07-07-2020, 04:09 PM
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#1
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Decrease In Engine Power Due To Electrical Load?
Looking for some insight.
I noticed the other day that when i lower the windows while driving, there's a noticeable decrease in engine power. Even if the windows are all the way down and I press the window buttons and hold them down, I get the same effect. It kind of caught me off guard. It's similar to the effect when I turn on the AC. The engine just seems more tasked. The alternator is original. (240k mi). All windows including the moon roof seem to close pretty slowly as well.
Any thoughts?
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'98 4Run SR5 v6 4x4-Orig Owner
Manual Transmission
Bilstein 5100 (front/rear)
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'99 Tall Springs (front)
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07-07-2020, 04:49 PM
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#2
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Sub'd to follow along. I've noticed the same thing occur on the highway when my A/C compressor kicks in. Haven't wanted to mess with it because the A/C currently works. Interested to see if anyone has ideas. To my knowledge my alternator is also original (223k).
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07-07-2020, 05:05 PM
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#3
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Greyhome, AC will definetely cause a decrease in engine performance. The AC compressor requires a few horsepower (say, 2-5), which is easily enough to feel while cruising down the road (when you are using say, 20-40 to cruise at a constant speed).
I'm surprised you can feel a change with the windows. What I can tell you though, is that DC motors draw MORE current when they are stopped, like at the end of the window motor travel. That's actually how the auto-down feature works on the front windows... (it senses excess current draw and turns off, the auto-up has some pinch detection and limit switches for safety instead)
-Charlie
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07-07-2020, 10:47 PM
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#4
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Quote:
Originally Posted by psea17
Looking for some insight.
I noticed the other day that when i lower the windows while driving, there's a noticeable decrease in engine power. Even if the windows are all the way down and I press the window buttons and hold them down, I get the same effect. It kind of caught me off guard. It's similar to the effect when I turn on the AC. The engine just seems more tasked. The alternator is original. (240k mi). All windows including the moon roof seem to close pretty slowly as well.
Any thoughts?
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Interesting. Curious as well
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07-07-2020, 11:22 PM
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#5
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Brand new battery and oversized alternator. I feel the same lug on the engine when parked or stopped. When the battery is low, it's more pronounced.
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07-08-2020, 09:09 AM
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#6
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Our factory Alts are 960w. I can’t see that drawing more than 2hp fully fielded. The AC requires more HP........
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07-08-2020, 09:28 AM
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#7
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Quote:
Originally Posted by psea17
Looking for some insight.
I noticed the other day that when i lower the windows while driving, there's a noticeable decrease in engine power. Even if the windows are all the way down and I press the window buttons and hold them down, I get the same effect. It kind of caught me off guard. It's similar to the effect when I turn on the AC. The engine just seems more tasked. The alternator is original. (240k mi). All windows including the moon roof seem to close pretty slowly as well.
Any thoughts?
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Have you ever replaced the alternator brushes? If not, find some - probably will need to order since nobody carries them. Mine wore out at about 220k. I didn't experience your symptom, it just failed. I imagine if they're making poor contact it could be not charging well, taxing the alternator.
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07-08-2020, 03:26 PM
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#8
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Just to be clear. I'm not talking about the reduction in HP when the AC is engaged. I was just using that situation to describe the situation.
Since starting this thread, I just completed the Big Three+ Rewire. (alternator to battery+, engine block (oem location=beneath oil filter) to battery-, battery- to body (oem location), battery- to frame). The battery to frame was added because I'm running 2ga to an Anderson Plug I located at the rear trailer hitch area. The plug is grounded to the frame. The plug will have two uses: a) charge my trailer's batteries (a BlueSea ACR was installed at the truck's battery to disconnect when the truck isn't running; prevents the trailer from draining the truck's battery) and b) should I decide to use my winch, which will be mounted on a tray that fits into the trailer hitch, it will have all the juice it needs.
My alternator increased output at idle from 13.98v to 14.25v. Very happy. Will report on the window power draw a little later. I have not changed the alternator's brushes. But, I would guess based on the alternator's output, the brushes should be fine.
Appreciate any other insights.
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'98 4Run SR5 v6 4x4-Orig Owner
Manual Transmission
Bilstein 5100 (front/rear)
OME 890 Springs (rear)
'99 Tall Springs (front)
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07-08-2020, 04:35 PM
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#9
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Quote:
Originally Posted by psea17
Just to be clear. I'm not talking about the reduction in HP when the AC is engaged. I was just using that situation to describe the situation.
Since starting this thread, I just completed the Big Three+ Rewire. (alternator to battery+, engine block (oem location=beneath oil filter) to battery-, battery- to body (oem location), battery- to frame). The battery to frame was added because I'm running 2ga to an Anderson Plug I located at the rear trailer hitch area. The plug is grounded to the frame. The plug will have two uses: a) charge my trailer's batteries (a BlueSea ACR was installed at the truck's battery to disconnect when the truck isn't running; prevents the trailer from draining the truck's battery) and b) should I decide to use my winch, which will be mounted on a tray that fits into the trailer hitch, it will have all the juice it needs.
My alternator increased output at idle from 13.98v to 14.25v. Very happy. Will report on the window power draw a little later. I have not changed the alternator's brushes. But, I would guess based on the alternator's output, the brushes should be fine.
Appreciate any other insights.
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I'll assure you that, if those brushes are original, they're about finished. Easy enough to check. May not be causing your problem, but a great preventive measure.
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07-08-2020, 06:18 PM
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#10
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Glad to see you upgraded the grounds, its a closed loop system so adding more power doesn't help if the grounds are at their capacity. I did a battery to frame to engine block ground on my tacoma and it helped and definitely made it start quicker
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07-08-2020, 08:47 PM
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#11
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do you know what the p/n is for the brushes and where I can find them? much appreciated.
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'98 4Run SR5 v6 4x4-Orig Owner
Manual Transmission
Bilstein 5100 (front/rear)
OME 890 Springs (rear)
'99 Tall Springs (front)
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07-09-2020, 01:16 AM
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#12
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Quote:
Originally Posted by psea17
My alternator increased output at idle from 13.98v to 14.25v.
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This is with the same OEM alternator? Also, alt V. output is temperature dependent: Higher volts at lower temperature.
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07-09-2020, 01:24 AM
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#13
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Quote:
Originally Posted by pluton
This is with the same OEM alternator? Also, alt V. output is temperature dependent: Higher volts at lower temperature.
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yes, same oem alternator.
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'98 4Run SR5 v6 4x4-Orig Owner
Manual Transmission
Bilstein 5100 (front/rear)
OME 890 Springs (rear)
'99 Tall Springs (front)
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07-09-2020, 05:08 AM
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#14
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Quote:
Originally Posted by psea17
do you know what the p/n is for the brushes and where I can find them? much appreciated.
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27370-75060, I believe. Here's one place to check:
Toyota 4Runner Alternator Brush - Guaranteed Genuine Toyota Parts
There are videos on replacement, but it's a 5-minute job when you have the alternator out.
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07-09-2020, 11:10 AM
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#15
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Quote:
Originally Posted by psea17
do you know what the p/n is for the brushes and where I can find them? much appreciated.
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You need to determine if you have the 70a or 80a unit. They are different part numbers.
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