I have access to a rad and dual electric fans out of an 88 honda prelude.... I know I could hard wire them in to run all the time, but would prefer to have it set up like it is on the prelude.... After I would shut my prelude off, if it was warm, the fan would stay on for awhile and cool the engine I guess, until it reached a certain temp, since that apparently is when enigines will heat up the most, because of lack of air movement, anybody have any thoughts or ideas on that?? How do I go about setting that up?? And is it safe to run these fans??

 

THermostat, powered off the battery directly (not through internal wiring), perhaps w/ a cutoff below a certain temp.

 

but how do you get a connection between the thermostat, and the fan??

 

By thermostat he means an electric one made to use with electric fans, not the thermostat that controls coolant flow. I'm sure you could get one pretty easily and wire it up to run based on coolant temp.

 

but how do you get a connection between the thermostat, and the fan??


use a relay.

the thermoswitch is open at low temperature and shuts at a specific temperature, it stays shut until the temperature drops below the switch set point, when it opens again.

I have seen two basic types of thermo switches.

1] one wire, the switch grounds the wire through the switch body to whatever metal engine bit it is screwed into.

2] two wire, it connects one wire to the other wire.

2a] three wire, like VWs use. a two temperature switch, connects one wire to another at a set temperature, at a higher temperature it connects the other wire to the others.

if the honda switch screws into the plastic radiator tank it probably is a two wire type.


to use it to run the fans I would run one wire to the ground of the relay and the other wire to a body ground.

I would run the switch hot wire of the relay to a fused always hot, like the battery positive.

the switched side of the relay would have one wire run to the same battery fuse, the other side of the relay switched would go to the fans.
the fans would then have their ground wires hooked to ground.

this way the fans would be off until the temperature switch closed, which would ground the relay which would turn on power to the fans.

the fans would then run until the temperature of the thermo switch dropped to its opening point.
with the car turned off.

the main thing about this seems to be where you mount the thermoswitch, if you mount it where the temperature will drop instantly the fans will shut off before they do any good for the engine.
if you mount it where the heat takes a real long time to cool down, the fans will run too long wasting battery power, possibly draining it if you do lots of short trips with lots of fan running between them.

 

Having the fans run while the engine's off will do jack **** because the coolant's not circulating.

 

on the other hand the fans would be circulating cooler air over the hot stuff that is not cooled by water circulation, like the exaust pipe, alternator and suchlike.

keep in mind that the radiator is NOT as laid down as in the later models, making thermal convection more likely to be useful.

what IS the relationship of the top of the radiator to the waterpump ?

 

you need something like this. thats what im buying when my turbo FB is done except the fan shroud will also cover the oil-cooler below the radiator.

 

Well, I have the fans installed now. I really don't know if it was worth the effort or not yet. Currently I just have the fans wired to a switch until I can figure out how to wire in a thermostat of somekind. Thanks for the help, any further suggestions would be helpfull.