $80 for my 993 Turbo (1997). I bought my first Rennlist Required DME relay for about $45. When the original one went bad, and I spent $250 for a flat bed tow to my indy shop, to be shown how & where the back-up relay goes (don't ask
) I ordered another one, just in case, less than 8 months later, for twice the price (Sunset).
Every 993 ower should replace their original DME relay. Or learn how to fix them like IXLR8. It's not a matter of "if" it will fail, just a matter or "when".
) I ordered another one, just in case, less than 8 months later, for twice the price (Sunset).Every 993 ower should replace their original DME relay. Or learn how to fix them like IXLR8. It's not a matter of "if" it will fail, just a matter or "when".
07-20-2011, 03:24 PM
#6
Rennlist Member
Good job. Thanks for the info Alex!
Cheers,
Tore
Cheers,
Tore
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07-20-2011, 04:42 PM
#9
Race Director
In a Porsche box.....yes at least $80 for my 993 Turbo (1997). I bought my first Rennlist Required DME relay for about $45. When the original one went bad, and I spent $250 for a flat bed tow to my indy shop, to be shown how & where the back-up relay goes (don't ask) I ordered another one, just in case, less than 8 months later, for twice the price (Sunset).
Every 993 ower should replace their original DME relay. Or learn how to fix them like IXLR8. It's not a matter of "if" it will fail, just a matter or "when".
) I ordered another one, just in case, less than 8 months later, for twice the price (Sunset).Every 993 ower should replace their original DME relay. Or learn how to fix them like IXLR8. It's not a matter of "if" it will fail, just a matter or "when".
07-20-2011, 10:49 PM
#11
Rennlist Member
yeah, that <$1 profit will bankrupt everyone
Are you familiar with the term "loss leader" ?
As I said on the other thread, good info and thanks for doing the work on this. It really could save someone on the road without a spare.
And they may get away without a soldering iron if they are lucky...
07-20-2011, 11:32 PM
#12
Race Car
Great writeup!
However, I would still recomend having a spare in your glovebox,. A few months ago, my original one failed 100 miles away from home. Thank God I had a spare. Once back home, I was able to repair my original that had 3 cold solder joints, similar to what yours had, and it has become my spare now.
However, I would still recomend having a spare in your glovebox,. A few months ago, my original one failed 100 miles away from home. Thank God I had a spare. Once back home, I was able to repair my original that had 3 cold solder joints, similar to what yours had, and it has become my spare now.
07-21-2011, 06:30 AM
#13
07-21-2011, 09:28 AM
#14
Rennlist Member
Thread Starter
But the purpose of the write-up isn't so that one can perform a roadside repair, but that the failed unit can be very easily repaired in minutes once your "spare" DME relay gets you home. Your "repaired spare" can then be reused...as a spare.
