alternator not charging intermittant

[how1e]

patrol 2000 gu petrol TB45E
story so far.
alt noisy then dies 300m from home, battery flat, RAC give me boost and i get home.
next day, usual mechanic fits new alt, gets strange warning lights, alt giving out 17v.
next day, usual mechanic fits 2nd new alt, all seems good but then alt stops charging intermitantly. wiggling wires into the alt seems to fix the fault temp.
next day, usual mechanic fits 3rd new alt, all seems good for quite a while (over a week, but i stopped watching), then the last 2 days it gone intermitant again.
i know the alt isn't charging because the redarc LED i have in the cab goes out.
the alt charges when the motor is started and can continue for 5-10 minutes, then stops charging.
today i have tried a brand new battery (no difference) and used jump leads to earth the battery to the body (no difference)
after putting the original battery back, the alt started charging for about 5 mins then stopped again.
usual mechanic is coming around tomorrow (not with 4th alt)
any ideas?
i'm thinking sense wires or something electronic.
NB after fiddling around today, i found the 7.5amp 'alternator-S' fuse blown, replacing didn't change anything (or charge anything)
NB#2 at one point the battery warning light flashed on, together with the sub-tank warning light. (now i'm thinking earth probs)
NB#3 the battery warning light doesn't come on when i'm driving around, i have been monitoring the 'redarc' LED.

[my third 256]

i think auto electrician might be the way to go as they will have all the knowledge and tools to test

[threedogs]

can you isolate the redarc unit and test alternator with a multimeter

[mudnut]

You said "Wiggling wires into the alt seems to fix the fault temp."

Well check that again, as a small break in the wire or at the lug or a faulty lug, or a high resistance connection will, cause the voltage regulator to malfunction.

[how1e]

can you isolate the redarc unit and test alternator with a multimeter
the redarc is between the main & 2nd batt and has (IMHO) no effect on the alt.
the redarc only kicks in when a certain voltage is reached, so i just use the LED off it as an indicator that the alt is charging.

[how1e]

You said "Wiggling wires into the alt seems to fix the fault temp."

Well check that again, as a small break in the wire or at the lug or a faulty lug, or a high resistance connection will, cause the voltage regulator to malfunction.
the mechanic seemed to think there was definitely a fault inside the 2nd alt, although the fault condition is similar with alt#3, 'wriggling' the wires doesn't have any effect.
it's almost as if there's a timer on it, which also might make it heat related, which as you say could be a HR connection somewhere.