AndyBees
Top Post Dawg
- Joined
- May 27, 2003
- Location
- Southeast Kentucky
- TDI
- Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
As the title says, ALT output fluctuates between about 12.5 to 15.5 volts (read more). (2001 Jetta, 410k miles, Bosch reman, 120amp ALT)
Background, the car was brought to me several days ago. The owner said it did not start good and that he had installed a new battery. The battery is from Walmart and completely fills the case. I never bothered to look for the amp rating. It does have a 10/18 sticker on it. Also, due to personal issues, I let the car sit for several days before starting it to do diagnostics. I noticed that the RPMs appeared to be going up and down a wee bit. But, by the time I got VCDS connected, the engine had smoothed out. The only DTC was for the CTS.
Anyway, the above was several days ago. So, last evening the engine barely started. I moved the car inside my garage and installed a new Coolant Temp Sensor. Then I left it with a trickle charge on until this morning. A few minutes after removing the trickle charge, I checked the voltage, 12.5. But, the engine did start okay in my 60f garage.
So, anyway, the fluctuation in voltage causes the engine RPMs to noticeably change and I noticed the Serp belt/Tensioner acted as if it was pulsating. I'm assuming the higher volt out-put is causing a slight drag on the engine so it compensates to keep the RPMs constant. (nothing on and park brake up)
Interestingly, after a few minutes (2 or 3) the ALT settles down and shows 14.3 volts and the Serp belt is as sooth as silk. I shut the engine down and restarted, again 14.2 volts and no pulsating. I waited a three or four minutes and restarted, again 14.2 volts and no pulsating.
I did install a new ALT pulley (INA) last spring on this car.
I'm letting it sit outside the garage and cool down to ambient (19f here at the moment). I plan to start it later today to see results.
So, any thoughts about what might be going on?
Background, the car was brought to me several days ago. The owner said it did not start good and that he had installed a new battery. The battery is from Walmart and completely fills the case. I never bothered to look for the amp rating. It does have a 10/18 sticker on it. Also, due to personal issues, I let the car sit for several days before starting it to do diagnostics. I noticed that the RPMs appeared to be going up and down a wee bit. But, by the time I got VCDS connected, the engine had smoothed out. The only DTC was for the CTS.
Anyway, the above was several days ago. So, last evening the engine barely started. I moved the car inside my garage and installed a new Coolant Temp Sensor. Then I left it with a trickle charge on until this morning. A few minutes after removing the trickle charge, I checked the voltage, 12.5. But, the engine did start okay in my 60f garage.
So, anyway, the fluctuation in voltage causes the engine RPMs to noticeably change and I noticed the Serp belt/Tensioner acted as if it was pulsating. I'm assuming the higher volt out-put is causing a slight drag on the engine so it compensates to keep the RPMs constant. (nothing on and park brake up)
Interestingly, after a few minutes (2 or 3) the ALT settles down and shows 14.3 volts and the Serp belt is as sooth as silk. I shut the engine down and restarted, again 14.2 volts and no pulsating. I waited a three or four minutes and restarted, again 14.2 volts and no pulsating.
I did install a new ALT pulley (INA) last spring on this car.
I'm letting it sit outside the garage and cool down to ambient (19f here at the moment). I plan to start it later today to see results.
So, any thoughts about what might be going on?
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