[shandy92]

Hey all, just wiring up a manual override switch for my a/c thermo fan. I plan to run a relay for it but just want to be certain that it is required???

Think its a bit scary having a big pos wire in the dash. Altho i cant neg switch it because its earthed on the a/c side, i still have a pos line up to the switch. Sound ok or have you got a better method?

Cheers

[johnmath]

Wouldn't there already be a relay for the A/C fan? If there is, you can probably just add another control wire, either +12 volt or ground, depending on how the original relay is controlled. Have you had a look at the A/C wiring diagram? Maybe someone here to point to where to find it for you Vitara(?).

[shandy92]

Yeah there is, but im pretty sure the comp runs off the same relay. Its an aftermarket system with very messy wiring. The two relays for the a/c use plugs not individual connectors. So not really easy to tap into. Good idea tho, will look into it more.

[johnmath]

You could use just a switch because the fan will pull something like 10A or so, but most switches won't last long switching that much current. You probably should add another relay just for the fan so that you can isolate it from the compressor. You might need to diode isolate the relay control so that your aux switch doesn't feed +12 volts back to something else.

You might be able to use or adapt this wiring: http://www.davebarton.com/pdf/coolingfandiagrams.pdf

[shandy92]

Hey mate,

I went to the local auto sparky to get some relays and told him what i wanted and he pretty much did the entire thing for me in the end. He took power from the relay and like you said used a diode on the comp. While he was there he also fixed the rest of the A/C system, so now my a/c actually works when i tell it to instead of when it feels like. The entire system was full of bad earths and connections.

[Gwagensteve]

That's a good outcome.

I'd recommend putting a really, really bright light on the dash when you have the switch manually. If your cooling system is working properly, it shouldn't really be needed, so the override should only be there for short periods/ in an emergency.

If you don't have a really obvious visual clue you have the switch in manual mode, you'll forget and leave it on, masking the real performance of your cooling system

Steve.

[SierraDan]

On my Sierra I managed a habit with my thermo.
It had a flip switch with a light in the end of it, as an indicator it was on. But without thinking I had a habit of putting the car into low range, then the thermo straight afterward.
Long painful steep hills, I'd change back gears then flick the thermo on.

Before any temps can even begin to think about rising i would have preemptively bumped up my cooling.

[alien]

^^ i do similar... my temp goes up (nothing serious, but gets to 90*C / half way on the gauge) in summer on long slow crawls, so i switch on the thermo pre-emptively when the needle starts to rise above 1/4 (which is where it normally sits). I don't have any visual clues though - but mines wired right off the battery, so it runs when the engine is off. Very obvious when you're 4wding as you frequently switch off to help someone up a section or to walk a bit of track, so the whirr of the fan is easy to hear once you turn off the motor.

[shandy92]

Steve, i dont really need it as my cooling system is pretty new and doesnt give me any dramas. It is only there for back-up or if im going to be in 1stlow for any extended period of time.

Now how do i test how efficient the fan is actually going to be? Its a 12" spall fan sitting on the condensor, with the engine off and fan on there is a decent amount of air being pushed through the rad but how do i know if its going to be enough to make any difference? And have i just wasted my time.

P.S would it say the CFM on the fan?

Thanks.

[alien]

use a temp gun to monitor the temperature of the back of the radiator, that'd give a fair idea of if its doing anything pretty quickly?

[shandy92]

Yeah ok, simple enough.

[royce]

shandy92 wrote:

Steve, i dont really need it as my cooling system is pretty new and doesnt give me any dramas. It is only there for back-up or if im going to be in 1stlow for any extended period of time.

Now how do i test how efficient the fan is actually going to be? Its a 12" spall fan sitting on the condensor, with the engine off and fan on there is a decent amount of air being pushed through the rad but how do i know if its going to be enough to make any difference? And have i just wasted my time.

P.S would it say the CFM on the fan?

Thanks.

Compare it to the engine fan at 2500rpm and it up to temp so its not freewheeling, it wont be much, even a big thermo doesnt really touch the engine fan for flow.

But like you said its there and it might come in handy one day if the engine fan fails, or you need to leave it idle in hot weather or something.

[shandy92]

Yeah i understand that its got nothing compared to the engine fan, but i have it sitting there for the air con so why not have more control over it. I just checked and its actually a 10", might keep an eye out for a 12"+ fan and swap it over.

[fordem]

I don't know if you know this, but, the factory a/c systems will turn the condenser fan on (if the a/c is off) if the coolant temps get too high, and if the a/c is on, they disable the compressor clutch and leave the fan running.

No modification required.

[shandy92]

Yeah but its not a factory system, the comp cuts out but the fan doesnt engage.