euro light relay question

[Harten Eric C Capt AWFC/TD]

I have put relays into my 1995 90 for high-watt bulbs and eventual euro
light conversion, but they have been doing some weird things lately.  I did
the standard thing with using the existing headlight sockets to power the
relays.  All worked well at first.  The only problem I had was that since
the fogs and high-beams used the same ground, I had to pull the fog relay to
let the high-beam relays shut off properly ( they had been sticking on due
to a residual voltage).  Now, on what seems to only be hot days)  the relays
will not come on sometimes.  They just start to buzz.  During this
condition, when I turn on my lights, the high-beam dash light comes on very
weak (no light and a buzz).  When I turn on the high's, the dash light
brightens up a bit but still no light.  I then pulled the new high-beam
relay and just left the low beam relay and I have not had a problem for a
couple of weeks.  Have I developed a short?  But, why the apparent thermal
effect?  Cooked relays in 120 deg heat?  Some ground I have not dealt with?
Each relay has it's own chassis ground.  I have checked all the pins with a
multi-meter and all the voltages checked out.  Any ideas?  

Eric

1995 90SQ
2001 A41.8T