missile2511

My blower motor does not come on at all and I was wondering if the missing relay in the photo could be the cause. It is in the center console behind the radio.

Alan

No that is something else - possibly the chime relay.

Check fuses & blower relay - varied by year so you need to help yourself by telling us every single time - better yet - add a sig line with that info. Does the blower blow in the DEF position of the lower slider? Have you checked fuses on CE panel?

Alan

missile2511

Thanks Alan! I will get a tag line put up for this 1984 928 s with a 1983 m28/11 engine. The blower is dead on all settings to include heat, defrost and AC. The fuses appear to be ok, but I do not know how to check the relay.
JOE

Wisconsin Joe

Nevermind, too many differences in the model years for my info to be of any use.

Alan

"The fuses appear to be OK" is a silly answer... they either are or are not.

If you are just looking at them - that isn't good enough. You need a DMM (multimeter) on ohms/continuity test and test them - without that we are all wasting our time. Replacing fuses without knowing if they stay good is similarly pointless. You can also use a DMM in volts mode to see if the fuse is good by testing voltage after it - but you need more understanding of circuit config. for that.

If you don't have a DMM go out and get one right away - you will need it lots. I assume you have the fuse & relay diagram for you model year.

An 84 and 85 are very very different (about as different as it gets) - ignore that.

'Magic Blower' relates to speeds 0-3, if it doesn't work in speed 4 and DEF then you have something else

Check fuse 17 & Relay XXI on an '84 - use the horn relay X in place of Relay XXI to test (same type)

Alan

missile2511

Alan,
This is great stuff. I will pick up my game and test my fuses with my mm. I look forward to swapping the relays to see if I can bring the blower to life.
Many thanks,
Joe

Alan

Check that sig line - "19834"...!

missile2511

The blower relay will sound the horn, but the horn relay will not actuate the blower. The blower fuse tests at 0 ohms.

Alan

OK so next steps - remove the blower relay and look in the socket - can you see 4 terminals located in 4 of the 5 large slots (make sure they look seated properly and not pushed out of the back of the relay socket base...).

The Porsche relay sockets have terminal ID's embossed in the plastic: 1-9 (but not all relay sockets have all these slots).

You need to map relay terminal function to slot location for testing:

For SPST Relays (e.g. 53b type relays as here):

ID R-Label Function
=====================
2 85 Coil (negative terminal)
3 30 Common Switch terminal (usually power in)
5 87 Normally Open(NO) Switch Terminal
7 86 Coil (positive terminal)

ID = the ID embossed on the panel, R-Label is what is probably on the relay itself

Identify the one oriented at 90 degree to the others - this is the 87 terminal (ID: 5) goes to feed the blower - the terminal opposite this one is the 30 terminal (ID: 3) that should be connected to the fuse. Use a DMM in DC volts mode to see that it has ~12v.

Find the coil ground 85 terminal (ID: 2) and use a DMM in continuity mode to check that it is grounded.

With the car ignition on see that you get ~12v in the coil line on 86 terminal (ID: 7).

Report what you find? - you can also plug in a fused jumper between 87 & 30 and see if the blower is activated then - this would also help in diagnosis.

Alan