Alternator output question - '98 4Runner
#1
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Thread Starter
Alternator output question - '98 4Runner
My friend is visiting from out of state and had a strange thing happen today about an hour from my house. As he was driving, the interior fan suddenly stopped, the windows no longer operated, and the temp gauge, tach and speedo all went dead. He drove it to a nearby Advance Auto and had them check the alternator output - it was around 11.5v. Assuming the alternator had suddenly quit, he purchased the only unit on the shelf and I headed out with a bucket of tools.
We got the 'new' alternator installed without issue, fired the truck up, and saw no change. Thinking one or more of the connections may be dirty, corroded, etc., we did the entire job again only to have the same result. The guy from Advance Auto tested the old alternator and found it was fine when checked on the bench....
The truck is a 1998 SR5, 4WD, 5-speed with 250,000 miles. He's owned the truck since new and has not had any electrical issues to date.
Any thoughts on what may be causing the undercharging? I assume the alternator is looking for a signal voltage to produce a charge.
Andreas
We got the 'new' alternator installed without issue, fired the truck up, and saw no change. Thinking one or more of the connections may be dirty, corroded, etc., we did the entire job again only to have the same result. The guy from Advance Auto tested the old alternator and found it was fine when checked on the bench....
The truck is a 1998 SR5, 4WD, 5-speed with 250,000 miles. He's owned the truck since new and has not had any electrical issues to date.
Any thoughts on what may be causing the undercharging? I assume the alternator is looking for a signal voltage to produce a charge.
Andreas
Last edited by aowRS; 10-04-2015 at 06:54 PM.
#2
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At any time was the battery checked ??Battery terminals clean and tight.
Were you checking the output with your own meter ??Clueless counter person ??
I can only guess the charge light was on the whole time.
Poor connection because of corrosion on the alternator plug
open fuse or circuit in the charging system
One of those things you need to check one step at a time
Were you checking the output with your own meter ??Clueless counter person ??
I can only guess the charge light was on the whole time.
Poor connection because of corrosion on the alternator plug
open fuse or circuit in the charging system
One of those things you need to check one step at a time
#3
Contributing Member
Thread Starter
At any time was the battery checked ??Battery terminals clean and tight.
Were you checking the output with your own meter ??Clueless counter person ??
I can only guess the charge light was on the whole time.
Poor connection because of corrosion on the alternator plug
open fuse or circuit in the charging system
One of those things you need to check one step at a time
Were you checking the output with your own meter ??Clueless counter person ??
I can only guess the charge light was on the whole time.
Poor connection because of corrosion on the alternator plug
open fuse or circuit in the charging system
One of those things you need to check one step at a time
- Battery checked fine and terminals clean & tight.
- Output checked by Advance Auto guy.
- No charge light illuminated.
- Alternator plug & three prongs looked factory new (grease still on red o-ring)
Andreas
Last edited by aowRS; 10-04-2015 at 11:51 PM.
#4
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It doesn't seem like the symptoms as described would caused by a poorly charging alt/ bad battery, would they?
#5
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Andreas
#6
What does this mean?
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#8
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Signal from voltage regulator?
#9
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Thread Starter
A bit more info: we found that a section of the positive cable was severely hosed (pic below), so we installed a new cable. After doing so, the alternator was showing ~12.3v charging vs. the 11.something we saw last night. So presumably the new & intact cable allowed an additional volt worth of charging...
We checked continuity on all three wires of the alternator harness - they're good (that includes the signal wire). The actual charge wire checks good from the lug on the alternator to where it terminates at the fuse block.
So, the windows are still dead, the tach, temp gauge, and speedo are dead and the alternator still does not push out enough juice.
Thoughts?
Andreas
We checked continuity on all three wires of the alternator harness - they're good (that includes the signal wire). The actual charge wire checks good from the lug on the alternator to where it terminates at the fuse block.
So, the windows are still dead, the tach, temp gauge, and speedo are dead and the alternator still does not push out enough juice.
Thoughts?
Andreas
Last edited by aowRS; 10-05-2015 at 07:57 PM.
#10
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You have gone through and checked all the fuses with a meter ??
Cleaned and inspected all the major grounds where they attach to the vehicle.
The white wire coming off the B terminal of the alternator to the fuse block??
Is it possible to check your alternator output at the B terminal of the alternator
10 Amp gauge fuse Open??
windows pull power from there as well as the alternator !!!
Cleaned and inspected all the major grounds where they attach to the vehicle.
The white wire coming off the B terminal of the alternator to the fuse block??
Is it possible to check your alternator output at the B terminal of the alternator
10 Amp gauge fuse Open??
windows pull power from there as well as the alternator !!!
#11
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Thread Starter
All fuses checked with meter.
Cleaned & inspected every ground we've been able to I.D.
White wire is one of three in alternator plug - it checks out.
Andreas
Cleaned & inspected every ground we've been able to I.D.
White wire is one of three in alternator plug - it checks out.
Andreas
#13
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Thread Starter
Yes, that wire is good.
I'm sure my buddy would take you up on that offer - he's somewhat stranded in MD until we get to the bottom of this.
Andreas
I'm sure my buddy would take you up on that offer - he's somewhat stranded in MD until we get to the bottom of this.
Andreas
#14
Registered User
Was that positive cable fried/overheated?
Really sounds like some other sort of problem, not the alternator.
Probably time to start pondering a wiring diagram, and working backward from some component that isn't working, junction by junction, to the fuse block. See where the 12V+ stops.
Really sounds like some other sort of problem, not the alternator.
Probably time to start pondering a wiring diagram, and working backward from some component that isn't working, junction by junction, to the fuse block. See where the 12V+ stops.
#15
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Thread Starter
Was that positive cable fried/overheated?
Really sounds like some other sort of problem, not the alternator.
Probably time to start pondering a wiring diagram, and working backward from some component that isn't working, junction by junction, to the fuse block. See where the 12V+ stops.
Really sounds like some other sort of problem, not the alternator.
Probably time to start pondering a wiring diagram, and working backward from some component that isn't working, junction by junction, to the fuse block. See where the 12V+ stops.
I agree that the issue is probably not with the alternator. My friend is in somewhat of a time crunch so he's currently at the local dealer to see if they can somehow magically pinpoint the problem.
Andreas
#16
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Thread Starter
Problem solved. A tech at the local Toyota dealer found a 10a fuse that was blown. Supposedly this fuse controlled all of the items that were out of commission. Odd because we checked each fuse...
When the tech reversed the truck to pull it out of the bay, the fuse popped again. So after some more trouble shooting, he found a short somewhere in the trailer wiring.
My buddy is on his way back home now. What a fiasco.
Andreas
When the tech reversed the truck to pull it out of the bay, the fuse popped again. So after some more trouble shooting, he found a short somewhere in the trailer wiring.
My buddy is on his way back home now. What a fiasco.
Andreas
#17
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That makes a lot more sense! Glad the short was found, it's so aggravating when a fuse looks good when it's not. Also glad you posted up too, been wondering what the final verdict would be. Thank goodness it was simpler than it could have been!
#19
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#20
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