ktonini

That was the first thing I tried - replaced both of them and double checked that the wiring was in good condition. A PO must have also had issues with the cooling fans because the wiring looked new and one of the old resisters was .9 ohm instead of .6. I put brand new .6 ohm resisters in and the problem persists unfortunately.

riouxc

Hello All,

Since I have issues with the reference sensor, even the ODB+ didn't make sense, I think I found the source...
First, My flywheel was not set properly... I readjust it once and for all (my flywheel is a 50% less weight than original and did not have markers... You need to remove the reference sensor set the pin in TDC mode and then set the timming belt accordingly.
Second, I did a major upgrade on the engine and since the engine was out, I just put the sensors BEFORE putting back the belll house. I had to cut the bellhouse a little bit to put it back with the sensors already there, HUGE MISTAKE!!!!.
Now, look at this Porsche tech note :


I just received the new parts, I have a 1986 944T, this notes is for a mistake they did in 1987...

Source of my issue (someone else picture)

Reference sensor with sleeve :

Don't need to buy new sensors.

jeyjey

It looks like if you replace your sensor bracket now you have to go with the shielding sleeves (the older bracket appears to be NLA).

Ftech9

The low and high speed fans run on parallel circuits. If the low speed fans where running, they can be overridden by activation of the high speed circuit. I would think if it is spontaneously switching between high and low speed fans that one of the "Temp Fast" activation sources is causing the issue. Most likely this is the temp switch in the radiator, but it could also be the AC refrigerant temperature switch (High Temperature Activation) switch for 944's up to 1988. This was changed to a high refrigerant pressure switch on newer 944's like the S2. It is also possible the fan relay is causing the issue, especially if it is one of the first revisions. There where several revisions which is a good indicator they where having issues with it.

To eliminate the AC refrigerant switches as causing the issue, you can simply disconnect them to see if the issue goes away. If it doesn't, you are left with the temp switch in the radiator or the fan relay,


- Joe

Tom Pultz

I did Joe's recommended troubleshooting on my S2 as I am having an issue with my fans... when they activate they immediately go to high speed. Using the diagnostic FT9 fan relay I can run the fans on low speed with the engine off, or on high speed with the ignition on, so those independent circuits are working properly. Disconnecting the AC pressure switch did not change anything [to disconnect, raise the headlights, pop the connector out of the plastic retainer (driver's side) and separate the two halves], so the culprit apparently is the radiator thermal switch, last changed in 2004. I have a new thermal switch coming from Delaware Porsche next week.

I also did testing with the release candidate 2 SS relay with my 951 and everything checked out great and both low and high speed fan circuits worked normally, which is another factor pointing to the radiator thermal switch in the S2. Will update when I get that resolved.

michael7810

On OBD+, is the water temp reading from the DME temp sensor (I assume it is) or the temp gauge sensor?? I have a suspected bad DME temp sensor which I can test via the Clark's Garage method but since I have OBD perhaps I can troubleshoot without removing the DME connector. Thanks

ktonini

Thank you guys so much for the pointers. I tested the AC pressure switch and it made no difference, so it seems like that's not the issue. I've ordered a new temp switch, but the washer is a special order item so it all should arrive next week. I wouldn't be surprised if the issue is just the temp switch since I can hear the relay clicking when the fans alternate, and there was a small coolant drip over the switch that I dealt with a few months ago.

riouxc

I think I busted my OBD... Now, I lost WBO2 and barometer....



I installed a MSD Digital 6AL and the engine started for a fraction on a second, second start the starter just froze and smoke was comming out from the negative battery... .
I removed the MSD module. The car started but no more WBO2 or barometer readings and the white LED on the board is flashing...

I still see a lot of RPM errors and counting the double of starter tooth.

Joe, can I send you this on a rush ?
Thanks,
Charles

Ftech9

Yes absolutely, I will get you fixed up!

riouxc

Thanks,

I still need to inspect a little bit before.. I have a constant double count(264) on the flywheel tooth. But the signal is OK , tested with my scope on the ECU.

In the tech docs, it is stated that the reference pin need's to be 5mm tall. Distance from the flywheel and the reference would be 5.8mm ... If shorter, the signal would be a bit corrupted.

Work to do to night.

riouxc

Why do I get double readings on the ring tooths ?

Ftech9

That is odd to have exactly double the expected tooth count. I will review the code for the firmware, could be a bug.

- Joe

riouxc

As I have a LR chip on board, I will check with Ostrich II with your bin for 28 pin 951. I don't know much about what's the extra code in that EEPROM... Maybe there is a miscalculation on that side... Would ignore the second pass... This is very odd.

riouxc

HA! Found some very interesting tech stuff.

LR chip doubles the tooth counts! No issues with Joe's code at all.

riouxc

Here goes info from LR web site: "This latest generation of the M-Tune has some software and hardware enhancements that make it even better then ever. With Open Maps and Tables for example, now anyone with a EEPROM burner, or Ostrich Emulator can tune the DME's maps & tables with this new generation chipboard. With 2 times as often ignition timing calculations, MAF and MAP sensor sampling 2-1/2 times as fast, logging rate increases by 27%, barometric reads on start up, expanded FQS range for fueling percentage changes, and over 56 available maps and fabricated satin black power coated aluminum plumbing... you can see this latest M-Tune offered by Lindsey Racing has set the bench mark very high."

This will make the odd data exposed by OBD+. Now, we don't want to begin a war on this... Will look deeper on my side. Will try to create a map from LR tables on a Ftech bin file... Thanks to Ostrich2 !