More 4Runner fun. Now it's the dash lights...

Factual Questions
1

Hi. It’s me again with my wonky 1990 4Runner.

The dashboard lights are the new annoyance. They used to flicker every now and then but for the past couple months seem to do it much more frequently. I’ve been trying to find rhyme or reason for it but am having a hard time coming up with anything that may be cause and effect.

The lights that flash are the Brake(!), battery, and the A/T Oil Temp. They all flash together, every time. My manual brake are released, the voltmeter on the dash is happy, and the truck seems to be shifting normally.

The only thing that seems like a common cause is that the truck has to warmed-up a bit before they start to flash and flicker, they never flicker when the engine is cold. Sometimes they seem to flash with the bumps of the road but also, the other day, they were flickering while sitting motionless at a traffic light.

My thought has always been that’s it’s a simple but annoying short in the dashboard and that it’s all bogus. If that’s the case, though, the “the car must be warm” part doesn’t seem to make sense.

My more recent thought is that it’s a single valid problem but it’s energizing too many indicator lights by mistake.

In an attempt to diagnose, thinking it may the A/T oil temp, I made great effort to keep splashing through ice-cold puddles on a recent cold rainy day. The theory was that I’d keep the transmission soaked and cold. It might have worked some but it’s hard to determine if the lights flashed less because of this strategy or because it was just the loose connection behaving itself more.

So - the question - assuming something is actually at fault, and given the E-brake is released, the voltmeter is happy, and the A/T is the question mark, what might a warm transmission indicate? I have an infrared temp meter, would measuring the external case temperature be useful? Should I just get the tranny serviced and the filter replaced?

Am I right in thinking the Brake(!) light (it has the exclamation mark) is just the E-brake or is related to the whole active braking system? The brakes are a bit soft right now but I’m blaming that on wear and tear - I need to get the front pads serviced and at least one rotor replaced.

FWIW: I have an aftermarket tranny cooler attached although its radiator seems small and has been installed flat to the underside of the vehicle and not up front at the grill.

Ideas?

2

My former 1988 4-Runner used to have its Brake! light flash on and off every couple of months. When it did, it needed brake fluid. Topped it off and I was good for another couple months.

Why the A/T Oil and Battery lights would be flashing too is beyond my expertise, though.

On further reading the OP, you said that it does it when the engine is warm. Could it be the heat from the engine is causing the connection to swell as it gets warm, adjusting the short?

In a related hijack, I will say that my current 2000 4-Runner has the right half of the heat/ac dash controls backlighting is out, and the radio backlight went out with it. Still have the left side of the heat/ac control backlighting. Same thing happened to my father’s '01 4-Runner* (we’re a 4-Runner family). Anyone out there have a suggestion?

  • He now drives an '06 4-Runner. Jerk.
3

The brake warning light is normally activated by both the handbrake lever being on and the brake fluid level in the reservoir being low. Either can turn on the light.

But those three lights are wired together with diodes. It’s been my experience that on many Asian cars (maybe just Toyotas?), when the alternator fails both the charge (=battery=alternator) and brake warning lights come on. It might be that the A/T fluid temp light will also come on with the charge light (most cars don’t have the A/T light, so I haven’t observed this). I would say the prime suspect is an alternator whose brushes are so worn that they sometimes lose contact. To check this, leave the engine running when those lights are on, and check battery voltage. If it’s 13 volts or less, and going down slowly, there’s no charging. Alternator time. For a double check, whack the alternator with a screwdriver handle and see if the voltage goes up to 14 or more and the lights go out. If so, that confirms it.

4

Nuke it from orbit it is the only way to be sure.
In my experience warning lights are often fed off of a common power, and have individual grounds. An example would be:
Oil pressure, ammeter, and coolant temp all fed off the same fuse. From the bulb for oil pressure is a wire that grounds when the pressure is low. From the ammeter is a wire that grounds when the alternator is not charging, and the coolant temp bulb has a wire that grounds when the coolant is too hot.

On some cars there is an arrangement (using diodes) that causes all of the warning lights in the circuit to illuminate when the key is on, and the engine is off. This acts as a check for a bad bulb. (turn the key on, and if the coolant light does not come on, this indicates a problem).

In your particular case, I would tend to think that the wire leading to the alternator from the battery warning bulb is grounding out intermittently. Every time it grounds it illuminates all the bulbs on that circuit. This may not have an effect on alternator performance. It should be fault traced and repaired, as harness that have a wire grounding tend to get worse over time, and the next wire to ground might cause a major loss of function.

