Hey all. 09 Pontiac Vibe/Matrix 180k. I was told at O'Reilly's that my alternator had failed, but Advance Auto told me it was fine. At both places, it tested 13.7 volts/13.4 volts (accessories on). My OBD says the control module voltage is just over 13 volts. The alternator is not OEM Denso (can't see what brand it is). I've seen other Toyota owners say the Alternator output should be 14.1 volts or higher. I've noticed my car runs great at first, but after long runs with lots of idling, epecially at night with the lights on, it runs a little weird/rough, almost like it's getting tired. Any ideas? Thanks.
Control module voltage 13-13.1 volts alternator?
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JTK
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I'd try to pull over when it acts up hot and measure voltage across the battery at idle to see if it's lower than that ~13.4VDC.
Alternator output should be 14V or more on a nearly charged battery, or disconnected from the battery. Voltage should be measured with accessories OFF, especially the high current ones like radio or lights.
On a weak battery it may be pulled lower and be the battery's fault but if you continue to operate the vehicle like that, it can strain the alternator too. This is on a *dumb* charging system, if your model year has a smart system it becomes more complicated to test in-vehicle because it may reduce alternator output to try to eek out slightly higher fuel economy. Research whether the vehicle has this type of charging system.
After a drive, I'd disconnect the battery, measure voltage with a multimeter while still disconnected, should be around 12.6V. Leave it off and measure voltage again a few hours later to see how low it dropped. There should be very little drop, still very close to 12.6V.
Any idea how many miles and years the battery and alternator have on them? Without more info, I too would suspect the alternator.
On a weak battery it may be pulled lower and be the battery's fault but if you continue to operate the vehicle like that, it can strain the alternator too. This is on a *dumb* charging system, if your model year has a smart system it becomes more complicated to test in-vehicle because it may reduce alternator output to try to eek out slightly higher fuel economy. Research whether the vehicle has this type of charging system.
After a drive, I'd disconnect the battery, measure voltage with a multimeter while still disconnected, should be around 12.6V. Leave it off and measure voltage again a few hours later to see how low it dropped. There should be very little drop, still very close to 12.6V.
Any idea how many miles and years the battery and alternator have on them? Without more info, I too would suspect the alternator.
The control module voltage is 11.9 with the engine off and just above 13 volts while running if that helps
I would go to a good mechanic instead of listening to car parts store employee.
OR did the same to a friend who happened to be a lady. So I told her to go to a mechanic and he told her that the alternator is fine.
He told her that the belt was old and started to fray which was true.
So she changed the belt and never change the alternator and this is already 1 year later.
He did not charge for the diagnosis and she did not even go to him for belt replacement since his shop was too busy.
OR did the same to a friend who happened to be a lady. So I told her to go to a mechanic and he told her that the alternator is fine.
He told her that the belt was old and started to fray which was true.
So she changed the belt and never change the alternator and this is already 1 year later.
He did not charge for the diagnosis and she did not even go to him for belt replacement since his shop was too busy.
^ But it doesn't draw that much current, shouldn't have much wiring drop though maybe some through a protection diode.
I'd directly measure the battery itself to make sure the control module does not encounter some voltage drop, but then the question is whether the battery is bad, not holding a charge, or the alternator failing to charge it. In that case I would use a battery charger to see if the battery takes a charge and results in a higher control module voltage once the charger is done and disconnected.
I'd directly measure the battery itself to make sure the control module does not encounter some voltage drop, but then the question is whether the battery is bad, not holding a charge, or the alternator failing to charge it. In that case I would use a battery charger to see if the battery takes a charge and results in a higher control module voltage once the charger is done and disconnected.
I also don't know how old the alternator/battery are. The battery always tests "good."
Back in the day one of the few differences between the GM car and the equivalent Toyota corolla were the batteries, alternators, and radios.
This actually matters-- this isn't a Matrix/Vibe-- it's a Vibe!
GM, for a while, liked to use the maintenance free batteries, which had a different chemistry compared to regular lead acid batteries, and they needed another 1/2 volt or so to charge right. I think they moved past his with the Vibe, but it's still an interesting anecdote, and important info to note.
What temperature are you seeing when this happens? Heat is supposed to lower alternator output to save batteries.
I would actually stick a new battery in... get a $50 walmart value model. Your old one could be junk but still test good.
This actually matters-- this isn't a Matrix/Vibe-- it's a Vibe!
GM, for a while, liked to use the maintenance free batteries, which had a different chemistry compared to regular lead acid batteries, and they needed another 1/2 volt or so to charge right. I think they moved past his with the Vibe, but it's still an interesting anecdote, and important info to note.
What temperature are you seeing when this happens? Heat is supposed to lower alternator output to save batteries.
I would actually stick a new battery in... get a $50 walmart value model. Your old one could be junk but still test good.
Absolutely true. The op needs to test voltage at the battery not by OBD data for accurate results. The difference between the @Battery volts and the module can be as much as 1-2 volts with engine off due to modules consuming power, lights and ac blower on etc. With motor running the OBD data will usually be within .1-.3 volts of the @Battery reading.
My first thought is the Module has a bad connection.
Clean the battery to firewall, battery to engine grounds first.
Find out where the Module gets its ground remove and clean that one..
Get some Caig Deoxit D5.
Other electrical connector cleaners are good at flushing detritus and old crusty dielectric grease from connectors, but do little to nothing for removing voltage dropping oxzidation from mating conductive surfaces within the connector.
Use both, and the Den-tek mini bottle brushes sold in the dental care aisle of your local drug store can reduce the amount of connector cleaner required to blast the old di electric grease out and the amount of DeOxit required to make the copper/brass/ pins and barrels gleam like oiled gold.
Deoxit D5 on your old Phone's micro USB connector will allow you to remember tht it actually once made a nice clicking noise when it was new when the connector inserted. It Might also charge faster too.
Clean the battery to firewall, battery to engine grounds first.
Find out where the Module gets its ground remove and clean that one..
Get some Caig Deoxit D5.
Other electrical connector cleaners are good at flushing detritus and old crusty dielectric grease from connectors, but do little to nothing for removing voltage dropping oxzidation from mating conductive surfaces within the connector.
Use both, and the Den-tek mini bottle brushes sold in the dental care aisle of your local drug store can reduce the amount of connector cleaner required to blast the old di electric grease out and the amount of DeOxit required to make the copper/brass/ pins and barrels gleam like oiled gold.
Deoxit D5 on your old Phone's micro USB connector will allow you to remember tht it actually once made a nice clicking noise when it was new when the connector inserted. It Might also charge faster too.
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