How to test LH System Relay -> Bentley WRONG

[PianoDavid]

(this was included in another one of my threads recently but, being unanswered, i believe it deserves its own.)

Does anyone know how to test the LH System Relay THE RIGHT WAY? In the Bentley manual, instructions start out with "Connect pin 21 on the LH control unit connector to ground." But pin 21 is switched battery voltage - I checked 12.64V)! Why the hell would you connect that to ground? Well I did it before not knowing what that pin was and you know what happened? It blew fuse #22 (relays & ECU fuse)! This was found in "Fuel Injection 240-11"

i've come to the conclusion that these instructions are inherintly wrong, and i am wondering if anyone has maybe a diff. (new, updated?) version with different instructions.

[A. Nijhof]

According to the Bentley wiring diagram on page 371-65, connecting pin 21 in the ECU connector to ground will switch the main relay.

Did you remove the main relay and checked the coil for short circuit?
These are common relay's so try another known good one.

What's the reson for checking the main relay?

[PianoDavid]

Originally Posted by A. Nijhof

What's the reson for checking the main relay?

the car will no longer stay running - this after i severley damaged my AMM (put a new one in though!). check my other post if you want the full story - its sorta complicated.

LH 2.2 System Issues - won't stay running.
http://www.saabcentral.com/forums/sh...ad.php?t=69251

[Willy Wonka]

Dave,
Pin 21 of the ecu has a (1) yellow and white wire on it. Be certain you have the right connector terminal. Test for continuity ( 0Ω ) between it and main relay pin 85.
The reason it has 12 volts on it, is that it (12v) comes from the battery to the relay coil to the ecu. It gets grounded by the ecu to switch the relay on. It's on pin 21 that you should see the voltage change as the relay gets switched on by the ecu.
Check what's connected to the fuse that blew.

[PianoDavid]

ok so today i plugged in the second hand relay i bought off ebay, bosch p/n 0332015006 - which is what eEuroparts.com said i needed for my specific car's LH System relay. well first of all when i plugged it in there was no difference b/t mine and the 2nd hand one (suposedly working). second, they are different part numbers. the one i bought ends with 5006 however the ones in my car end with 5013 (bosch# 0332015013). so i thought maybe the relay i had purchased wasn't working correctly b/c of this descrepancy, so i switched my fuel pump and LH system (same Part No.s) because i figured even w/o fuel pump it would idle fine (at least for 5-10 seconds for this test).

in the end no combination of relays made any difference so i now believe my relay is fine. engine died after 5-7 seconds of running and RPMs are all over the place. ex: 1000>12000>500>dead

Originally Posted by A. Nijhof

Did you remove the main relay and checked the coil for short circuit?

How would i check the coil for short circuit? relay=unplugged coil=+terminal voltage=good??? or voltage @ +terminal=short circuit?

Originally Posted by Willy Wonka

Pin 21 of the ecu has a (1) yellow and white wir. Be certain you have the right connector terminal. Test for continuity ( 0? ) between it and main relay pin 85.
The reason it has 12 volts on it, is that it (12v) comes from the battery to the relay coil to the ecu. It gets grounded by the ecu to switch the relay on. It's on pin 21 that you should see the voltage change as the relay gets switched on by the ecu.
Check what's connected to the fuse that blew.

I will check for continuity tomorrow, and to make sure i have the correct terminal/wire color; however, i do not understand how 12V would go from battery-->coil-->pin 21. because if pin 21 was then connected to ground it would short an blow a fusewould it not? maybe i don't fully understand relays . The voltage on pin 21 should change? from 0--> 12V i assume?

Bentley manual says to connect 21->ground and that 12V should be present at termnial 9. should they both have 12V ??? sorry im very confused about all this (except about checking terminal/wire color ) how do i check what fuse#22 is connected to? The fusebox says it powers the Relays and the ECU. Or do you mean physically follow the wires? UGH that'd be a pain!

[PianoDavid]

The diagram in the bentley manual is drawn from the BACK of the connector - though this is not mentioned ANYWHERE on the page.

i found this outo because i saw a diagram on another page (later in the manual) that said it was from the back, and it was the exact same diagram, same pin#s and everything. - in my opinion, that REALLY should've been stated in the caption to that diagram.