Alternator Issue?

[clubbyr8]

It's been a warm day in Sydney today (45˚ C). Driving home from the shops my alternator reduced it's output voltage, it varied between 12.1 and 13.6 as shown via the OBD2 plug. I was running the AC at the time and had a drink cooler running off the second battery. DRL's were also running. This is the first time this has happened but it was extremely hot in the engine bay. After I let everything cool down, I started the car and the reading was back to normal. Anyone got any ideas, or is it just a heat issue?

[PeeBee]

I would guess its heat related - higher heat resulting in greater resistance perhaps? I also think diodes are also temperature affected re performance - maybe a more electrically aware person can comment. I have had a similar thing happen to me, PIA and right on dusk, so headlights dragging the voltage down, but next day, all good. After that I ran a 12V ventilation fan , blowing engine bay air over the back of the alternator, used to ventilate boat engine bays, and never had the issue again. This was when I had the 2.8 TD in the GQ and the ambient temps were above 40 Deg C. No issues yet, fingers crossed with the chev.

[threedogs]

the guys running 6.5 TD chevs have plenty of under bonnet heat ,
never heard of any complaining of alternator issues.
but out of ordinary conditions could be the cause @Yendor.
Have you checked or re-newed any earths??

[clubbyr8]

I think I'll replace the battery and earth leads, anyone know what size they are?