Power System Service Urgent Message??Not Charging What Gives??

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EuroC30NY E Hello guys, I am hoping someone here could help me narrow down my issue.I am having a problem with my 2007 volvo xc90 v8 4.4.I am getting power system service urgent message.I know that the alternator is not charging.So before you say anything let me give you the back story.Last year I had the same message.I had the alternator replaced by a mechanic.After replacement the car ran and was charging at 14.3volts hwoever the message was still on.The mechanic gave me the run around saying the system had to reset.So instead I took it to a friend of mine who works for Audi. He had told me that most likely the mechanic installed the cheaper alternator thats self regulating and that I need the more expensive one.But he can get mine rebuilt for a small fee.So long story short i had it rebuilt.Truck ran fine for about 3 or 4 months.Then the problem returned.Same thing again. However now the truck is not charging again. battery is at 12.24 volts.With the truck running it drops below 12v.So its not charging.I've done some research on these common problems on these trucks.It seems as if the LIN wire going to the ACM could be my issue or the ECM.So I've done the following.I know the Alternator is not iso maybe the rebuilt was ****???Needs another alternator???Anyways here is what he found: LIN wire connected to ACM , key on engine running i see 7.24vdc and slowly dropping.Once the warning is on i only see 7.10vdc Next LIN wire connected to ACM, key off engine off 7.54volts shown. LIN wire disconnected from ACM, key on engine running shows about 8.00vdc and drops to about 7.90vdc LIN wire disconnected from ACM , key off engine off shows 8.30vdc. So the obvious is I need another alternator or a new one correct??? Is there anything in that circuit that could cause the alternator not to charge at all??I've read a few things about the charging circuit in the ecm being the weak point and not being able to handle the voltage???At this point my friend has the car.He thinks a new alternator is needed or at least a voltage regulator.I just want to be sure were not missing anything.Fuses near the battery have been checked and are all good.Is there anything else that could be the cause like a ECM????Any help is greatly appreciated. #1 · Apr 21, 2018 Hello guys, I am hoping someone here could help me narrow down my issue.I am having a problem with my 2007 volvo xc90 v8 4.4.I am getting power system service urgent message.I know that the alternator is not charging.So before you say anything let me give you the back story.Last year I had the same message.I had the alternator replaced by a mechanic.After replacement the car ran and was charging at 14.3volts hwoever the message was still on.The mechanic gave me the run around saying the system had to reset.So instead I took it to a friend of mine who works for Audi. He had told me that most likely the mechanic installed the cheaper alternator thats self regulating and that I need the more expensive one.But he can get mine rebuilt for a small fee.So long story short i had it rebuilt.Truck ran fine for about 3 or 4 months.Then the problem returned.Same thing again. However now the truck is not charging again. battery is at 12.24 volts.With the truck running it drops below 12v.So its not charging.I've done some research on these common problems on these trucks.It seems as if the LIN wire going to the ACM could be my issue or the ECM.So I've done the following.I know the Alternator is not iso maybe the rebuilt was ****???Needs another alternator???Anyways here is what he found: LIN wire connected to ACM , key on engine running i see 7.24vdc and slowly dropping.Once the warning is on i only see 7.10vdc Next LIN wire connected to ACM, key off engine off 7.54volts shown. LIN wire disconnected from ACM, key on engine running shows about 8.00vdc and drops to about 7.90vdc LIN wire disconnected from ACM , key off engine off shows 8.30vdc. So the obvious is I need another alternator or a new one correct??? Is there anything in that circuit that could cause the alternator not to charge at all??I've read a few things about the charging circuit in the ecm being the weak point and not being able to handle the voltage???At this point my friend has the car.He thinks a new alternator is needed or at least a voltage regulator.I just want to be sure were not missing anything.Fuses near the battery have been checked and are all good.Is there anything else that could be the cause like a ECM????Any help is greatly appreciated. See less See more Sort by Oldest first Oldest first Newest first Most reactions #2 · Apr 22, 2018 At this stage you need to diagnose with VIDA (and not with some generic code reader) VIDA will communicate with the alternator and tell you what is wrong The Alternator is an intelligent alternator that reports it's current charging current to the CEM, and thus also to the diagnostics system The diagnostics can run a few tests on the Alternator, such as testing the alternator voltage output vs temperature compensation, to make sure all is working well. Don't start replacing parts blindly hoping you will get lucky. Apply the proper diagnostics methods using the proper tools and you will save youself a lot of time and hassle and likely money as well. #3 · Apr 22, 2018 Aside from the above I think I would remove the alternator and have it tested at a shop with the appropriate equipment to do so. When a serviceable alternator goes in I'd monitor the temperature of the thing to make sure it doesn't get too hot indicating a possible excessive draw somewhere. #4 · Apr 22, 2018 Check the t-joint connecting the windshield sprayer hoses. If it's leaking I would just assume the alternator's bad. It's a common enough problem that I would feel comfortable just going for it. #5 · Apr 23, 2018 Your voltages on the LIN wire appears to be correct. You more than likely have a bad alternator. The LIN voltage is typically 2-3V less than battery voltage. There is a likely hood that alternator did not have the correct regulator to begin with. US markets and maybe one other use the LIN bus, all other markets use a conventional regulator. You could possibly just replace just the regulator but between the labor and the cost of a new regulator a new alternator would be cheaper. Get the Bosch alternator, it's a 180A, Volvo P/N is 36000791 or Bosch is AL0821X. #6 · Apr 24, 2018 Generally speaking, one of the areas where Volvo messed up with the numbers and item variation on these cars is the alternator. Way too many changes from year to year, model, and so on. Try first searching on those online sites which regulator should be yours - for your year and engine. FCP is good in that it shows the compatible cars, but even then take the info with a grain of salt. I am under the impression your friend actually doesn't really know about this, so I'll wait for now and not go with his recommendations. The better approach would be to source a used alternator from a V8 for Ebay and hopefully from around the same year. It shouldn't cost more than $200, perhaps quite much less. What I've learned is that many don't understand that these cars want the alternator - and in particular the regulator - that the car came out from the factory. If you just search online you'll notice how many part no. for these regulators exist out there. By all means use only Bosch if that was the original part. However, before going for another regulator, I'd pay some money and do as suggested above, have the car diagnosed with Vida. Local advertising sites may help find a Volvo tech that works from his home and can help with this. Keep in mind, there is always a possibility of a parasitic drain (a switch or module that has a short). #7 · Jun 20, 2022 Hi @OP - how did your car end up getting fixed? I just got the same car model (2007 V8) and the same problem! I said to my local Indy who specializes in Volvo diagnosis that I want a new alt installed - but he keeps telling me do more tests and it could be the ECU… drives me nuts 🌰 #8 · Oct 4, 2025 Hi all, no had the same issue on a customers car two alternator into the job. Multimeter was showing increased voltage but actually the scan tool wasn't picking up any voltage from the alternator. I came across this post and what I basically did was change out the regulator from the original to the aftermarket one and hey presto... FIXED. Warning gone. Hope this is a quick and cheaper fix for some of you out there experiencing the same issue Insert Quotes Post Reply

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