GorgeRunner

Yesterday the brake and charge lights came on in my 1990 pickup. It is a standard pickup, 22RE, 4 speed manual transmission.
At first, I figured the alternator was bad, but I checked it with a meter and it is charging at about 14.5v. I pulled the battery cable with the engine running and it doesn't die so I figure the alternator is good. Cleaned all the ground contacts, checked the wiring and fuses, E-brake switch, everything looks fine.
I've searched the internet about this problem and it seems pretty common. It's the alternator most of the time, but after that, the solutions are a bit fuzzy.
I've read about a relay behind the glove box? Older Toyotas had this relay, what about a 1990? Would that be a logical assumption with the symptoms I have that the relay is bad? If it is a relay, will I harm the alternator or battery by driving with the lights on? The Toyota dealer is about 25 freeway miles from here.
I'll keep researching the problem, but any advice from the gang here at Yotatech would be greatly appreciated.

scope103

Sufficient brake fluid? That shouldn't have anything to do with the ALT light, but solve one problem at a time.

jerry507

You don't happen to have LED replacement lights in your combo meter do you???

GorgeRunner

Brakes/brake fluid is fine, relatively new master cylinder. No LED replacement bulbs.
Thanks for your input, I'm open to any and all suggestions. Even the mechanics at the local Toyota dealership may not be old enough to understand the problems of a twenty three year old truck. This will be a problem a Toyota enthusiast will have to figure out.

jerry507

Ok, second question. When you actually engage your ebrake, does the light get brighter or stay the same? You can also test this by turning on your turn signal and seeing if the lights pulse in brightness. You can also try shorting the brake fluid level sensor as well.

It's hard to do in the daytime though.

wyoming9

iTrader: (1)

Just where did you measure your voltage?? this would be with a full electrical load.

***Know that these lights will also light up in a over charge condition if the voltage regulator is allowing to much output!!!!

:wabbit2:

The lights are still on all the time. they never go out now??

Have you checked the belt tension??

All the fuses involved with the charging system?? You did check these with a meter ?/

I have seen the sockets in the fuse block corroded and loose enough not to make contact.

ilovelivinginthecity

RAD4Runner

Would not turn over as starter motor not turning, of would not fire? If starter not turning, ignition coil has no relation to that.

Relay under passenger side, behind glove box? That's the Circuit Opening Relay. Nothing to do with brake nor alternator

Might need to replace your shop =D

Low beam filament in bulb busted. Check resistance between each terminal of bulb on passenger side. Compare with readings on driver's side.

Headlight schematic here:

RAD4Runner

Happy New year, folks!

Would help if you mentioned what engine your truck has and IF you could post its schematic for those who want to help but have different year-model. Anyway, conceptS should be similar. 22RE Charging schematic is below.
. Not very precise hut helps with troubleshooting.

Yes, looks like your alt is charging alright. You monitored battery voltages while running/revving up? Should stay between 13.5 and 14.5Volts if internal regulator of alt is OK. Alt has "L" output (yellow wire on 22RE). This is only either low (under/over charging) or 12V (charging properly). It connects to charge fuse. When alt is putting out voltage in proper range (somewhere between 13.5 and 14.5V) that output is 12V. If below 13.5 (undercharging) or IF above a certain voltage (around 14.5 / overcharging), "L" output goes low (maybe around 2V or nothing). This will provide "negative" voltage to charge and brake lights and cause them to turn on. With engine running, check voltage at either side of "Charge" fuse. Should be around 12V. If not, suspect regulator.

Not aware of a relay behind glove box that affects charging. There's a ircuit Opening Relay behind the glove box. Explanation in my build thread.

GorgeRunner

Thanks for all the input. What seemed to be a simple problem at first(bad alternator) has become quite the electrical dilemma
The voltage was measured across the battery terminals. 12.6v with engine off after a night of temps in the mid 20's. 14.7-14.9v with engine running, no lower than 14v with lights, heater fan and radio on.
Lights on all the time.
Yes, it's OK.
Yes, I checked all the truck's fuses with an ohmeter and cleaned the terminals with a wire brush, including the 7.5A charge fuse under the hood.
Sorry, it's a 22RE, 4 speed manual transmission, basic pickup truck. I've edited the original post to include this.
Some Toyotas have a Charge Lamp Relay behind the passenger kick panel/glove compartment. If the charge/e-brake lights are on but go off when you slam the passenger door or go over a bump, this relay would be suspect. I don't know if my year truck has this relay or not. If it does, it would be the prime suspect for my problem. I'll ask the local Toyota dealer parts department if they have this relay listed for my year truck.
After reading what's been posted here, what I'm going to look at now are:
I'll take another measurement tomorrow, as I recall, all the voltage readings at the battery with the engine running have been over 14.5v. Overcharging is something I have not considered, but if that's what the meter says...
I am going to check this voltage as well, I have not checked it yet. Can you do this reading with the 7.5A fuse removed(you are talking about the charge fuse in the engine compartment?).
Thanks again for all the input. I've been working on cars my whole life and I work as an electronics technician, but I still hate automotive electrical problems, especially behind the dashboard.

jerry507

14.5V would be an acceptable voltage on the battery. Definitely check the fuses though.

There actually isn't a shared path between these two lights according to the FSM, aside from the hot side supplying power for the light. The alternators L terminal grounds out when the regulator stops working, which completes the circuit for the light. The ebrake circuit works the same way, with the ebrake switching ground.