The fault could lie in the cluster (not too likely) or under the dash, or in the engine compartment. Get someone to sit in the seat and start wiggling the harness with the engine running. If you can find a spot where movement of the harness causes the light to come on and off, you have found it.
Good luck.

I bow to Gary T’s greater knowledge of Asian cars, and concur with the recommendation to check the charging voltage first.

5

Have tried smacking the dash when the problem occurs to see if that has any effect on the problem? I had an '88 Lincoln that had a similar problem and when I smacked the dash it would correct it (until I hit a bump or something).

6

Yeah - smacking took place and I couldn’t make get any good reactions (other than a sore hand).

Oh - and I checked and the brake fluid is nicely full - no problems there unless it’s the float - which seems to move freely.

I’ll run the alternator past the auto-place and have them stick their gizmo on it.

7

I used to have a 1990 4Runner too! It was slightly lifted and had lots of rugged modifications. Boy did I love that thing. (Not me in the picture, it’s my 6’6" friend.) I took that thing everywhere.

It did have a lot of electrical problems though. The e-brake brake light was on all the time, for some odd reason, and there were also occasionally problems with the electric starter. The off-road lights malfunctioned sometimes, although that might have been an installation error as they were aftermarket. But overall it was a dependable vehicle. If I had known more about auto maintenance I’d have tried fixing it myself when it blew a power steering leak, but instead I just sold it. A hippie came all the way down from a commune in Colorado to tow it away behind his truck. That’s dedication.

8

Which suggests that the problem is not an electrical connection in the instrument panel.

You’re barking up the wrong tree here. The way the diodes are oriented in these circuits, the activiation of the charge light can cause the brake and A/T temp lights to come on with it, but neither the activation of the brake light nor the activation of the A/T temp light will cause any other lights to come on.

You’ll probably not learn anything unless the warning lights are on at the time. When the lights are off, the alternator is (presumably) charging and will likely test good. Test equipment can’t tell if the brushes don’t always make contact, it can only tell if they are making contact during the test.

9

Just to make sure I’m being clear here:

Alterntor problem = charge light, brake light, A/T temp light

Brake problem = brake light only

A/T problem = A/T temp light only

So don’t waste any time or energy on looking at or thinking about the brakes or transmission until it’s been determined whether or not there is an alternator problem.

10

Update: I took the truck by my local auto parts place and their test gizmo says my alternator is just fine.

Further update: the dash lights flickered at the truck’s start this morning. So much for the warm engine limitation. They also stayed off all the way into work - unusual.

EDIT: Thanks Gary. No lights flickered during the store’s alternator test so maybe no good diagnosis there. Also, I noticed my windshield washer isn’t working today. Either I gummed up the spouts with polish this weekend or my pump is not being turned on.

11

Get a voltmeter, and when the lights are flickering read the voltage across the battery terminals. As Gary T said if it is 13V or less, you have an alternator issue. If it reads above about 13.7 your alternator is OK, and it is a wiring issue as I described in my post above.
You can buy a cheap volt meter from Radio Shack for probably $10. Way cheaper than either a tow when you are stranded from a dead alternator, or buying an alternator when that is not the problem.

12

I will second the suggestions to ensure that the battery and alternator connections are secure and that there is a solid negative ground. After that, the suggestion to whack the alternator while the lights are on is also a great suggestion.

IME, as the alternator brushes wear, they can hang up intermittently in the brush holder. A solid whack will usually re-seat them, but eventually the brushes will need to be replaced. Nippondenso alternators in these trucks are usually good for a lot more miles, so it is cheaper to just replace the brushes.

13

Well, FWIW, the voltmeter on the dash dances nicely when the lights are flickering. No voltage numbers since it’s marked just with go/no-go bars but it does show something is happening here.

A short would read as no voltage, too, so is the voltmeter, either on the alternator or on the dash, a reliable way to differentiate between an intermittent short and an alternator issue?

The truck has a quarter-million miles on it but I don’t know how many are on the alternator.

14

Well since I have no idea what part of the electrical system Toyota wired he voltmeter into, and since a chaffed charge warning light wire could be right next to a chaffed voltmeter wire, and the gauge is not calibrated, no it isn’t much help.
Measure the voltage at the battery when the problem is happening. This will allow us to get a handle on the problem.

15

As a long time Toyota PU/4Runner owner I can confirm GaryT’s upthread observation that the brake and charge dash idiot lights are wired togeter, or at least that a charging system fault always activates both lights. Never had or fixed one with A/T so I dunno if that would also be lit up.

My bet is still on alternator brushes.

16

This is an aging thread but I’ll bump it with the results.

Simply put - bad alternator. There’s another thread where I was trying to diagnose the bad replacement alternator I bought but a working one fixed all.