Porschedrsmith

1986 PORSCHE 928 S2
Heater blower not working.
Relay seems ok.
If i put a jumper wire between pin 30 to 87 the blower works on all speeds.
when put relay back doesn't work.
Anyone got any ideas please.

Mrmerlin

Did you put a different relay in for the blower ?
Have you verified that all the other relays in your CE are the correct ones and in the correct positions?
Did you replace the X bus relay?

Porschedrsmith

YES I TRIED A FEW DIFFERENT RELAYS THAT I NEW WORKED.
ALL OTHER RELAYS WORK FINE.
WHAT IS THE X BUS RELAY.Thanks

Zirconocene

Scroll down for 1986: https://928srus.com/pages/charts

Looks like Relay 4 is your X Bus relay.

Cheers

Porschedrsmith

The x bus relay is ok

Mrmerlin

to be clear,
have you verified that the correct part number relays are in the correct positions on the CE panel ?

Porschedrsmith

Yes all relays in right place

Mrmerlin

NOTE disconnect the battery first.

OK look along the bottom edge of the CE panel for loose connectors,
and or individual wires that have come free .

next drop the CE panel and look for wires that might have gotten hot,
NOTE the insulation will have a satin finish instead of Matte.

Porschedrsmith

Front and back of fuse board all the wires ok

Alan

HVAC head unit unplugged?

Alan

Porschedrsmith

The HVAC is all plugged in. Thanks

Alan

The HVAC head unit is what turns on the Blower Relay - it is powered through Fuse #8.

Alan

Porschedrsmith

Thanks
When i jump 30 -87 the four speeds work on the head unit doesn't that make head unit plugged in.

Kevin in Atlanta

First, are you getting voltage from the HVAC to the relay with the blower on?
Next, test the ground at the relay.

Either of those should point you in the correct direction.






Kevin

Alan

No it proves rather little about the head unit - it does mean the blower speed switch is plugged in but that is a completely separate connector from the main HVAC one that turns the relay on - check the fuse #8 - that was my point, A blown fuse would stop the relay turning on normally.

With the Blower Relay (X) out you can see if pin 86 in its socket is at 12V with Ignition on and HVAC head not turned off (blower switch doesn't matter), you can also test that socket pin 85 has continuity to ground. These are the only things needed to turn the relay on. Likely you don't have 12V on 86. NB For this year the X-Relay (IV) is not a factor

Alan