vanster

Easy to tell if a fuse is bad but how do you detect a bad relay?
My radio and my AC/blower etc have stopped working
I have been chasing this all weekend.

The Forgotten On

Replace the relay with a known working one is the only way I know how to tell a good one from
a bad one aside from energizing the coil.

MainePorsche

Did they both stop functioning at (about) the same time ?
I ask this, for they are 'naturally' unrelated electrically, but because of proximity an 'installer' may have tapped into a switched power line that goes to the blower harness for the radio head. If the blower relay (XXI I think) failed, then both will lose function. Something to consider.

Alan

Well - you can plug it into a relay tester (but realistically nobody has one), you can energize the coil manually and see if it clicks (this is fairly definitive if it doesn't click - but not so much if it does... contacts can still make poor contact.

You can try a fused jumper and see if the equipment runs - if it does - it may mean you have a bad relay contact/coil or could mean an issue with the coil driver circuit (outside the relay)

For common SPST/SPDT relays - replacement with known good ones is the easiest test - not so easy for complex function relays though.

You can test coils with an ohmmeter: expect ~80 ohms anything close is OK (smaller relays will be higher). An SPST/SPDT relay's 30 terminal should connect to the 87a terminal with the coil un-powered and should not connect to the 87 terminal with the coil un-powered. (the reverse when the coil is powered).

In this case test the horn - then if good swap the horn relay for the blower relay (you can then test the horn again? - and the blower)...

This may be the ignition switch - wiggle it about a bit...

Alan

vanster

Yes they both went out at the same time. I am thinking its XXI, not sure what the life expectancy this relay is. One thing about a 928, they get stuffy inside without air or at least a fan that blows.

vanster

This is an '80 which is similar to a Seagull outboard motor, unlike the later cars.
Maybe I should buy a new relay and start from there, however I think the thought of the radio being attached to the hot wire to the blower is possible
I will pull the radio out and see if I can see something obvious

MainePorsche

Yes, I imagine it would. If the Blower Relay is dead, your compressor will not be activated, so no cool air 'dribbling' in even without the fan. The Blower Relay is in the power path to the compressor clutch.

MainePorsche

The power line to the fan switch is a red/white wire.

Pyzik

You can use a 9v battery and touch It to the coil leads, and it should click