Is the cluster in series or parallel with the rest of the circuit? If it is in series it’s possible that the cluster is your only problem.

Try taking the cluster with you so it doesn’t warm up, then plug it in and start the car before it can heat up to see if the issue disappears when only the cluster is cold.

Or better, try plugging in another cluster and see if the problem disappears. I’m pretty sure the milage will be maintained on digital odo.

This temperature factor makes me confident that your wiring is fine, symptoms make me think it’s a PCB issue.

Were later 4runners with manual hvac still using cables to do everything? That shouldn’t be affected by temperature. The AC is the only control that isn’t controlled with cables (on my 1998)

Mileage is on digital's is stored on the board screwed to the back side of the cluster.

Pwr to the cluster is supplied primary by the gauge fuse circuit by one wire on the backside of said, most of the light's and display info is supplied by this, while the light's are triggered by a GRD being supplied to what ever applicable circuit, to say that PWR is consent in the key ON/RUN position and the different circuit require a GRD to complete the circuit.

The Body ECU is not difficult to get to and remove but it's not "easy" either, sure u can find info on the procedure but my guess is this isn't ur issues (but I'm not there so...)

From what I gathered from other forum posts, the fan blower either shares a circuit or needs a signal from the combination meter in order to kick on. Can't really remember exactly what it was but it's something along those lines, though I guess I could check my wiring diagrams to see if that's actually true or not (probably a smart idea, not sure why I haven't done so already)

The only reason why I suspect it to be the body ECU is because that's the only common denominator between the dash, hvac, and windows. Seems much more likely for that to be affected than 3 separate things that are all spaced out from one another, but at this point I'm also grasping at straws so who knows

Anybody know what these connectors handle? Every wiring diagram I've looked at says the only connectors on the body ECU are in the back, not the front
(Those wire taps aren't mine, they were from the previous owner trying to hook up an aftermarket immobilizer)

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Those Connectors are connected into the body ECU, U clip them and then pull the cover off the said and ur body ECU is right there, I'd remove all those splices and check the wiring's condition and repair as needed, could b part of ur issue. Most of those wiring run to the steering column combination switches and center console controls, i.e. rear window up/down, fog light switch, etc

I'm well aware of all of that, the question is what the connectors are as the 2000 SR5 EWD doesn't list any connections in the front of the panel and says everything should be connected behind the body ECU - none of which are that shape or have that number of wires (the only diagram for the body ECU is under the section titled "relay locations" for reference). According to the connector list in the EWD the big one somewhat matches connector F7 but as far as I can tell it's not mentioned anywhere else in the diagrams for what it controls. The smaller one might be connector B17 (?) but same deal, can't find any mention of it.
The splices have been there for probably 10+ years now and I removed everything connected to them about 4 years ago, so I very highly doubt that's the issue.

"Component Location" - Connectors B16 and B17. Lots of the wires are on the Wireless Door Lock pages, and I'm sure you could find more on other pages.

-Charlie

Just came to correct myself and say it's B16 and B17, didn't realize the connectors were upside down

What are those red things around the wires? Did someone splice things into your harness?

Edit: You literally said in the post my bad. Look over any wiring that was messed with with a fine tooth comb, that looks very suspect.

Those vampire clips can break wires pretty easily, especially over time. This is definitely the first place to start with debugging.

-Charlie

Tool out the taps/splices, repaired the wires, threw in a new relay on the body ecu and new fuses all around - still no luck, lost power again this afternoon after about 5 minutes of driving, with the AC blasting on full no less so I doubt it's heat related like I suspected before. I happened to have a multimeter on me so I poked the 10A gauge and 10A turn fuse and got no resistance reading on them. I guess the only thing to do is start unplugging the ecu and poking various pins. Couldn't do it tonight as I was in the middle of making dinner so hopefully it'll come again soon and I can try.

The only other common denominator I can think of is it usually goes out when I have my left turn signal on, but that could also be because whenever I'm going somewhere I take way more left turns than right (sounds dumb but when I think about my route to work, the gas station or to the store it turns out to be true.)

Power into the body ecu is connector 1I, pin 2. Power sent to the combination meter from the body ecu is connector 1F, pin 8; turn signal is 1J, pin 5. I guess the next step would be to check the 1I connector and see if it has voltage, and if that isn't the case then the only other options would be to replace the 50A J/B fuse under the hood or the body ecu as a whole. If that doesn't work then I'm at a total loss because as far as I can tell, all options have been exhausted by that end.

Anybody know how interchangeable these fuse panels are? The part number on mine doesn't return any results, in fact they all seem to vary wildly despite there only being a few different models. I'm hoping if I get one identical to mine it'll fit despite there being different p/n's.