Relays and Euro lights

Tue Jun 4 09:34:00 EDT 2002

[ Picked text/plain from multipart/alternative ]
Just read this one....  The case of "new" spec vs element exposed reality.
The problem with relays is they have a life, specifically, they have a half
life.  The harsher the environment they operate in, the shorter the half
life.  In the case of my "underhood" installed relays in my urq for instance,
the crap wiring job from alt to relays located them right beside the radiator
(heat and water/salt).  Which reduced the half life of my relays to less than
two months.  When these pups get hot and/or wet, there is no guarantee of
spec.  In fact, in my case '83 urq, the relays would randomly arc closed,
this is *with* a 30 amp inline fuse (then run the battery down).  This
wouldn't happen if it was sunny, pretty much a guarantee if it was
raining/snowing (after shut down the lights would either stay on, or the heat
buildup would turn them on in the middle of the night)

I put up with this for 4 changes of relays in 6 months, until I recently
moved and properly mounted them in the glovebox area, and strung 10/12guage
wire from the battery.  Nary a problem since.  The problem with applying
200amps relays is a couple fold.  IF your relays are marginal (not new) you
DO risk the chance of not only arcing them, but welding them closed AND
blowing the bulbs out.  I'm only sharing BTDT.  I assure you Bernie, I have
and understand  the operating specifications of *new* 12v 4pin relays.

I'm only sharing what I see in practice, and personal experience.  If you
routinely replace your relays *before* failure, your theory/specification
applies.  IME, few routinely replace relays before failure.  In the land of
winter salt, underhood relays fail quite regularly, so do those high amp
unprotected connections between relay and wiring.  Mounting them near the
battery post means you put them near the hottest heat generator too (turbo),
which means half life ain't great.

"Don't fix if it ain't broke" - ok, but when it does, "Fix it right the first
time" (?)

My .02

Scott Justusson
practical relay install specialist

In a message dated 5/31/02 3:20:11 PM Central Daylight Time,
b.m.benz at writes:

Do you normally jump start your car with the headlites on?  200 amps will
flow through a discharged battery with an applied voltage at the jump
terminal of less than, or very little more than the normal system opperating
voltage, and rapid chargers are voltage regulated, restricting the peak
applied voltage to about 15 volts.  They are designed to be idiot proof!
Further, the arc over voltage of an open relay is well in excess of 600


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