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Old 02-22-2015, 09:55 PM
1 posts, read 701 times
Reputation: 10


My mom has a 2004 forester, her car keeps having problems starting after she has used the lights or air conditioner. She has replaced the battery,spark plugs,coil and the alternator. Twice everything test good but when she has had to use her lights after she turns her car off it will not start again. What else could this be ?
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Old 02-23-2015, 05:18 AM
26,163 posts, read 14,457,966 times
Reputation: 17235
Welcome to the site

That happend to me and my dad one day..... We were waiting in a parking lot and had the radio on (Lights were on also) for about 20 minutes.. When we tried to start it,IT WOULDNT TURN OVER!!

It was a big deal but we finally got a jump!! -- FROM MY MUM!! (Thankfully she was home at the time)

Good luck buddy......
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Old 02-23-2015, 05:56 AM
Location: In the Hood, Brooklyn, NY
362 posts, read 697,749 times
Reputation: 389
Should this thread be here in Movies?
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Old 02-23-2015, 06:16 AM
26,163 posts, read 14,457,966 times
Reputation: 17235
I have already asked for it to be moved.. (I didnt wanna mess it up so I silently reported it to staff and asked it to be moved to the automotive base)

Now this thread is all messed up
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Old 02-23-2015, 03:51 PM
20,304 posts, read 37,790,850 times
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Originally Posted by akatrk View Post
Should this thread be here in Movies?
No. I'll move it to automotive for the OP.
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Old 02-23-2015, 03:53 PM
Location: Ohio
780 posts, read 2,134,790 times
Reputation: 628
Hmm, where do I start ...
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Old 02-23-2015, 04:17 PM
Location: Chicago - Logan Square
3,396 posts, read 5,973,012 times
Reputation: 3705
Originally Posted by POS VETT View Post
Hmm, where do I start ...
You start with the wires attached to the first headlight and keep going, and going, and going....

I suspect a short in the wiring for the headlights and air conditioner, the only solution is to track it down. To do that you need to look at the wiring diagram for the car to isolate areas that the systems share and then inspect those. You could also just take a quick look at the obvious connection points for the systems in question and hope you see an obvious problem. If not, you either have to really start digging around to trace the short or pay someone else to do it.
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Old 02-23-2015, 08:52 PM
4,762 posts, read 10,228,445 times
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If the car does not have an instrument cluster voltage gauge, get a cigarette lighter plug in voltmeter like this...

Amazon.com: LCD Cigarette Lighter Voltage Digital Panel Meter Volt Voltmeter Monitor for Auto Car Truck (1piece): Automotive

Keep an eye on that gauge when driving around.

When the alternator is charging the battery, the voltmeter should indicate 13/14 volts. If it is frequently indicating 12 volts or less, then the battery is not being charged. More likely to happen when the car is stopped at stop lights...

If that is the case, then the alternator may need to have its belt tightened. Or if there is a voltage regulator separate from the alternator, that could be bad.

And there can be loose/dirty main electrical cables. INCLUDING THE MAIN GROUND CABLE TO THE BODY AND ENGINE!!!! Do a "voltage drop test" to find those problems...

(Search google.com for automotive voltage drop test.)

The right way to test this would be to use a clamp amp meter to measure amperage draw with the lights and A/C on, then see how much amperage the alternator is putting out. A DC clamp amp meter like the following (not sold in automotive stores because theirs only measure 10 amps!)

Be SURE it says it will measure 600 amps DC current!! (Deceptive advertising with models which measure 600 volts DC, but only 600 AC amps! [house electricity, not car])

Note the 640 model difference!

Last edited by Billy_J; 02-23-2015 at 09:35 PM..
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Old 02-23-2015, 09:28 PM
10,869 posts, read 41,139,178 times
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Highly unlikely that either the headlight circuit or the A/C system both have a short in them. Typically, if they have a "short" in them drawing excessive power, the fuse(s) for these items will blow and shut them off.

More likely is that the alternator is not producing or delivering enough power to the electrical system to meet all the demands of the car. The marginal difference of using one or both of the auxiliary systems is enough to draw down the battery while driving so that it doesn't have enough power to restart the car again. It is significant that you have identified that the starting problem originates with using those heavy power consumers but is not a problem when your Mom doesn't use those items.

So the problem becomes one of isolating where the electrical deficiency is in the system.

It could be a defective alternator/regulator, or it could be in the wiring between the alternator and the battery.

You'll need to have the alternator full field output tested for the max output to be verified within specs. Even though the alternator has been replaced, it may be defective.

Then you'll need to have the wiring checked. There could be poor grounds/connections in the engine compartment which will contribute to poor charging/starting problems. Or there could be poor wiring/connectors on the alternator output to the battery connections. Or the battery cable ends at the battery could be dirty or not making good connections.

While a competent auto tech can verify all of the system voltages and normal amperages, and verify the connections using a voltage drop test at each site ... a prudent tactic would be to simply start cleaning up all of the ground wiring connections underhood. Subie has a bunch of them to the engine and the body/chassis, all of them are important to the proper functioning of the car. As well, cleaning up and verifying the integrity of all the "hot" wires/connections underhood is critical, too.

At that point, a tech can verify that the battery, alternator, and starter are all performing within specs and then verify that the alternator can keep the system voltage up and charge the battery while supplying all the needed electrical power to the auxiliary systems (such as lights, A/C, etc.).

If you don't know how to do these tasks, then it would be best to take the car to a shop with a tech experienced in basic automotive electrical troubleshooting. These cars are particularly easy and accessible to do this work on and shouldn't present any big challenge to a competent tech. And the components in these cars are pretty well designed and up to the tasks.
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Old 02-24-2015, 08:23 AM
26,163 posts, read 14,457,966 times
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Originally Posted by Mike from back east
No. I'll move it to automotive for the OP.
Danke Mike

I hope we can help him!!
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