i am currently running a generic themostatic fan switch (probe type) w/ my electric fan, but i'm really not that thrilled about how well it works, particularly the on temp/off temp variations, and would like to replace it. i can get it to come on at the desired temp, but it really stays on too long, well after it should shut off. i think its just because its a cheap switch. i would prefer to stay with one of the probe type that attach to the radiator, just for a cleaner install. any suggestions as to a type you guys have had good luck with? i would be willing to explore the ones that mount into the head or manifold cooling passages if someone out there has had better experiences w/ that type. it does need to be a variable switch, though. i've looked into both perma cool and derale, both look like good pieces, but just would like to get some other opinions first. thanks in advance for any replies. graemlins/beers.gif

I have used the Durale (the soildstate unit) quite a few times with good results. Although most of the units I have delt with, I have installed a relay to just the fan for current isolation......I think it helps the circuit last longer by limiting the current through the device itself.

You can also build your own. Heres a link that has designs and part requirements/numbers for doing it:

http://www.geocities.com/smithmonte/Auto/MarkVIII_Fan.htm

Its about 2/3's down the page. Hope this helps! smile.gif

chicane, very cool information there graemlins/thumbsup.gif , i like the do it yourself version, if nothing else just because, well, you did it yourself. the derale kit did look fairly nice, and compact, which is nice. so are you saying you used the device to switch the relay, and used the relay n/o contacts to run the fan? also, where have you found to be the best place to position the probe, as far as location on the radiator? i would like to get this thing nailed down, it keeps the car running cool, but it just stays on way longer than it has too. i suppose i'm just bothered by nothing, since it doesn't draw down the battery or anything, it just seems unneccesary. i would be curious as to how you generally wire these up, circuit wise, i'm just running a t stat, no other manual switch, to constant batt. power, i figured there is no real need, as the fan would shut off when its cool. i am always open for suggestions, however. thanks again for all the info, it was very helpful! graemlins/beers.gif

To answer your questions, yes I did use the device to switch the relay. It isolates the larger current draw going to the fan and makes it eaiser on the fan-stat for a couple of reasons. First, some fans draw more current than others and using a relay helps protect the fan-stat from current loading beyond it rating. Secondly, its eaiser to wire a manual over-ride switch and cleans up the installation.

I normally mounted the fan-stat on the radiator core support, right behind the head light. It keeps it out of the way there.....

I will have to say the mounting of the probe should be closer to the radiator inlet. As you would normally mount a mechanical guage sender into the intake manifold, this would support a 'reading' of the temperature that would co-inside with any guages you are using.

As for wiring, use 'breaker's for the power leads on the fan-stat and relay themselves (30 amp). This will protect the entire system. The directions for the fan-stat are laid-out pretty well. You are only adding breakers to the 'hot' un-switched circuits and wiring a stat 'over-ride' switch, which basically just by-passes the fan-stat 'switched' signal to the relay and turn on the fan. Another thing would be to wire a 'free-wheeling' diode into the fan power leads themselves. The link I gave you shows you how and where to place them. This protect the circuit from the stored energy that the fan produces when not on and air is flowing through it from driving down the road.

thanks chicane. graemlins/thumbsup.gif yeah, the relay part is clear, i initially was reading more into it than was there, pretty much basic electronics. and do you feel its neccessary for the manual override switch? i didn't at the time, figuring if the t stat does its job, it wasn't needed. but i did consider a switch to disable the system, between the device and relay, so if you wanted you could shut the fan off. my switch/relay is mounted on the core support as well, this seemed to be the best spot. i also have the probe mounted against the inlet side tank, about halfway down the core, and i think i may put it closer to the actual inlet itself, as you described. i will likely s/c my current t stat anyway, and start out with a new solid state unit, it should be more consistent with on/off settings. i'm an electrician, so this type of stuff interests me anyway, and i like to see other peoples takes on how to do things as well. thanks again for your time and info graemlins/beers.gif

I would have to say that the main reason for a 'manual' over-ride is a back-up for if the fan-stat were to fail or become in-operable.....and if you were at the race track, you could turn the fan on and have it stay on in between rounds to further help dissapate heat.

good point. thanks again graemlins/beers.gif

Originally posted by chicane67:
I would have to say that the main reason for a 'manual' over-ride is a back-up for if the fan-stat were to fail or become in-operable.....and if you were at the race track, you could turn the fan on and have it stay on in between rounds to further help dissapate heat. On my project cars (Cobras, Grand Sport, etc.) I set the fan up through a relay with a thermostatic switch, and add a double-pole double-throw toggle switch at the cluster as a manual override so I can turn it off if necessary or turn it on if the thermo switch fails. I also add a yellow LED in the cluster so I can tell when it's operating. graemlins/thumbsup.gif

john, i do like that idea. graemlins/thumbsup.gif have you guys found a good source for 12v toggle switches, and other 12v electronics? i would like to find a d/p, d/t toggle that is fairly small and discreet, unlike the big clunky plastic ones all the parts stores seem to have. i was considering mounting it on my gauge pod, and don't wan't it to stand out like a sore thumb. then maybe put a small led next to it. thanks for all the good input you guys, thats exactly what i was looking for! graemlins/beers.gif

Radio Shack has lots of them, in many styles; I only use them to control relays, not direct high-current switching. graemlins/thumbsup.gif

For electronic parts in general, I like digi-key. They have reasonable order policies and good delivery times. Just watch the current ratings on the switches. You can get some pretty cute switches that won't stand up to the task. By using a relay, you'll almost never have a problem.

http://www.digikey.com/

-dnult

alright! thanks a lot you guys. i'm back to busy with work so now i'll have to find time for the camaro (i know, my priorities are all screwed up ;) ) but i will definately look into those places. i'm sure i can find what i have in mind, at one of them. and as you said dnult, i'll be using relays so my choices should be a bit better, not needing a huge amp rating. i really do appreciate all you guys' help, hope i can return the favor graemlins/thumbsup.gif graemlins/beers.gif