DME Relay - Failure and Repair
11-06-2011, 07:02 PM
#31
Rennlist Member
Thread Starter
The best part is this DIY may get someone that is stuck on the road rolling again, if they can get access to a soldering at a nearby home.
Keeping a spare DME relay is the best solution, or at least pop the cover on the on-board relay every year and inspect it.
11-06-2011, 07:05 PM
#32
Rennlist Member
Thread Starter
Simply heating up old solder joints that weren't good in the first place or just adding fresh solder on top of old, is asking for trouble again.
11-08-2011, 10:12 AM
#34
Rennlist Member
Thread Starter
A RL member PMed me with the following...
Everything will fail in time; we can only make it as reliable as possible and certainly fix quality control issues which is why these relays fail. The contacts themselves on my relay looked like new, so if that is the case with all relays, that is one area that isn't of concern.
To achieve what the member asked, I would resolder all joints.
To do so, I would desolder all joints first using desoldering braid and flux, and then make sure all PC board pads and pins protruding through the board, are clean. I used Q-Tips with lacquer thinner or acetone to prepare the board for soldering. Solder joints need to be clean to get a good reliable joint.
You will need:
After soldering all joints, clean each joint with Q-Tips dipped in lacquer thinner or acetone. The solder joints should be smooth and flow nicely into a volcano-like shape; they should also be shiny.
Thanks for the great post on this.
Was wondering - given the fix you discovered, is there a way to do a preventive permanent fix on the DME so that it cannot fail.
I carry a spare, but it would be great to just eliminate the issue completely.
Was wondering - given the fix you discovered, is there a way to do a preventive permanent fix on the DME so that it cannot fail.
I carry a spare, but it would be great to just eliminate the issue completely.
To achieve what the member asked, I would resolder all joints.
To do so, I would desolder all joints first using desoldering braid and flux, and then make sure all PC board pads and pins protruding through the board, are clean. I used Q-Tips with lacquer thinner or acetone to prepare the board for soldering. Solder joints need to be clean to get a good reliable joint.
You will need:
- desoldering braid (some are impregnated with flux)
- flux for electronics
- solder for electronics
- a soldering iron with a small tip
- proper soldering technique
After soldering all joints, clean each joint with Q-Tips dipped in lacquer thinner or acetone. The solder joints should be smooth and flow nicely into a volcano-like shape; they should also be shiny.
11-01-2012, 10:28 AM
#36
Rennlist Member
Thread Starter
This is the newer "993" relay now supplied by Porsche and the one that I carry as a spare.
I can't comment on its reliability, but looking closely at some of the solder joints, they do not look any better than those on the older and originally supplied "944" relay. Make a change, but miss the boat!
I can't comment on its reliability, but looking closely at some of the solder joints, they do not look any better than those on the older and originally supplied "944" relay. Make a change, but miss the boat!
Last edited by IXLR8; 11-01-2012 at 11:19 PM. Reason: Cleaned up this post.
11-01-2012, 01:32 PM
#37
"Everything will fail in time; we can only make it as reliable as possible and certainly fix quality control issues which is why these relays fail."
Read here for more info under 'Vibration'; http://www.systemsc.com/problems.htm
Read here for more info under 'Vibration'; http://www.systemsc.com/problems.htm
01-11-2013, 12:14 PM
#39
Instructor
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.
Thanks!
08-26-2013, 06:18 PM
#43
Rennlist Member
Join Date: Sep 2008
Location: Flyoverland - Central, Ohio
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the story continues . . .
Hand mine start to fail (intermittent start) on the '97.
944 part number (assume original, 90K miles).
Replaced with 993 spare per Rennlist advice. Worked great!
Hand mine start to fail (intermittent start) on the '97.
944 part number (assume original, 90K miles).
Replaced with 993 spare per Rennlist advice. Worked great!
03-09-2014, 09:40 PM
#44
Instructor
Wow! A fix that REALLY works! Many Thanks!
My garage queen RS America with about 56K miles just up and decided she wasn't going to start yesterday after not being used for a couple of months. Had a couple of occasions several months back when she was difficult to restart but I had attributed that to perhaps a case of slight over flooding but didn't know what to otherwise make of it. With plenty of fuel, a strong battery and yet a car that refused to start up even though it was turning over, I thought I had a real problem on my hands. So out of desperation I turned to the internet to search for the history of hard starting 964s and their presumed cause. Found this thread yesterday morning and followed the storyline. Pulled the DME and opened it up by using an Exacto knife to remove just one of the two tiny plastic lips that locks/holds the case onto the motherboard and internal apparatus. Nothing appeared to be bad including the soldered joints. But I went ahead and got some solder braid and went after the two central joints. I de-soldered them to where they appeared to float free then went ahead with some rosin core solder and dabbed some new solder in place. One other joint looked a bit low on solder so it just dabbed some new solder on there too. And that's absolutely all I did. Put the DME back together, sprayed some WD-40 on the bottom spade contacts, wiped that off a bit, then plugged the DME relay back in. The car started immediately thereafter like she was brand new. Blows me away! And to think I was worried to hell and back that I had a fuel pump problem from all the lousy ethanol in gas. I simply can't thank the original poster for all the info and pics!
