Magnus 928S4

After some troubleshooting, I've been running my 88 when I jump relay XXV.
Relay is ok I've swapped with other.

What can be wrong?

WallyP

Pull the relay, and identify the terminal in the socket.

Check Terminals 30 and 86 for 12 vdc. If there is no power on 86, the problem is a faulty connection from Terminal 30 to the power connectors (30 bus) on top of the Central Electric Panel.

Terminal 85 should be grounded thru Terminal W21 (bottom right terminal in Plug W, brown/white wire) to Terminal 21 on the LH Control Unit when the engine is running.

Magnus 928S4

What could interfere relay XXV that makes it not to close, immobilizer some senor like o2, temp II or other?

SQLGuy

As Wally pointed out, wiring problems could interfere. What did you find in your measurements?

Another check you could make is to see whether you have 12V on pin 21 of the LH connector - open the headshell so you can verify the voltage at the pin under conditions where the relay should be closed. Normally the LH unit should be pulling this pin low in order to close the relay. If you read 12V (high) here when the relay should be closed, then the problem is probably in the LH unit itself. If you read 0V (low) here, then there's a wiring problem somewhere.

Landseer

Dirty grounds at base of engine valley will cause intermittency at XXV also.
And, the rest of the critical electronics share those grounds.
Wally is celebrating tonight, he'll be back I'm sure to help you further.

Magnus 928S4

There is no power when i check 30 and 86

Alan

That is very odd - are you sure:

1) You are testing it right - what are you doing exactly (what was your ground?)

2) That you are looking at the right relay - look at the arrows next to the labels...

Alan