QuestionHi there!
I have a 1997 VW Passat GLX 110,000+ miles. Recently I have noticed that sometimes the car starts with a rattling noise and then the engine dies out. The alternator light comes on, but then when I start again and press accelerator for some time the engine stays on and the alternator light goes off. I can now keep the car engine on without pressing on the accelerator. I can also switch off and start again without any problem. However, just while releasing the accelerator the engine slows down (obviously!) and the alternator light comes on momentarily and then goes off.
I recently only have purchased this car (my first) and I have very little knowledge about car maintenance. I live in a upstate NY and it's cold in winters. So I used to put the heater at maximum heat as soon as I entered the car, my friend told me that since we are only using heat from the engine batteries are not involved in heating the car. However, now another friend on mine told me that they are involved in heating the car, and due to my bad practice of making a sauna inside car, the batteries might have died out. I had read on the internet that starting problems are usually related to alternator, also alternator light comes on when starting the car for the first time in the day. Also, I should add that sometimes the car did not start I had to jump start it. So I am confused whether it is the alternator or the batteries. Also, I have heard that replacing the alternator is very expensive (~$700), I am scared.
Please advise this first time ownwer. Thanks
AnswerHi Tamanna,
I appologize for the late reply to your question, but since it is a complex problem, I wanted to make sure I was able to give you good advice. I'm also assuming you have a gasoline engine and NOT a diesel.
OK. It does sound to me like your battery is weak but it may be an effect of a poorly-working alternator. Your battery is ONLY used as a kinetic energy source to START your engine. Once the engine is started, the alternator is supposed to start operating and supplying power to the accessories you are using as well as top-off the charge in the battery and power the engine management systems. When your charge light is lit, the alternator is not supplying the needed power, instead the battery is what is running the accessories as well as the EMS. So, I'd have to say that would be pretty accurate to say that the reason your battery is going dead or running on low-charge is because the alternator is not supplying the correct amount of power while the engine is running.
You state that when the engine RPM's are higher (off-idle) the alternator light goes off. If this is the case all the time, then I'd say that the idle-speed of the engine needs to be increased. Since your vehicle is fuel injected, I'd have to point my finger at the IAC (Idle Air Control) Valve. That is what controls idle cold or hot. It sounds like it is working, to some degree anyway, so my 'guess' would be that the pindle and/or seat is blocked or has too much carbon built-up on it causing the valve to not fully close or open which would be a problem that would cause erratic operation of the engine mostly at idle.
$700.00 to replace the alternator? Awesome. You must have gone back to the dealership to get a quote like that. I could quote you on a good, used alternator for probably around 10% of that but I need to know more about your vehicle, probably things you would not be able to answer. I'm not patronizing you Tamanna, but the question I'd need answered is: what is the amp rating of your alternator, 90 or 120 amp?, I'm sure you'd be able to answer the engine size question (4cyl or 6cyl).
My advice on finding a good technician: Steer clear of the dealership as well as 'chain' stores like Firestone, Sears, Pep Boys, Monro Muffler/Brake, Midas, etc. as they usually only employ ONE ASE Certified Tech just so they can say they do and chances are, that guy is the asst. manager or manager and is not in the store to diagnose/repair vehicles anyway. Find a service location in the link below or get some names out of the yellow-pages and do a drive-by. Garages that employ ASE Certified Technicians will be marked with the 'Blue-Seal' insignia. If unsure about whether a place employs Certified Techs, just ask to see their credentials. ALL ASE Certified Technicians will be PROUD to show and display their certificate(s).
Thanks for the question, I hope this information was helpful to you.
Fred
www.knucklebusters.us
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