cooling fans

Yes.

I would say Nope

I think you are saying you want to lift the fan motor grounding wire and connect to the thermal switch. that would require the thermal switches to carry the fans full amperage.

this arrangement would be AND logic. thus it would take both the console switch ON and a thermal switch ON for the fan to run. the console switch could be used to cut the fans OFF with a hot radiator.


the switches should be used to energize the relays where the coil current is much less (the reason to use a relay in the first place.

the drawing is what I think you are asking and is NOT recomended

quote:

Originally posted by Tomato Panscourer:...Can i connect the radiator fan switches to the negative wire from the fans without coming from the dashboard and still keep the rocker swich overide?

Thanks in advance

if the thermal switchs are wired to energize the relays, then the exisiting console switch would become an OR logic in that either the console switch or a hot thermal switch would run a fan. the console switch would then be used to run both fans with a cold radiator (or if a thermal switch failed)

I agree with JFB that drawing fan voltage through the switch could be a problem, and that the better way is via a relay. But if I'm reading the diagram correctly, the main voltage is still being pulled through the ignition switch, as drawn. I'd think this would be better avoided.

The main power input to the relays could instead be supplied from a non-switched (but fused) supply, while only the relay turn-on voltage could come via the ignition switch, thus sparing the ignition switch most of the load. When either the thermal switch/es or the manual switch grounds that relay circuit, then the relay closes and connects this non-switched supply to the appropriate fan/s.

Hard to describe... Hope this made sense.

quote:

Originally posted by MarsRed:
... the main voltage current is still being pulled through the ignition switch, as drawn. I'd think this would be better avoided....

I agree. something I have been thinking is to add a high current (50A) relay to provide the ignition switch run supply

Thanks chaps, thats a lot for me to get my tiny brain around, the fans are already wired through two relay's. What does bk and b mean, black and brown??I'm not good at wiring

from the wiring diagram.
I would use caution and not expect color coding to be absolutely true.

When you said you wanted the console switch as an override, would that be;
cut the fans OFF if the radiator is HOT
or
cut the fans ON if the radiator is COLD?

if the latter, then in words.
Take one side of the radiators thermal switch to frame ground, black wire.
take the other side of the thermal switch to the fan rely terminal where your console switch is connected. Don't know what color.
this wiring will let you use the console switch to cut the fans on if the radiator is cold or if the thermal switches fail

if you want to cut fans OFF if the radiator is HOT...I'll reply after.

Do you know if the two thermal switches are located in the radiator inlet or outlet?
Do you know the thermal switches degree setting where they close/open?

Thats great i can understand that but my thermo switches have only one terminal, i dont know the on/ off temperature settings.

In my experience, one-terminal normally-open thermal switches ground when they reach their turn-on temp. So you run 12v+ to the device and ground it through the thermal switch. When it reaches turn-on temp, the switch grounds the circuit and on goes the device (relay for fan). Installing a manual switch that can complete the ground will also turn on relay.

A (normally-open) thermal switch with two terminals will conduct between the terminals once it reaches turn-on temp. This type is what JFB was referring to, and why he directs you to ground one terminal.

I believe their turn-on temp will often be indicated on their base.