Rear Blower/ Footwell issues

[rekstein1]

1988 911 cab with Manuel heat lever controls.

things were working fine until they weren't. As with the approching cold weather I need my defroster working so I began to look into it. Read all the threads about blower issues the rear relay and testing procedures.
Checked the rear fuses all good.
Question hear is continuity of fuse is good but when checked for power on DC volts got nothing shouldn't one of those circuits be live since I think this feeds into pin 3 as indicated with my signal tracer. Just confused about this
CHeck the trunck fuses 1,2,7,8
Pulled the rear fan ran it with my 12v dedicated power source turns fine

began AJ88 cab and 86911 targa procedure and this is how far i got

testing at the connector for the relay in engine bay

Pin 2 to 7,8, 12v but to pin 3 started at 110 down to 4.4 so thats weird
JUst for the heck of it I continued
Pin 2 to 12 key on run instead of 12 vdc I got 5.2
pin 11 to 7 12 vdc
pin 9 to 7 12vdc levers up levers down .015
pin 7 to 5 with jumper rear blower comes on
pin 3 to 4 jumper nothing, footwell blowers did not come on as there is a problem with pin 3 power supply i Assume

Question what the deal with pin 3 and where do I check next?
Pin 12 and where do i check next?

For laughs I swaped out the red relay in the truck and there was no change in any reading"
Final question do the 88 have fuses on the foootwell blowers and where the hell are those things located

thanks for you help

[wazzz]

Here's is the internal schematic I made for the relay, at least part of it. As mentioned, pin 3 should be hot at all times, pin 12 should be hot with key on and start.
If not, check where power source is interrupted. Probably a fuse blown.

88 has fuses on footwell blowers. They were added directly inline to the blowers, so you'll find them there and nowhere else. But I guess they are ok and so is the relay. Find where power source is cut and once it is restored all should be fine.

[rekstein1]

where is the footwell blower relay you mention in your diagram located?.
Gonna recheck pin 12 with the car running and inline fuses on footwell blowers seems like a plan

[wazzz]

Both the footwell blower relay and the main blower relay that are shown on my diagram are actually two small PCB relays located inside the metal case relay in the engine compartment, i.e. the one you've been checking voltages on connector pins. The electronics driving these small relays is also built inside this case. We call it relay for short, but it is better called "heater blower control unit".

[wazzz]

Also don't forget to check fuses on the 3-fuse holder in the engine compartment. Fuse number 1 is a 16A fuse controlling power to pin 3. Check this fuse in particular.

As for pin 12, no clue. It is not fused and you should have power on this pin when ignition key is on.

[GH85Carrera]

Check this thread.

http://forums.pelicanparts.com/porsche-911-technical-forum/1161065-another-footwell-blower-help-request.html

It shows most of the problems and solutions.

[wazzz]

Glen, I wouldn't suggest to open the metal case relay until OP finds the reason why there is no power source to it on pins 3 and 12. These are external issues, best to check that first IMO.

[rekstein1]

went into the footwell blowers found frozen motor and blown fuse. lubricated motors and replaced fuses and reinstalled. each footwell blower tested with dedicated 12 v supply as well as rear blower all ran fine
Jump from front relay pin 30 to 87 footwell blowers ran





pin 2 to 7 and 8 12v still no joy on 3 with key off
pin 2 to 12 with key on no 12 vdc

confirming fuse 8 is as i have a 1988 Cabriolet is labeled rear window wiper, widescreen wiper, heat spray nozzle.

looked at engine compartment fuses only have 2 wired there is continuity but no power

Have opened up the one relay but agree that that is irrelevant till i get power to 3 and 12 pin working
Have a signal tracer where do I check next ?

does from fuse 8 in the trunk run straight straight to the rear fuses as #3 or does it stop somewhere.

The same question of number 12? where does it come from?

I do not have a wiring diagram a[appreciate everyone's help

will take a picture of the rear fuses tomorrow gonna take another stab at it.

My understanding for at least pin 3 is it runs in the rear fuse and then to pin 3 of the relay. I cannot get any power to the wire before the fuse? Whats up?

[rekstein1]

i been looking through the various online wiring diagrams am I correct in that power to the rear fuse box comes from the alternator?

[wazzz]

PM me an email address and I will send you an updated version of Carrera 88 diagrams that I am currently working on, putting all legends in English (they were in German) and correcting a few things. Not finished but pretty usable for what you are looking for.

Power source to the 3-fuse engine compartment fuse box seems indeed to come from alternator. Check the 14 pin engine connector, as power sources goes through this connector.

[aj88cab]

I believe Pin 12 comes from Panel 1, Fuse 8 on the trunk fuse panel. The manuals show the panel numbering in 3 sections (Panel 1,2, & 3). Panel 1 is the middle section of 10 fuses (why Porsche, why?), 8th fuse. So it would be 11th from the rear if counting all the fuses...not confusing at all, huh! Fuse 8 is shown on some of the diagrams floating around the internet for years, I think the Bentley Manual lists Panel 1, Fuse 7 in the diagram for model year "88, which I believe is not correct. It's been a while since I have worked on this system, so just be aware there might be incorrect information out there.