Checking these voltages at the combo meter would be the best option, but you might not want to rip your dash out

RAD4Runner

Agree.

Actually where it connects to combination meter (my notes in green in lower-left of schematic), it will also ground brake light. That's why fault with alt also causes brake light to come on.


YOu can actually extract the pin from the very first connector as it comes from ALT, so when you re-connect the connector everything works BUT "L" is not connected to charge fuse. This may turn off brake and charge light because now they do not see low volt/ground.

Run engine and check voltage at this "L" pin. If still low, possible that it's really sensing poor regulation, OR simply disconnected internally from ALT circuit.

jerry507

At least on the schematic I have, the charge light is powered by the IGN fuse through pin B3. It leaves the combo meter on B4 to the L terminal. There isn't a shared path in the meter itself. Is that schematic for a 1st or 2nd gen pickup? It also looks significantly different from mine.

GorgeRunner

Here are the wiring diagrams I am working with:





And the fuse and relay locations:



I am going to take more detailed voltage readings today, I am wondering what overcharge voltage will trigger the charge light; is it 14.8v, 14.9v, 15v? The alternator is definitely charging, I wonder about the regulator.
I think this is where I am going to focus my troubleshooting, I starting to suspect the regulator is bad and the alternator is overcharging.
No, I don't want to go behind the dash if I can help it. I have to work outside and it is cold here. I don't think it is a dashboard wiring problem, I still suspect a bad alternator/regulator, blown fuse or maybe a bad ground or wire in the engine compartment would be my next guess. I take pretty good care of my truck and I just cleaned all the battery connections and grounds before winter.
The alternator that is in the truck is a remanufactured unit that is nearly six years old so I would think it's in the range of where you might expect it to fail. Before I rip the dash out, I'd bite the bullet, buy another alternator and hope that takes care of it. I don't want to run the truck with the warning lights on either, if they burn out, then I will have to remove the dashboard.
All my previous alternator/generator failures have been where the unit is not charging, easy to diagnose. This situation is a little different.

jerry507

Direct from my FSM:

G1(B), G2 (A) GENERATOR (ALTERNATOR)
(A) 3–GROUND : APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION
(B) 1–GROUND : 13.9–15.1 VOLTS WITH ENGINE RUNNING AT 2000 RPM AND 25°C (77°F)
13.5–14.3 VOLTS WITH ENGINE RUNNING AT 2000 RPM AND 115°C (239°F)
C12 CHARGE WARNING LIGHT [COMB. METER]
3–GROUND : APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION

I'll be honest, I don't believe there is any overcharging light. The way an automotive alternator regulator works makes it pretty hard for it to fail. The regulator can't stop working and the alternator keeps generating. It has to very specifically go out of spec. This would be very obvious as a change in the alternator output voltage.

GorgeRunner

I'm not sure exactly how the idiot light works, but since the only component between the charge warning light and the alternator is the 7.5A Charge fuse, isn't circuitry in the regulator is what causes the light to come on in when the alternator output is out of range? If the fuse and wiring are good, even if the alternator is charging, might there be a problem with the part of the regulator that is sending current to the warning light?
I checked the voltages, here's what I have:
Battery, cold after a night of freezing temps: 12.34V, after running at idle 10 minutes: 13.3v
Charging:
Immediately after starting, fast idle, cold: 14.95v
Warm engine, normal idle speed: 14.7v
Warm engine, idle, lights, heater fan, radio, turn signal on: 14.45v
Voltage at 7.5A Charge fuse: .179-.182v

Voltage at 7.5A Charge fuse: .179-.182v If that's the case then I have to assume the regulator is bad

RAD4Runner

Yep, 14.95V and 14.7V seem too high. That probably triggers "L" output to go low. (you gotta research and verify that).
BTW, I had similar but opposite problem after washing my engine. Charging voltage going as low as 13.25V, so "L" output also low

Really looks like the control circuit is sensing that over-voltage (14.95V or 14.7V), OR "a problem with the part of the regulator that is sending current to the warning light?"

Either way, OK to keep running as long as you monitor charging voltage, but need to have alt looked at.

RAD4Runner

Thanks for the schematic, Jerry507.
Did you check where "From Combination Meter" wire encircled in blue and yellow below goes? It connects to negative side of brake light on my 2RE.

jerry507

Since the latest culling of service manuals from the internet, I can't easily link. I'll have to throw up some dropbox links tonight so we can visually see where we're going. On my schematics, there isn't a third wire in the combo meter. Ignition comes in connector B, pin 3 and the cathode side of the diode (the wall) leaves connect B pin 4.

After digging around a bit more, I apparently have a wiring manual that is different from the service manuals. I'll have to be a lot more careful about this from now on. I'd stick with just troubleshooting the alternator now, because between the 93PU manual, 95 runner service, and 95 runner wiring, there are pretty significant differences between all three manuals.

GorgeRunner

The combination of the consistent high voltage at the battery and the really low voltage at the 7.5A Charge fuse, in addition to the fact the alternator is a nearly six year old remanufactured unit were enough to make me spring for a new remanufactured alternator from NAPA($73-10% AAA discount). I know a Toyota Denso would be better, but for a truck this old that doesn't see much offroading, it's tough to justify the cost.
I'll put it in tomorrow and hope for the best.
Is the "Combination Meter" a group of dashboard gauges? My truck only has idiot lights.