G
GW> JE> GW>
GW> JE>> one). Two types of flashers now. Then for vehicles towing a
GW> JE>> trailer with turn signal lights an even different flasher was
GW> JE>> needed - one that would operate properly (flashes per sec) both
GW> JE>> with and with out the trailer - commonly called a HEAVY DUTY
GW> JE>> flasher here. My 89 Ford van used this method as did most
GW> JE>> vehicles I came in contact with. I haven't looked at my 92 Ford
GW> JE>> Crown Vic nor my 92 Chevy PU - which I use to tow a trailer. The
GW> JE>> PU came with a towing package which may have included a flasher
GW> JE>> that takes care of the trailer. The trailer has two bulbs in each
GW> JE>> the left and right tail light.

GW> JE> GW>The towing package was probably no more than two relays to
GW> JE> operate the GW>lamps (one for each side) and a current sense relay
GW> JE> in the feed to GW>sense the trailer lamp current. These days this
GW> JE> can be just a winding GW>round a reed relay, the trailer lamp
GW> JE> flasher inicator is driven by GW>this relay. Probably set up to
GW> JE> indicate "good" if a lamp works, and if GW>there
are two it
GW> JE> probably won't tell if one of the pair fails.

GW> JE> Since the trailer light feed is a tap off from the rear tail,stop
GW> JE> and turn signal light of the tow vehicle (in other words in
GW> JE> parallel) how would a relay get into this picture? I've wired many
GW> JE> vehicles to supply the trailer lights - there is no way the
GW> JE> trailer lights can operate a second relay. ONLY the increased
GW> JE> current in the lamp circuits (tow vehicle and trailer combined)
GW> JE> causes the flasher to work. Sadly, I have never taken a Heavy duty
GW> JE> flasher apart to see how they work, simply because I have never
GW> JE> had one to fail and I wasn't about to take a good one apart. :-)

GW>If it is a dedicated flasher the rules are different. I was just
GW>talking about the kits I've installed in my family's cars when we
GW>fitted a tow hitch. They just tapped into the rear stop, tail and turn
GW>circuits too. However the turn signals went into a unit that also had
GW>a power feed (ideally ignition switched but it didn't need to be) and
GW>an earth connection (needed for the relays).

Seems like a lot of extra work and expense compared to what we do here.
We tapped into the turn/stop/running lights and connected that to a
receptacle that the trailer connector plugged into. No relays - period!

Jay
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