kdurg

I have heard of several 993 owners' advising to keep an extra DME Relay in the car in a case of original failure.

Just for kicks, I checked the fuse box and to my amazement the current DME has a 944.615.227.00 part number ??

The car runs fine and I am of the persuasion to "not fix it" unless it is broke.

So...what gives here ? Should I replace this Relay with the 993 part I have new....or am I fine with the 944 part already in the car ???

Did the 944 and the 993 use similiar DME specs ????

TIA BIGTIME !!!!!

Stevarino

keith:

There is an updated 993 replacement relay available. I replaced the existing relay with the updated part and keep the old relay in the car as a spare.

That part no. is 993.615.227.00

My understanding is that this is a must do. I got mine from the guys at Suncoast Porsche.

nile13

Keith, the 944 relay is the correct original relay for your 993. The later updated part that Steven noted came later and is available as a replacement.
You can buy updated part and keep it as a spare. You can swap them and keep 944 part as a spare. It doesn't matter, relays either function or they don't. And I would be amazed if the updated part is any better than the original one, afterall, this is German electronics (having said that I must say in all honesty that P-car seems to have fewer electrical problems than my Corrado and a pair of BMWs, both with fewer miles... knock on wood).

Greg Fishman

Get a spare. If it quits you will not be able to start the car. Murphy's law will have it that your wife will be driving the car the day the relay chooses to die.

STLPCA

Mike
1. This relay doesn't always drop dead. It can cause periodic problems.
2. Be amazed - in a side by side, the updated part is obviously more robust & seems to have cured the problem. My P dealer has a draw full of failed "944" relays, with but a couple of the "993" parts.

Common wisdom around here is replace the 944 relay w/the 993 part & keep the old one as an emergency spare.

nile13

Dan, I'm aware of intermittency of the problem. If I understand correctly, it's mostly due to temperature. My intuition as an electrical engineer tends to agree.
I have no doubt that 993 update is beefier and better made. I'm expressing a doubt that it will have fewer problems than the original part after a period of several years in the car.
I'm very jaded on this and I admit it upfront - I'm much more used to Japanese electrical reliability.

Having said all that, I will soon have a replacement 993 relay in the car just in case Although at 117K miles and exactly 10 years of use the original is still OK, knock on wood.

914und993

These relays supply current for the four O2 sensor heaters, in addition to the DME and fuel pump (I think). This is quite a bit of current, and some cars seem to draw more than others. The failure mode of the DME relay is one of overheating from high current draw, not a mechanical failure. A search of the archives should turn up threads with detailed illustration of what happens to these relays.

If the newer relay has a higher current handling capacity than the older one (and it appears it does), upgrading should be a no-brainer.

Chip

993,951,944

Yes, the DME relay powers the fuel pump and
the four heater coils to the O2 sensors.

The relay was intended to power just the fuel pump
of the 944 series. It was not designed to handle the
additional load of the O2 sensor heaters.
The O2 heater heaters actually use more power
than the fuel pump! ( An engineering oversight )

After experiencing a failed DME relay,
I measured the current draw and found it
to be greater than the relay contact rating during
the initial O2 heater warm up. After warm up,
this current would drop just below the relay
maximum rating. The upgrade relay is improved;
but it falls short of handling the the high current
load on a long term basis.

GMS

The 944 part number relay fails on 944s after about 8 years. We change them as part of preventive maintenance. Of course, on my 944 the old one was never changed and then failed..

Edward

Just an academic question, especially for you EEs out there:

If the overload is due to the extra current draw of the heater coils to the O2 sensors, then would it stand to reason that fewer failures would come from 95s since they have only one O2 sensor? Moreover, with the new part, could one can even expect greater service life/reliabilty since the draw will fall that much lower than the maximum rating?

Edward

graham_mitchell

Has anyone experienced a faulty NEW DME? (either old or revised versions)