My Car Won't Start Sometimes Can Anyone Help?

Hello all I can't get my car to start sometimes. This is an intermittent issue that doesn't always happen, it's basically luck of the draw when you turn the key...

Car Model: Volkswagen Tiguan 2011 4WD (Automatic)

Mileage: 170,000km

Dashboard Lights: EPC, Red Battery Symbol, Yellow Engine Light

Issue: Intermittent Car Won't Start

All the cabin lights come on and do not dim, radio works, headlights, etc. We're from Toronto so we had a mechanic on Kipling check the battery, he said it was okay. The car also had some strange noisy, clicking issue for a day when you would change gears, that would make the car slightly shake. Which was when we initially thought to take it in. That gear shift shake went away immediately when he cleared the computer with his reader. But the intermittent issue whereas the car won't start sometimes kept happening. We stopped at a store on Yonge Street one day and turned off the car, it wouldn't start so we left it all night parked outside. My gf took it to a recommended mechanic using a CAA tow truck, while I was sleeping from a long day of work. He checked the car's computer with his reader, said some errors were present and told us he couldn't guarantee the following would work. But to change the "Fuel Pump Sensor" and the "Spark Plugs." As we had purchased the car new and it supposedly hadn't had the spark plugs changed since it was purchased. As a note the "Fuel Pump Sensor" error report was permanently cleared from all future computer read scan reports.

The mechanic called us the next day and said the car was ready for pickup. He warned that the battery might need to be changed, that he charges $300+ for one and recommended that be done soon. We got there and the car was on running... Suspicious because we have never seen a mechanic witness the car not start as the issue is intermittent. And if he knew he didn't fix it, he may have contacted us to come grab it close by while it was running or however he got it going. Not sure as I'm a tech by trade but never learned much at all about cars.

After shelling out $600+ to this mechanic we drove a couple block away, get out for some coffee, come back and the car wouldn't start. It had to be ditched in a parking lot again as the mechanic shop was closed. I call the mechanic the next day he says the car battery was reading 8 volts when he tested it, a pretty low number however my gf had it towed after having the car in a frozen garage all night. He basically said to tackle the battery next... We took public transit to see if we could get the car the next day and luckily it started on first try so I took it to my warm indoor garage. I started losing trust in these guys and started to do some research. After which I took my multimeter and tested the car battery as well as the alternator. Since a group of people I personally trust to know a bit about cars kept saying it could be the battery, starter, alternator, or any other one of the computer errors such as the mass airflow - as some do come up on report. But that it's *most likely the battery, alternator, or starter as per what these group of people say, as the only functionality issue that stops all else from working to drive the car to a destination is "starting up." While all the other errors are likely things that should be handled separately. I should mention when the car starts it NEVER turns off. Ever! You can drive or sit in it without a problem all day...

As I said I don't know everything about cars but I'm a tech so out of frustration and losing trust for mechanics these days I did a battery and alternator test with my multi-meter. The following shows the results of my personal tests as I needed to see something with my own eyes to take further steps before shelling out more $$$. I had a friends mechanic who got him up and running the other day with similar issues swear it was the starter without even looking at the car with 100% certainty. For certain it could be B.S. as I don't know anyone who can declare to have the all knowing mind. It looks like it's more of a process of elimination to make a strict thorough hypothesis, and then declare a repair or replacement be made as per whatever is faulty. My findings after a bit of test research...


Multi Meter Battery Test:
- Stand-alone voltage is 12.46v (after headlights remove trickle charge from alternator to battery)
- Lowest voltage drop (temporary), on ignition key turn start is 11.16v
- Highest voltage increase stays between 13.10v & 13.21v on ignition key turn after 1 minute has passed to let the alternator charge the battery
- 13.15v Steady voltage when all lights, radio, headlights are on. Lowest drop seen on this test was quick and temporary split second 12.95v
- 12.6v is the end result when turning off the car for the battery test in sequence all things above considered.


Alternator Test:
- When directly placing the negative on the battery terminal and touching the body of the alternator with the red probe lead it reads -0.88v, when you rev up it hits -0.93v

According to my findings it appears the battery is okay and the alternator is bad. As the battery should be around 12.6v idle after removing trickle charge from the car during the start of the battery test, never dip below 10v on actual ignition start, and run between 14.2v to 14.7v during ignition start to indicate a healthy alternator. Also an alternator multi meter test I followed shows a normal reading range at -0.05v and mentions to never be close to ONE.



With all this info can anyone concur my findings to indicate the next repair should be the alternator, & that it would likely always start upon replacing or repairing it?

Would appreciate any and all info on this matter.



Thank you so much in advance!

Kevin's 6 years old and we'd like the car to be safe enough to drive and most importantly start all the time! I'll see if I can post a link to my Blue Driver Scan tool's car computer report below as I bought the device to avoid a mechanics constant read and clear codes cost, so we'll only pay them for that if absolutely necessary in the future. I know my last things to check which I can do is to check the connections and wiring from the alternator to the battery for any loose ends, tears, or rips.

 

My hunch is the alternator as well. But I am no mechanic.

 

A corroded negative connection will wreak havoc at times. Alternators usually last 5-7 years tops. Dirty/poor power will "ghost trip" trouble codes due to poor frequency/voltage, especially with sensors requiring a reference voltage or frequency.

I'm starting to think with all the computerization these days, maybe we do need and OBDII category...

 

Get a battery.

 

Don't replace anything.

Find a qualified/certified auto electrician. With the correct meter (not a multimeter) the status of the battery and altenator can be checked in 5 minutes.
Also have the immobilizer checked.

 

Load tester.