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Discussion Starter · #1 ·
Hi,

1st post! Got my 2007 XC90 V8 Sport last March and love it! Have already gotten great help and advice from posts on this forum - thanks!

Looking for some help with this one...

Loaned my car to some relatives to drive from Boston to Florida over the holidays. Car died on them in Virginia day before Christmas Eve. (Power system service urgent). They said car was acting funny and running hot (they know nothing about cars).

AAA towed it to local mechanic shop and they diagnosed and replaced the alternator. After replacement the warning would not go away but charging was verified ok so they took the car and drove it the rest of the trip.

When relatives returned the car to me, they told me that the warning light was still on. I contacted the mechanics shop that did the work and they gave me the P/N of the alternator they put in and said they were aware that maybe they used the incorrect alternator having the internally controlled voltage and current.

Strange that the alternator number they said they installed (no-name equivalent to Bosch AL0854X) doesn't even look like it would fit.

Anyway the shop agreed to send me a replacement (Bosch AL0821X) at no charge.

This weekend I swapped out the alternator put in by the shop with the replacement AL0821X and the warning message will not go away though the car seems to be charging ok.

Any suggestions what to do next?

Thanks!

Greg
 

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Someone far more familiar with this issue can chime in. If it were me, I would be inclined to find an individual or a shop with DICE and VIDA and let them take a look. There's some good information on the second link (post #14 onwards) about communications between the ACM and the ECM but you'll need to get the right diagnostic tool (Volvo specific) to get a level of detail that might be meaningful. Could also try and PM garbergtsi to see if maybe he can walk you through some troubleshooting. Best of luck with getting this resolved.

Go Hawks!
 

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2008 Volvo S80 V8 AWD "OEM+"
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Are you certain the correct alternator was used? Many parts systems list the earlier non-computer controlled alternator when really the car should be using the computer controlled version. This is what would happen if you used the version that isn't computer controlled.
 

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Are you certain the correct alternator was used? Many parts systems list the earlier non-computer controlled alternator when really the car should be using the computer controlled version. This is what would happen if you used the version that isn't computer controlled.
BUT....the V8 never had a standard regulator, it always used the ACM style that comms via LIN.

AL0821X is correct, that has been a pretty good alternator...i do tech support for bosch and its quite uncommon to have a problem with that unit
 

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Discussion Starter · #7 ·
Update:
So I took the XC90 in to Boston Volvo today and paid for a diagnostic.

Their verdict: "We tested - Has proper voltage coming out on LIN bus line and we have proper voltage - Has direct line from LIN bus to alternator. Needs alternator".

So, I then called Bosch tech support and spoke with someone to double check the application and try to get any more info. Bosch tech support said AL0821X is the only (and correct) alternator and the likelihood of the remanufactured alternator is bad is unlikely.

My next step I guess is to check the LIN bus myself. Bosch tech support said to disconnect small wire on alternator and measure voltage. It should be between 7V and battery voltage, and to check the square wave pulses with a scope (dealer wouldn't check waveform).

I found this thread with some more info. http://forums.swedespeed.com/showth...placed-on-2005-v8-Power-System-Service-Urgent

Questions:
If I measure the correct voltage on the LIN bus wire and I see a square wave. Does that 100 percent rule out the ECM and confirm the alternator is bad?
Any other way to verify its the alternator and not the ECM?

Thanks!
Greg
 

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Hey, dude from bosch here. If you have square waves that pretty much eliminates the ECM as being an issue. The way the Lin bus works is each (master and slave) control module sends out a reference voltage 1-2v under b+ and the master cm initiates communication by grounding that reference voltage in a series of quick pulses. The ACM then responds with a series of quick responses (pulses to ground)
Usually when an ECM goes bad, it had odd voltages on the top or bottom of the voltage range.
 

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Discussion Starter · #10 ·
So - to follow up... Installed a 3rd alternator and still the same thing. Warning light still on. Sent ECM to Xemodex and they verified LIN bus needed repair. Thanks for help and info!
 
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