Intermittent dash lights... (1 Viewer)

[ChaseTruck]

A/T Temp, Brake, Oil, Charge...

If this is indeed the alternator, I'm not going to be very happy.
This would be Sequoia alternator #2, lifetime of ~ 5 years. Similar to the first one , changed that one out after it did start to over-charge.
Both of these were new, fresh from Toyota... I do hear a belt squeal every now and then, and no, it doesn't coincide with the dash light show. Charge gauge looks ok when the lights are on. Shutting it down, battery reads 12.68V. I'm not quite ready to blame the alternator, suspect some other gremlin at work... And no, I don't feel like changing the fusible link just because.
Still - I've started to look for the stock alternator bracket etc., gotta be around here somewhere.

 

[jonheld]

Something in the charging circuit is unhappy. Possibly a bad connection.
I would be checking all related items with a meter, not my feelings.

 

[ChaseTruck]

Something in the charging circuit is unhappy. Possibly a bad connection.
I would be checking all related items with a meter, not my feelings.

Agreed. When I wrote the post, everything under the hood was still too hot to touch.
Plan is to wiggle connections with engine running and someone in the driver’s seat to keep watch if the lights come on. Then, with a cold engine, unplug, spray with contact cleaner.

 

[ChaseTruck]

Ok. First bit of information.
I got the dash light show again a few times on a short drive this morning, mostly under torque. Revving the engine in park, I managed to get the lights back on in the driveway, and connect the voltmeter - 13.94V with the engine idling. Hm, a bit low; normally it's 14.4V. Wiggle the plug at the alternator (heat protection courtesy of Harbor Freight welding gloves...) - voltage goes up, and then keeps jumping between 14.6V and 15.6V. I think I have identified one part of the problem.

 

[sbman]

Ok. First bit of information.
I got the dash light show again a few times on a short drive this morning, mostly under torque. Revving the engine in park, I managed to get the lights back on in the driveway, and connect the voltmeter - 13.94V with the engine idling. Hm, a bit low; normally it's 14.4V. Wiggle the plug at the alternator (heat protection courtesy of Harbor Freight welding gloves...) - voltage goes up, and then keeps jumping between 14.6V and 15.6V. I think I have identified one part of the problem.

15.6 is too high. You probably need to replace the alternator connector and terminals, obviously wiggling it should not change the output voltage.

 

[jonheld]

Ok. First bit of information.
I got the dash light show again a few times on a short drive this morning, mostly under torque. Revving the engine in park, I managed to get the lights back on in the driveway, and connect the voltmeter - 13.94V with the engine idling. Hm, a bit low; normally it's 14.4V. Wiggle the plug at the alternator (heat protection courtesy of Harbor Freight welding gloves...) - voltage goes up, and then keeps jumping between 14.6V and 15.6V. I think I have identified one part of the problem.

Couple of thoughts.
Alternator output voltage will vary depending on the state of charge of the battery, however the max voltage should be 14.4 or very close to it. If you're seeing 15.6, then the voltage regulator in the alternator is faulty.

 

[ChaseTruck]

Pulled the plug on the alternator; didn’t have any contact cleaner, so I used a good squirt of WD40, followed by a stream of brake cleaner, then WD40 again, and clicked it back in.

No light show after starting, voltage at battery 14.15V. Just back from a 90 mile drive (to get the truck that’s been sitting for a month ready for the emissions testing). Still no light show…

So far so good. But: truck idling, coolant temp 190, outside temp 104, voltage at battery 13.75V…
Wiggling the plug doesn’t have consequences for voltage.

Agreed that 15.6V is too much. The first Sequoia alternator that went in that truck maybe 10 years ago did that, as well, after about 5 years. Not quite sure how to think about this just yet. I mean I’m pleased with the plug fix, but not sure that’s the entire story.

 

[robnicko]

The symptoms described sound like the regulator may be at fault however I would also be looking at the brushes.
When the brushes went on mine I got all the dash lights however a gentle tap with a hammer on the side of the alt freed them up and it started charging again & dash lights went off. Changed the brushes and been fine ever since.
Note that if you were driving whilst all the dash lights came on and no charge from the ALT the battery will be doing all the work and then once the brushes free up and the ALT starts charging again it will be trying to put as much power back into the battery as possible so can show higher readings.