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Jetta loses all power when I turn the headlights on.
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deboe
New User
Aug 20, 2017, 9:30 PM
Post #1 of 10
(2331 views)
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Jetta loses all power when I turn the headlights on.
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2008 Jetta City. 2.0 L 190,000km
While I am driving, turning on my headlights causes my car to lose power. When I turn the headlights on my RPM's drop fast and I cannot accelerate for 5-6 seconds, causing a "limp" mode. After this time period the car "catches" and accelerates as normal.
The funny thing is... if I hold the high beams on the car acts normal. The problem only happens when I turn on the headlights.
If I change gears during the "limp" time, the car "catches" and reacts as its supposed to.
The headlights do not cause an issue when the car is not moving. It only happens when I am driving.
Any suggestions / recommendations would be greatly appreciated
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 21, 2017, 4:50 AM
Post #2 of 10
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Re: Jetta loses all power when I turn the headlights on.
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This just smacks of a weak/missing ground problem. Since it seems intermittent or can correct isn't going to be that easy to know for sure just what or where. Radiator supports should be totally grounded to the rest of metal body might be places elsewhere that does that - they are all over vehicles on purpose so things work and static controlled too.
Different ways - real bare wire braided straps or other manner. Just adding those out of any harm's way is OK metal to metal just know it all begins at engine blocks direct to negative battery posts.
Anything electrical makes a loop out and back to battery no matter what the item is consuming electricity,
T
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Hammer Time
Ultimate Carjunky
/ Moderator
Aug 21, 2017, 4:58 AM
Post #3 of 10
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Re: Jetta loses all power when I turn the headlights on.
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I would agree with tom. Sounds like a ground issue.
Was anything done to it recently that could have triggered this.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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deboe
New User
Aug 21, 2017, 8:35 PM
Post #4 of 10
(2280 views)
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Re: Jetta loses all power when I turn the headlights on.
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Thanks for the answers guys. I installed a new fuel pump about a month ago.
I just measured the battery.
Car not running: 12.67
Car running: 14.05
Headlights on: 13.80
High Beams on: 13.83
A/C, Wipers, Signals, Headlights on: 12.35
Keep in mind the problem happens when I am actually driving the car.
My uncle tried the old take the negative battery connection off while its running to test the alternator. The car kept running when he did.
Can I check for bad grounds by myself or do you recommend a mechanic?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 21, 2017, 11:47 PM
Post #5 of 10
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Re: Jetta loses all power when I turn the headlights on.
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It's been damaged now by running it with a battery cable disconnected and running. That is now 1st to chase down the extent and find the dang ground that's at fault.
That test for a charging system is older than dirt back to generators nothing out there has a generator anymore since the 1960s! Keep anyone who thinks that way away from you vehicle.
Add grounds this is now how headlights get grounded now who knows what control devices were ruined by running it without cable connected! OMG a disaster on top of a disaster,
T
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 22, 2017, 4:04 AM
Post #7 of 10
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Re: Jetta loses all power when I turn the headlights on.
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HT - make that 50 years ago not sure when last generator was used! We are still hearing of this trick wasn't good then either. Now as HT said whatever was the problem with this car this is THE problem to deal with and wont like what it's going to take to undo that then still find the problems you came here for,
T
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Discretesignals
Ultimate Carjunky
/ Moderator
Aug 22, 2017, 5:49 AM
Post #8 of 10
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Re: Jetta loses all power when I turn the headlights on.
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Why would you pull the battery cable off anyway if you have a volt meter? I've taken a few ECUs apart and they do have surge protection and polarity protection, but it isn't something you want to test.
The vehicle isn't sold here in the states and don't have access to wiring schematics. Maybe you should take it to a reputable VW mechanic.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Sidom
Veteran
/ Moderator
Aug 22, 2017, 2:21 PM
Post #9 of 10
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Re: Jetta loses all power when I turn the headlights on.
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For future reference...
measure engine off volts........12.67v....when started the reading needs to be higher than this....
engine on.......................14.05v.....this reading tells you your alt is working...then load the system and expect a slight drop
Loaded.............13.83v........it's lower but well above off volts...so we are good
Heavy load..........12.35v.....look at the off volts......this is a problem...could be a weak alt or wiring problem, ground prob or even a bad battery... Have the battery tested and then google.....voltage drop testing.....This will help you find excessive resistance in the wiring, whether its on the power or ground side..
As the others have said,,,,,removing a batt cable while the engine is running is a bad idea..... It's a DIY trick and the problem with it is...bad things don't happen every single time someone does it....So you will hear.....That guy is full of it....I've done that dozens of times and never had a problem...but all's it takes is once under the right conditions to do thousands of dollars of damage in seconds....
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deboe
New User
Aug 23, 2017, 5:04 PM
Post #10 of 10
(2213 views)
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Re: Jetta loses all power when I turn the headlights on.
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thanks so much for your help. I will do just that.
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