fitting the override switch

[softtop]

I want to fit the ocerride switch as described in the bible but wanted to be sure before connecting. I tested for voltage with a simple tester and there was a positive voltage on one side of the switch on the radiator. Since it is switching to earth I did not want to short the two out as you would expect. Am I being over cautious?

[JonRB]

Before fitting an override switch you need to ask yourself why you need to fit one.

I had one fitted as I was suffering overheating problems and it was considered useful to be able to override the fans on when entering, say, a traffic jam and I did indeed find it useful at the time.

However, since then I have had a lower temperature themostat and otter switch fitted and I don't think I have ever needed the switch since.

Of course, it is nice to know that if my otter switch or thermostat ever fail then I can override the fans from the cockpit rather than having to dive under the bonnet to do it with the aid of a bent paperclip or whatever, but apart from that I can't really see a use for it any more.

[GreenV8S]

softtop said:

I tested for voltage with a simple tester and there was a positive voltage on one side of the switch on the radiator. Since it is switching to earth I did not want to short the two out as you would expect. Am I being over cautious?

Worth being cautious, but in this case shorting the 12V side to earth (or to the other side, which amounts to the same thing) is the right answer. You're pulling one side of a relay coil down to earth, the other side as 12V applied. When you earth it, the relay coil will limit the current to 50 mA or so.

[everitj]

Just a thought but when I was thinking of fitting an override switch, before the cooling system was 100% sorted I was thinking of connecting to the rear wiper switch on the wiper stalk which is not used. Saves cutting a new switch in. Just an idea I thought I would share...

[softtop]

Thanks I will check it out. Is it a permanent feed or intermittent?

[softtop]

quick update. fitted a replacement otter switch 82-92 and the temperature does not go above 80 now. Seems to have solved the problem. I did remove the number plate initially but it made no difference so I suppose it had better go back on! thanks for the help. The reason I thought about fitting an over ride switch was to help the air flow since the fan would be moving and not restricting.