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Old 10-02-2015, 09:22 AM
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maxhifi maxhifi is offline
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Troubleshooting Truck electrical

Monday night I went to start the truck, and was greeted with a run down battery. Not enough juice left to crank it fast enough to start.

Checked out electrical system, and figured out there was no output from alternator. Bought a new alternator, but before I changed out the whole thing I decided to try just the voltage reg. And brushes from the rebuilt alternator.

Sure enough it works now, battery charges, back to normal

But: charge voltage is 13 at idle and 13.5 with engine revved up high. It's within spec but seems to me kind of low, and I am at a loss as to why. I would much prefer to see 13.8 - 14.5 with engine revving.

I am thinking for next steps: check battery terminal of alternator with scope to verify if I have any bad rectifiers

Check charge current at idle to verify if I have any parasitic loads

Unfortunately regulators for this alternator are pricey so I can't easily swap in a new one just for the sake of testing.

Truck is an 86 Toyota pickup, with 2.4 Diesel engine.
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Old 10-02-2015, 11:02 AM
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Why not just install the rebuilt alternator you already bought?

Depending on the year the charging voltage may be controlled by the PCM.

It may be keeping the voltage low so the amperage doesn't get too high pushing against a low battery..
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Old 10-02-2015, 11:14 AM
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Originally Posted by Eric H View Post
Why not just install the rebuilt alternator you already bought?

Depending on the year the charging voltage may be controlled by the PCM.

It may be keeping the voltage low so the amperage doesn't get too high pushing against a low battery..
I think will do just that. On the way to work today the "charge" light came on a few times when I was stuck in traffic. I had to rev it up to get it to extinguish. The reason I installed just the regulator, is the alternator has an oil lubricated vacuum pump mounted on the back of it for the brakes. I didn't have enough time that evening to do the whole job, so just at first tried the regulator to try and get it going.

The truck is very simple, there's no computer or external electronics, the regulator is just a little steel can which Toyota refers to as an "IC Regulator" and is attached to the brush holder under a little metal cover.
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Old 10-02-2015, 08:46 PM
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Thanks Eric - new alternator gives 14.1 V at idle and 14.4 revved up... All seems normal now. It seems odd to me that the olds alternator and old regulator both went bad at once, but it's nice to have the truck back to normal.
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Old 10-03-2015, 09:58 AM
dieseljeep dieseljeep is offline
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Originally Posted by maxhifi View Post
Thanks Eric - new alternator gives 14.1 V at idle and 14.4 revved up... All seems normal now. It seems odd to me that the olds alternator and old regulator both went bad at once, but it's nice to have the truck back to normal.
Hang on to that baby for dear life.
I don't know why Toyota doesn't build a truck with a small diesel. They built one of the best.
If you don't believe it, talk to the people in Cuba.
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Old 10-03-2015, 10:39 AM
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Hang on to that baby for dear life.
I don't know why Toyota doesn't build a truck with a small diesel. They built one of the best.
If you don't believe it, talk to the people in Cuba.

I know what you're saying! It was actually a trip to Cuba that had me looking for a Toyota diesel in the first place. I will keep it going as long as possible, this is for sure, there's no real modern equivalent.
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Old 10-03-2015, 12:05 PM
dieseljeep dieseljeep is offline
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I know what you're saying! It was actually a trip to Cuba that had me looking for a Toyota diesel in the first place. I will keep it going as long as possible, this is for sure, there's no real modern equivalent.
My late diesel Jeep Liberty, RIP, had the 2.8L VM Motori, Italian built diesel. I had the first year production and it had a few growing pains. The transmission was technically undersized for the amount of torque of a diesel, VS, a gasoline engine. Also, the driveline components, U-joints, ETC.
The next year, all of those issues were corrected, but the sales wouldn't support, continuing the sales in the US.
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Old 10-03-2015, 02:39 PM
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Quote:
Originally Posted by maxhifi View Post
Thanks Eric - new alternator gives 14.1 V at idle and 14.4 revved up... All seems normal now. It seems odd to me that the olds alternator and old regulator both went bad at once, but it's nice to have the truck back to normal.
All the Fords me and the entire family had years ago, whenever you had
charging system problems, you ended up changing all three to finally get a
few years peace out of the system..... Battery, Alt, and regulator. You couldn't
use yer brain, or a meter to fix it, you just had to replace it all, or you would
be replacing each part over and over......
1972 - 86 If the battery was 2 year old or less it usually was ok.

Our Honda's are much better, and also odd in that we have 6 honda's in the
family. 1986 - 1996, Each Alt. went at around 170K miles, then with 300K to
420K on those cars presently, the second Alt. in each car, A Honda Factory
rebuild has not had any troubles....

.
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Last edited by Username1; 10-03-2015 at 02:46 PM.
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Old 11-04-2015, 08:12 PM
tvdude1 tvdude1 is offline
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I have owned my repair shop for 36 years now and I only use BOSCH alternators and starter even in us cars no Auto Zone junk . Bosch top quality no come backs.
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Old 11-04-2015, 08:46 PM
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With the Toyota it was a matter of what was possible to find - last year the 2.4l diesel was sold was 1986, and with how old cars rust around here the demand for parts has got to be nearly nil. It's still working so the new alternator definitely did the trick!
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Old 11-05-2015, 08:41 AM
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Originally Posted by tvdude1 View Post
I have owned my repair shop for 36 years now
and I only use BOSCH alternators and starter even in us cars no Auto Zone
junk . Bosch top quality no come backs.
Funny, My brother use to get AZ stuff cause it was guaranteed forever, but
he use to have to replace it every year or two. I asked him, so where is
the bargain in that ? AZ is a mindset kinda place. The labor to keep replacing
cheap guaranteed forever junk is too expensive....

.
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Old 11-05-2015, 11:05 AM
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Quote:
Originally Posted by Username1 View Post
Funny, My brother use to get AZ stuff cause it was guaranteed forever, but
he use to have to replace it every year or two. I asked him, so where is
the bargain in that ? AZ is a mindset kinda place. The labor to keep replacing
cheap guaranteed forever junk is too expensive....

.
Not to mention the hassle of being broke down somewhere,
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  #13  
Old 11-05-2015, 11:37 AM
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Yes ~ He was one of only one person I know who has ever had a battery explode
in his car from overcharging..... His '86 T-bird, the car he had during his AZ years,
whenever the alt. light would come on, once or twice a year, he said "I got 20 seconds
to close all the windows, and get parked, then the car's dead in the water..... I told him
after watching it for a few years, "Go get all new stuff from the dealer and fix it once,
and be done with it" I am pretty much a fan of OE parts, our '79 Mercury
(Colony Park ??) LTD wagon had a original new Ford battery from the factory
last 10 years...... Amazing ! !

.
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