etdavenport

I am working on a 1990 4 runner SR5 [22re, 2.4L]

Strangest thing going on. I recently installed a slightly higher output alternator on my rig. I run a lot of auxiliaries. WE live out in the bush in , Dillingham, Alaska. It gets cold. About a month after I installed this new alternator, when the temps outside started dropping below about 5 degrees [its -22 now] my brake and battery light started coming on [alternator] when we parked the truck outside at night.
When the lights come on, the alternator output drops significantly but will still power the truck. Lights are just a bit dimmer, heater half working etc. but the battery does not drain. The alternator is still giving a consistent output, its just about 2/3's what it is supposed to be. Once the engine compartment warms the thing up enough, everything kicks on and it works fine. If we park the truck in the garage over night, no lights, no problem, but once we go somewhere and let it sit in the sub zero temps for a short time [wife parked it for 20 minutes in -20 and the lights came back on again]. So it is defiantly the temperatures affecting alternator output, not battery voltage.

I have checked the belts, replaced the battery [tested the battery output before and in the morning cold, not the battery...]
Cleaned the grounds on the side frame, back of engine, starter ground, the one on the power steering pump and the wires from the fuse box and diagnostic box.
check, cleaned and double checked the alternator connections. battery terminals etc.
checked coolant levels etc [recently had to clean adjust IACV half a year back to fix idle issues, so everything there is good]

I am waiting on a buddy to send me out another working alternator to see if the issue persists.

I have never heard of cold doing anything like this to an alternator. I have replaced or ruled out moist everything else. When the replacement arrives, I will know for sure, but I wanted to ask the forum if anyone has encountered anything like this. Maybe I missed a wire somewhere in the charging system? Is there a ground I am not finding?

Thanks!

RAD4Runner

How much drop?

Desired readings listed here:
https://www.yotatech.com/forums/f116.../#post52401963

etdavenport

Quite a bit. Far beyond the normal dip when using blinkers, heater, lights etc. The truck gauge normally rests to the far right [about 18 i think?], it drops to just below half way, outside of normal operating range. On a multi-meter it goes from about 16-18 volts [nothing running] to about 10-11.

RAD4Runner

Yeah, significant, so there's definitely a problem, but you need to take readings at different points like I listed ion my post, and tell us exactly where, in order for us to tell what's going on. AND take readings without load and with STOCK load, else we have no point of reference. Perhaps the problem is your load.
I assume you took connections apart and made sure you have bare, shiny metal tightly agains bare, shiny metal.

scope103

16-18 is really pretty high, even for a low battery. The standard is 13.9 – 15.1 V at 25°C http://web.archive.org/web/201102051.../2onvehicl.pdf I don't have much experience with really low temps (the standard charging voltage goes up with decreasing temp, but not that much). But 18v, if your multimeter is accurate, could damage the battery. Similarly, 10-11v with "ordinary" loads is WAY too low.

So DO check the voltage right on the battery posts, and compare that to somewhere on the clamps. If you have an iffy connection to the battery, the alternator doesn't accurately sense the battery voltage (so keeps raising the output voltage), and when the alternator kicks out your (otherwise charged) battery has a big voltage drop through that connection.

If the clamps aren't the issue, as Rad4Runner suggests, work your way through the electrical system to find the bad connection.

RAD4Runner

+1
Would happen if the S (thin white wire) is not making good contact with the thick white B wire. They're crimped somewhere near the engine comp fuse block.

millball

Might be that the current limiter in the voltage regulator acts up at extreme cold.

I'd replace the reg. and see if there's any improvement. Shouldn't be too expensive.

etdavenport

Thanks all. good stuff. I will get back after I go through the steps in RAD's post.

millball

Any further determination as to the nature of this problem???