alternator problems 100 series (1 Viewer)

[toyotanorthny]

1999 with 197k miles.
Hey guys, I need an opinion on a problem that I am confronting with my alternator. Several weeks ago I noticed that average amp rating for my battery was 13.2 and under load it would drop down to 12.4.
I was thinking my original from 1999 alternator was on the way out, so I took it to mechanic. he said it was alternator dying. I ordered 80amp Denso rebuilt unit and had it installed. Now same scenario that it would yield 13.2 and under load it would drop to 12.3 or so.
Had denso alternator new for only 2 days with average 13.3 until today when I left house and 5 mins later instrument panel stop working, horn was low, windows slow, etc. from 13.4 it drop to 8.3 in matter of minutes until car completely stopped after only driving 6 miles.
I was stranded. Had to get towed. Nearby mechanic stated I had a bad alternator. Bought generic brand as I had no choice. Mechanic installed and i got only 11.3 out of second new alternator. He was baffled.
Mechanic checked fuses and replaced one near firewall on right side. Now battery shows 13.3. Does not go above that. Now I have lost confidence in driving far as I don't know if this thing was resolved properly. Any ideas ? any input and feedback is greatly appreciated.

 

[suprarx7nut]

Sounds silly, but have you or mechanics checked the cables to the battery?

 

[toyotanorthny]

yes they are all good

 

[94SRUNNER]

How about all your grounds?

 

[toyotanorthny]

good idea.....will check tomorrow

 

[94SRUNNER]

Worth going through all of them to check for corrosion and cleaning up with a wire brush and or sandpaper.

 

[toyotanorthny]

great input. so we can say that alternator should be at 14.1 to 14.6 and under load no less than 13.6 ?

 

[94SRUNNER]

great input. so we can say that alternator should be at 14.1 to 14.6 and under load no less than 13.6 ?

Ideally yes. However, mine runs lower and always have. I typically see 13.2-13.8v and have had a storied history with alternators and my LX. The alternators have been test at a local independent alternator shop and various auto parts stores and they have tested within specification every time, both in and out of the vehicle. I have also gone through all the engine bay ground connections and cleaned them up and replaced the fusible link. The connection at the alternator is also in good condition. I need to compare the voltage at the battery versus what the ScanGauge displays.

Alternator Replacement - A Saga

I have had some poor luck with alternators. By my count I am on my fifth alternator. A bit of history... First off, my LX is basically stock. Nothing that I can figure would cause an alternator to fail prematurely. No leaking coolant or oil from the engine that would cause failure. The area...

forum.ih8mud.com

 

[toyotanorthny]

Ideally yes. However, mine runs lower and always have. I typically see 13.2-13.8v and have had a storied history with alternators and my LX. The alternators have been test at a local independent alternator shop and various auto parts stores and they have tested within specification every time, both in and out of the vehicle. I have also gone through all the engine bay ground connections and cleaned them up and replaced the fusible link. The connection at the alternator is also in good condition. I need to compare the voltage at the battery versus what the ScanGauge displays.

Alternator Replacement - A Saga

I have had some poor luck with alternators. By my count I am on my fifth alternator. A bit of history... First off, my LX is basically stock. Nothing that I can figure would cause an alternator to fail prematurely. No leaking coolant or oil from the engine that would cause failure. The area...

forum.ih8mud.com

thanks for sharing original post. Lots of talk about denso's reliability of rebuilt units. So what is the best choice in your opinion for an aftermarket alternator ?
what finally ended up in your rig?

 

[AlpineAccess]

thanks for sharing original post. Lots of talk about denso's reliability of rebuilt units. So what is the best choice in your opinion for an aftermarket alternator ?
what finally ended up in your rig?

The denso is still likely the best option, if trouble shooting it doesn't work you should be able to return for a replacement.

Howis your battery's condition?

 

[94SRUNNER]

thanks for sharing original post. Lots of talk about denso's reliability of rebuilt units. So what is the best choice in your opinion for an aftermarket alternator ?
what finally ended up in your rig?

Well, out of necessity I put in a Denso reman unit. I have an OEM unit on the shelf which I am going to do a complete tear down and rebuild on, and install it at some point.

 

[highkick05]

Worth going through all of them to check for corrosion and cleaning up with a wire brush and or sandpaper.

cleaning the neg and positive terminals and connectors got me an additional .1 Volt which is a lot considering. might get .2 on some ppls

def worth doing

 

[94SRUNNER]

cleaning the neg and positive terminals and connectors got me an additional .1 Volt which is a lot considering. might get .2 on some ppls

def worth doing

Yes. Keeping the battery terminals and connectors clean and dressed with dielectric grease is good practice.

 

[gil12]

I'd replace the battery and then check things again. A poorly charged battery (from a bad alternator) will quickly crap out. They don't like being undercharged for very long. That can produce confusing readings from the new alternator, I suspect.

 

[highkick05]

I'd replace the battery and then check things again. A poorly charged battery (from a bad alternator) will quickly crap out. They don't like being undercharged for very long. That can produce confusing readings from the new alternator, I suspect.

Sealed calcium batteries don't get charged correctly by these alternators. Reason why I'm going to put a solar panel on my roof and get a Projecta solar charge controller to hit the starter battery with 14.9V while it sits out front - the correct voltage calcium batteries should be getting.

 

[white_lx]

Also check the Alt-S fuse & circuit. The fuse is housed in the little housing (fusible link block) mounted to the positive battery terminal. The Alt-S circuit provides feedback to the alternator and regulates the alternator output voltage. Is the battery light coming on? Also check the fusible link block for corrosion as it will result in a non-charging battery even though the output of the alternator is OK. You can do this by measuring the voltage before and after the fuse block under load.

See this video at 2m:00s for an excellent description of Toyota's charging system:

 

[nckwltn]

Do you have an FR-IG fuse? In my '03, I was having similar issues with my voltage from the alternator. I found that the FR-IG circuit wasn't getting triggered by the relay. Not sure if the '99 is different, but I'm understanding the FR-IG circuit to tell the alternator that the car is on and that it should start kicking out voltage. the ALT-S circuit tells the alternator how much voltage it should output.

During all of this, my battery light wasn't coming on. I also traced that back to the FR-IG fuse/circuit.

I've found that jostling the fuse panel under the hood can kick the relay into gear, and then I don't have any issues the whole day. It's only first thing in the morning that I end up having issues.

I have not yet replaced the relay, but it is on my list to take care of.

 

[94SRUNNER]

Do you have an FR-IG fuse? In my '03, I was having similar issues with my voltage from the alternator. I found that the FR-IG circuit wasn't getting triggered by the relay. Not sure if the '99 is different, but I'm understanding the FR-IG circuit to tell the alternator that the car is on and that it should start kicking out voltage. the ALT-S circuit tells the alternator how much voltage it should output.

During all of this, my battery light wasn't coming on. I also traced that back to the FR-IG fuse/circuit.

I've found that jostling the fuse panel under the hood can kick the relay into gear, and then I don't have any issues the whole day. It's only first thing in the morning that I end up having issues.

I have not yet replaced the relay, but it is on my list to take care of.

Where is the FR-IG fuse? Main fuse box under the hood?

 

[nckwltn]

Where is the FR-IG fuse? Main fuse box under the hood?

Correct.... but that is on my '03 LX470

 

[94SRUNNER]

Correct.... but that is on my '03 LX470

I'll dig around when I take my lunch break.