[Decide]

Hey guys,
I want to run a switch in the cab that can turn on the A/C thermo fan (for a little bit of extra cooling). I still want the fan to run as normal when the A/C is running but want the ability to turn the fan on if im not using the A/C.

Would the best way to do this be to find the relay enable wire for the A/C fan relay and connect that to one side of a switch, the other side of the switch to 12V+ (ignition or cigarette)?

Car is a 97 vitara, 1.6L
Cheers

[christover1]

I put in a to earth switch , in place of the over temp cut out.

The over temp cut out sender is on thermostat housing, down the side.

Its job is to turn on AC fan and disable the ac pump if motor gets hot.

I used the hole to run a 2nd temp guage.

Now when I turn the switch, ac fan comes on, regardless of ac being on.
But if ac is on, it disables the pump.

Down side is, you lose the overtemp cut out, so have to watch temp yourself

hope that made sense, me brain fogs up late at night

[christover1]

PS. I can't see a reason not to leve temp sender in place, and run a 2nd earth thru a switch? but I not a sparky

[Decide]

Yeah I see what you did there.
I would prefer to just be able to kick the fan without messing with any of the over temp or anything like that.
I think splicing a wire into the relay enable wire is my best bet

[Bugsta]

You want to be careful routing power directly through switches. They have a limited current capability.

If all you want to do is switch it off and you can find the 'relay enable wire', no need to add an extra earth (or power), just insert the switch into that line. ie. run a fig8 and it just becomes a loop through the switch in series.

[want33s]

christover1 wrote:

Now when I turn the switch, ac fan comes on, regardless of ac being on.
But if ac is on, it disables the pump.

Down side is, you lose the overtemp cut out, so have to watch temp yourself

hope that made sense, me brain fogs up late at night

The other downside is your AC won't work as well or as often if the fan is working because the TX valve (high - low pressure switch) will cut it out.

[Decide]

Bugsta wrote:

You want to be careful routing power directly through switches. They have a limited current capability.

If all you want to do is switch it off and you can find the 'relay enable wire', no need to add an extra earth (or power), just insert the switch into that line. ie. run a fig8 and it just becomes a loop through the switch in series.

No I want to turn it on without having the A/C running, just the fan. I would only be using a fused 12v (ie cig. lighter) for the power to enable the fan, not power to run it directly.

[christover1]

want33s wrote:

The other downside is your AC won't work as well or as often if the fan is working because the TX valve (high - low pressure switch) will cut it out.

Mine seems to work ok.
But it is my 1st ever Air Con, so maybe it don't.?

Is the overtemp cut out a sliding scale sender? or just off and on.?

All I know is the sender is earthed,
and if wire is disconnected completely the AC fan comes on permanently
(even if ac is not switched on)

When I flick my switch, it disconnects that earth and fan comes on without air con going.
If I then flick it off, it reconnects the earth, then fan goes off.
But when air con is switched on the fan comes on/off with the air con pump.

Is this right?
I have no idea.
I could easily wire sender back in,
if I can locate a new place for my after market guage sender.

[Bugsta]

Ok. Easy. All you need is a double throw switch (SPDT). The centre pin goes to the fan. Circuit 1 to the original wire. Circuit 2 to either 12v or earth depending on which relay wire you choose to use. If you want the option of switching it off, make it a Centre Off switch.

[want33s]

christover1 wrote:

want33s wrote:

The other downside is your AC won't work as well or as often if the fan is working because the TX valve (high - low pressure switch) will cut it out.

Mine seems to work ok.
But it is my 1st ever Air Con, so maybe it don't.?

Is the overtemp cut out a sliding scale sender? or just off and on.?

All I know is the sender is earthed,
and if wire is disconnected completely the AC fan comes on permanently
(even if ac is not switched on)

When I flick my switch, it disconnects that earth and fan comes on without air con going.
If I then flick it off, it reconnects the earth, then fan goes off.
But when air con is switched on the fan comes on/off with the air con pump.

Is this right?
I have no idea.
I could easily wire sender back in,
if I can locate a new place for my after market guage sender.

As long as when AC is on, the fan is going when the pump is it should be fine.
I'd imagine the overtemp setup to be just open/closed.

[royce]

Why does any thread about power in this place make my head bleed?

Christover, your way works and wont hurt anything but isnt great, like you said if your switch is on you cant have AC

Bugsta, you NEVER make it so the AC can run with no fan, the pressure can go way high and shit goes pop, plus your switch setup is too complex and your first idea missed the point

Decide, depending on a lot of factors, like if its factory or aftermarket air etc etc your method may or may not work youll just have to try
find the relay that controls the fan, then poke around to work out if its positive or negative switched and then add power or earth to teh right pin to make the fan come on while youve got the AC off, but make sure when you do it it doesnt cut the AC compressor in at the same time (often whatever controls the compressor also turns the fan on with the same circuit)

the simplest way around this is fit a diode in the original switch line with the band pointing towards the earth side of current flow and hook your switch wire up on the relay side of the diode