16 April 2018

Whether or not the alternator gets swapped out, it looks like its wiring needs revisiting. The alternator connects through the fuse box to the battery. The catch is, I added a battery cut-off switch upstream of the fuse box and bad things can happen if the switch is opened with the engine running. At best, the engine quits as it should, though I now think it won’t. Since the alternator feeds in downstream of the switch, it would likely self-power the system and the engine would keep running. At worst, not only would the engine keep running, but with no voltage reference, the alternator could generate voltage spikes high enough to damage the ECU. I’m too chicken to try it and find out.

The alternator feed-in point needs to moved directly to the battery. As a related issue, the wire connecting the alternator to the battery is way too small (I blame the Painless Wiring kit but should have known better). It’s 10-gauge but needs to be much larger; the PowerMaster site claims that a 7-ft wire running 125 amps requires at least #6, if not #4. Yes, 125A is extreme, but having everything on in stop-and-go traffic with a flat battery could get there, albeit briefly. Wire size doesn’t seem like it could be the sole cause of the voltage drop, but it can’t be entirely ruled out either. Copper has a positive temperature coefficient, meaning the hotter it is, the more resistance it has, which causes voltage drops with current (this is why a hot starter won’t crank an engine). Still, air temperature rising only 20C wouldn’t be enough to account for the problem… only there’s more to it. The alternator wire runs down the center tunnel, sharing space with the coolant pipes. There’s a fair chance that it’s seeing around 60C or so, increasing resistance by around 16%. That still doesn’t fully explain the situation because the wire temperature in the center tunnel likely doesn’t vary much. Guess I just have to try it to  see; right now I still think there’s still a good chance the problem is an overly-sensitive voltage regulator in the alternator. Regardless, the alternator wire needs to be upgraded no matter what alternator is used, so this is a cheap experiment before spending money on other things.

15 April 2018

Received the replacement coolant temperature sensor and finally checked its calibration… well, let me back up.

An authentic Honda coolant temperature sensor is roughly $45 online, and me being a cheapskate, looked for alternatives. Found one on Ebay for about $8, with the picture showing the sensor next to an authentic Honda part bag with the correct number on it. I knew better than to think it was actually what the picture portrayed and bought it anyway. Sure enough it arrived in a plain box with no markings whatsoever, so no surprise it’s a knockoff.

Boiling water in a Thermos was placed in the engine compartment where the wire harness could reach. The new sensor was plugged in, and it and an accurate mercury thermometer were submerged  in the hot water. The sensors were allowed to settle for several minutes and then the temperature read; the thermometer settled out at 91C, while the sensor read 77C. Sigh, it wasn’t expected to read exactly right but this is kind of ridiculous. To be fair, I don’t know how accurate an authentic Honda part is, but doubt it’s that bad. We’ll see since a “real” sensor has been ordered.

14 April 2018

Took Midlana and the granddaughter to the new Cars and Coffee location, currently  at the Outlet San Clemente mall (one can only wonder how long it’ll be before they get thrown out from there as well, which seems to be the fate of the event, for noise, exhibition of speed, etc). This was the first time she’d been to any car show and, it went about as expected, not much interest, but the point was to expose her to it at least once so she knows they exist and what it’s about. I told her that I’d be happy to take her again but she has to ask – I won’t pester her to go.

No good deed goes unpunished and the traffic for the 50-mile trip home was brutal. The clutch was used about a million times because even at idle in first, Midlana wanted to move along faster than traffic. Being around 28 C didn’t help but it was a good test of the updated cooling system; coolant got up to around 90C but no higher. On the way up it was the exact opposite temperature-wise, dipping as low as 6C, brrrr. With such low temperatures, engine coolant only got up to about 80C.

Speaking of that, I’ve been watching how alternator voltage varies with temperature. In cold weather, charging voltage is 14.1V, perfect, and turning on the radiator fan caused it to drop to about 13.5V, still pretty good. On the way home in the heat though, charging voltage slowly dropped off to around 13.6V and dropped to 12.9V with the fan on. I was going to check to see whether the Chevy pickup alternator I’m using has an “S” input (Remote Sense). As I type this though, I just realized it doesn’t matter if it does or not. If there was a voltage drop problem at higher air temperature, it would still be there in cooler weather, but the problem is only during warm weather, ruling that out. It’s not like the alternator is being overheated either; right now there’s neither an engine cover nor belly pan. Also, since this is a cross-flow engine with the alternator on the intake side, it’s not near anything hot. I suspect the built-in alternator regulator just isn’t very good over temperature.

I could try running a cold air hose from the side vent to the alternator, but related to the above, since it’s already fairly well ventilated, there’s a good chance that the “cool air” being fed to it through a hose from the outside isn’t much lower than the air already swirling around the engine compartment. Of course, zooming way out on the problem, I’m not sure how much it matters. That is, it’s been this way for years and hasn’t been an issue, though I do keep a battery tender on it when in the garage. Then, during the endless traffic jam yesterday, I managed to stall it once and forgot the radiator fan was still on; when cranking, the battery clearly wasn’t happy at all about having to run both (sounding like a run-down battery). So there’s several approaches: do nothing, get the aftermarket alternator and hope it’s less temperature sensitive, or set up a cooling air duct for the existing unit and hope the outside air is a lot cooler than engine compartment air.