O2 Sensor Relay + Freq Valve problems
 

My 82 SC O2 sensor relay is not behaving correctly and the frequency valve will not work.

I've tested with 3 different new relays with the same results. Also, the frequency valve and new O2 sensor are within spec.

With the engine OFF. The relay gets voltage at terminal #30 (12.3V) and at #87a (12.3V). #87 gets nothing.

With the engine RUNNING #30 gets 13.7V, #87a nothing, and #87 13.7V. And of course the frequency valve will not function.

With the engine off, I use a jumper wire from #30 or #87a to #87. Freq valve comes alive. Drives beautifully. But when I shut off the engine the frequency valve stays on I have to pull the relay or the harness connector on the freq valve. To get the valve to function again, the relay needs the jumper wire.

Any ideas on what is causing this? :confused:

u must use the correct porsche relay, those uni 5 blades will not work good, also, pull your seat and u will see your grounds for the lamda control unit, there are several, i clean my grounds with sand paper, and apply di electro grease.

Thanks. I'll clean those grounds up. I'm using a new Wehrle W. Germany relay that looks identical to the original Bosch, I thought that would work. I'll pick up an OEM one.

This is going to sound stupid...but does your dome light and clock work? The fuse that these items are on, also provides power to the lambda brain. So if it's bad, replace it.

Lights work and fuse #18 is good. I opened up the brain, the board looks good and it's getting power.

hook the jumper to power with key on only, if you have to drive it until you get a decent relay.

part # 821-951-253-m14...14 bucks from pelican

ahh, nice tip. I'll use this until the correct relay arrives. Thanks.