When or when not to relay...

[Chris W]

Neils

 

Why at 8 amps? I have some really neat small switches from Vehicle Wiring Products which are rated at 16 amps continuous. So unless it's for one of the other reasons stated at the beginning of this thread, like keeping cable runs short, there is no inherent advantage to fitting a relay if the switch can cope. Plus one has the added expense of the relay itself, more complex wiring and a second point of failure.

 

For example Caterham don't use relays on the heated screen, wipers, radiator fan or hazard flashers, which all draw considerable current. In fact the only reason they use a relay on the indicators is to sense when the ignition is ON. This relay is bypassed by the hazard switch when that switch is operated. The only reason a relay (in the MFRU) is used on the fuel pump circuit (EU2 & 3) is to sense when the immobiliser has been disarmed. Both of the latter are of course great reasons for using a relay.

 

So I wouldn't say 8 amps is a rule of IMHO, more like it's horses for courses.

 

Chris

 

1.8K SV 140hp see it here

 

Edited by - Chris W on 3 May 2003 21:04:43