Bongo Fury

Curious one this, grateful for any input.

I made a new section of the long steel pipe joining the two heater matrices. I then filled the coolant system with water and ran the engine for about 45 minutes. Unbelievably, the head gasket seems to actually be sealing, coolant level doesn't drop or overpressurise and there's no coolant mixing with the oil. Engine runs sweet as a nut.

I'll still be doing the head gasket anyway, the boroscope shows the fire rings in all cylinders have burned sections which will definitely fail completely. I got the torque specs I needed from a Kiwi forklift repair place. I'll leave it up to my friend if she wants the rings and notes done. The compression figures hot were better at 100 psi 3 and 4 so 85 on 1 and 2, but that's still seems very low.

Anyway, while running the engine, the charge light was continuously lit. I tested the alternator output at the alternator and at the battery and it shows a good 14.6v running and 12.3v with the engine off. I don't see any wires broken or loose. Anyone have any ideas what the issue might be?

For the sake of interest, here is the rotten pipe that dropped all the coolant, complete with someone's lovely JB Weld bodge and the replacement I fabricated up.

The charge light is controlled directly by the alternator, it provides an earth once the alternator is running and operating see diagram below; The light is driven from the connection off page far right
Hence it might be worth checking further with the alternator itself.

Thanks,I'll look at the alternator again although I definitely didn't see any loose wires or connectors, unless it's a fault internally to the alternator, in which case, I don't have the expertise to diagnose. It's certainly charging well and regulating the charge voltage as well, it didn't deviate more than a couple of tenths of a volt regardless of the load.

I've got Mazda dealer level diagnostic software, I can plug it in and see if it comes up with anything but I doubt it will give me anything useful due to the age, it's a 2003 Japanese import.

I don't know if the light was on before the van got delivered to my farm or if it's a new thing because I didn't run it until I'd fixed the coolant pipe, I'd only turned it over for the compression tests. It's possible the garage my friend took it to previously did something, although AFAIK all they did was a compression test.

It certainly wasn't on when I checked it before it went to the garage, as I was specifically checking the charging for my friend as shed described sluggish starting (although it turned out to be partial seizure due to running without coolant.).

It could be an earthing fault on the wire going to the lamp, or a fault inside the alternator, not able to give much more advice as its a rather simple circuit! +12v - to lamp - to alternator and switching to earth.

I'm guessing it must be a fault internally to the alternator. The wires coming out of the alternator go straight into conduit, so the wire is unlikely to be shorting against the body. The fuel gauge appears not to working either but probably not connected.

At first glance it looks like it could be the same alternator that's on my MX5, so I'll maybe swap them over to check once I've got the head off. Concentrating on getting that done so I can get it skimmed and built back up. I'm confident it's not cracked at least because it's run for a good 1½ - 2 hours without losing coolant