Hold On

Whats a good switched 12V source in the engine compartment, to feed an adjustable temp switch, to trigger a relay for some radiator cooling fans?

I want to stay away from the temp switch at bottom of radiator and not disturb the A/C aux. fan circuit.

hacker-pschorr

If you are using a temperature switch, isn't the whole idea to have that turn the relay on / off where you set it to based on coolant temp?

Or are you trying to make it so the fans shut off no matter when when the ignition is off.

Swapping the lower radiator switch is the easiest since there are multiple VW switches that are a direct replacement from Hella.

Is this for the front mounted fan? The pullers?.....

As for ignition sources there is at least one in the multi-pin connector above the jump start terminal (don't have a diagram in front of me).
Also an ignition switched lead that goes to the ignition brain, I wouldn't tap into that one though.

Hold On

[QUOTE=Hacker-Pschorr;8414858]If you are using a temperature switch, isn't the whole idea to have that turn the relay on / off where you set it to based on coolant temp? Yes

Or are you trying to make it so the fans shut off no matter when when the ignition is off. Yes also


I want to power the temp switch when the ignition is turned on. I will set the switch to trip relay and turn rear puller fans on approx.10 degrees above thermostat opening temp.

I dont want fans running at startup, during warmup or when car is moving at speed when airflow thru radiator is adequate.

I want temp switch to read hottest part of radiator at top passenger side, so it closely matches digital temp guage in car. Sender for that is located in top hose. That is why I dont want to use AC aux. switch at radiator bottom. Signifcant temp difference at that location.

hacker-pschorr

All good ideas but IMO you are drastically over thinking this.

Measuring for the fans at the output of the radiator is really the only logical place to do so.

The only reason to have fans is to compensate when airflow through the radiator is inadequate. The only way to measure this is by the output of the radiator. If the temps leaving the radiator start to climb, need to increase the airflow.

If the output of the radiator is sufficient and your engine is still running to hot, you have other problems.

Unless you feel the fans are running too much than put in a higher temp switch.

Hold On

Good point , I will look at this tomorrow when I do the install.

Everything is currently running well. Im trying to isolate the a/c cooling system, from the engine cooling system before the weather gets to hot. I had to install electric puller fans when the S/C was installed. The elec. draw is high, hence the temp switch and relay setup powering the fans direct from jump post connection.

hacker-pschorr

Do you have the original or any pusher fan on front of the condenser?

WallyP

If we knew what year model this is, we could also make some suggestions on the A/C control of the fans...

It appears from the photo to be an early car. If so, the A/C control of the fan is inadequate. The fan control is based upon the temp of the refrigerant, and that responds too slowly. In most cases, adding a relay and a diode will allow the fans to be triggered anytime that the A/C compressor is operating. This will improve the A/C performance and reduce the chances of overheating while it is in use.

You can use any standard heavy-duty 12 vdc single-pole, single-throw, constant-duty relay from the parts store. Pick up power from the jump start terminal, add a suitable in-line fuse at that connection. Ground goes to the chassis mounting point for the relay. Trigger it by tapping into the compressor clutch power wire. Output taps into the fan power line, with a diode to prevent feeding power back into the fan line.

Hold On

Sorry my Bad. Car is an 83S.

Yes the original A/C pusher fan is still out front. The Front fan is part two of the changes. What Wally is describing is exactly what I planned for the front fan. I want to take some of the load off that rediculous small relay in the HVAC head and have that fan turn on via same wires as A/C clutch.

Again, two seperate updated circuits. Less load on original electrics.

WallyP

You can use one relay or two relays - your choice. It should help a lot to extend the life of the HVAC head relay.

Hold On

Thanks guys, I will try and take some pics and document this weekend.