Hot Rod Forum banner

fan control. keep running after engine stoppped

3K views 23 replies 8 participants last post by  EOD Guy 
#1 ·
I could not find anything in "search" on this question. I want my fan to keep running after i turn the kar off ..at least drop from 180 down to 160 degrees, what is the easiest way. [kars all finished years ago]to accomplish this? It has a regular hottronics shut off sender, in the head It works good, but watching the temp gauge climb after the kars off gets me worried. Can you give me any info on this how,to get this thing working as i stated thanks for any help bob s

sorry!!:( i can't usually find stuff on search
 
#2 ·
I used Dakota Digital's fan controller, It will let you set any temp (On or Off) Controls up to 2 fans, You can select how long the fan stays on after ing off and has a trouble shooting mode that allows you test run your fans with out warming up the eng.

Kinda pricey tho, best money I ever spent.
 
#5 ·
fix for fan

I belive you can get what you want at no cost. The relay you're currently using has to have a 12 volt power source from somewhere, which is most likely a switched source from your ignition. If you simply change that to a battery hot source the fan should continue to run until the temp sensing device tells the relay to shut the fan off. The relay won't know the engine is not running.
 
#6 ·
why

While bob70 is correct in that the controls need to be connected to a HOT-ALL-TIMES source so the fan is controlled even after the Ignition is OFF there is really no reason to run the fan after the engine is shut down.
After the engine is off the water pump is no longer circulating coolant through the radiator so the engine is not cooled any faster if the fan continues to run.
The temperature sensor will respond to the gradual decrease in engine temperature and eventually shut down the fan but running the fan will not affect this cooldown.

vicrod
 
#18 · (Edited)
After the engine is off the water pump is no longer circulating coolant through the radiator so the engine is not cooled any faster if the fan continues to run.
The temperature sensor will respond to the gradual decrease in engine temperature and eventually shut down the fan but running the fan will not affect this cooldown.

vicrod

The fan will push/pull loads of ambient air into that engine bay which will cool it down faster than a car that is just sitting with no help. Some cars come with this programmed into the factory tune. My old accord has a fan timer relay from the factory that I've only noticed come on a handful of times. Usually after a long traffic filled drive on a very hot day. Though I don't understand the desire to bring temps down from 180, that's low to begin with. The LS6 in my Cadillac is so crammed into the engine bay that it holds heat like no car I've ever seen. I can get in it several hours after shutting down and my oil and coolant temps are starting off in the 130 range. Full warm up takes no time at all, this saves engine wear, fuel, and adds to the fun factor because I can be going wide open throttle in no time.
 
#7 ·
Just to add..... the DD controller is plug and play, easy set up.

Running the fan while off, relying on a temp sensor to shut them down..... IMO is not the best way to do it...... cause if the temp sensor takes 45 min to cool dwn enough to shut off the fans....... you might be stuck with a dead battery.

Much better is to run on a timed circuit, on eng shut down my fans run for 1 min, then they are off.

When I made a prototype for the timed even etc.... parts (temp sensor, timer board, relays wiring) cost as much as the DD system, so I went with them.
 
#8 ·
fan switch

I genuinely appreciate what you guys are sharing with me.It sounds like i should most likely open the hood and let the heat out that way [quicker]..Although Vicrods suggestion makes me think,this maybe the best way for my situation.I am not concerned to much with the engine getting cooled down quicker. the fan would kool the radiator down abit thats a + ...but i still would have the really "HOT" hood, and the filler, next to the peaking strip down the center of my hood, [brake line tubing welded on]. won't start popping anytime soon. thanks for all the very experienced help.:thumbup: bob s
 
#9 ·
time delay

I see what you are saying. The fan keeps the air moving and helps cool the hood etc. after shutdown.
Per EOD guy the time delay would help this. The time delay relay (TDR) can be adjusted to any time that would help - say 10 minutes.
The TDR would start the delay after the ignition is turned OFF. The contacts of the TDR would control the fan power relay.
Check out Home - FactoryMation
The ELKO model #CRM61 is a universal TDR that could be used for this application. Cost is under $40 last time I checked.
This can be added to the controls you already have.

vicrod
 
#10 ·
I see what you are saying. The fan keeps the air moving and helps cool the hood etc. after shutdown.
Per EOD guy the time delay would help this. The time delay relay (TDR) can be adjusted to any time that would help - say 10 minutes.
The TDR would start the delay after the ignition is turned OFF. The contacts of the TDR would control the fan power relay.
Check out Home - FactoryMation
The ELKO model #CRM61 is a universal TDR that could be used for this application. Cost is under $40 last time I checked.
This can be added to the controls you already have.

vicrod
I tied your recc; i couldn't bring anything up... bob s
 
#14 ·
Some one mentioned "time delay". A National Semiconductor 555 timer would work very well as a time delay circuit. It's period and duty cycle are controlled by a RC combination. You could easily couple the output to a relay, bi-polar transistor or FET which in turn controls the fan. All that is needed is a little electronics knowledge.
 
#16 ·
You can buy 555 chip any where, Radio Shack etc......... However if you don't have electronics background, it will be diff to make the circuit, there are lots of bits that are needed for the circuit...... and those bits add up etc...... if you want to go that route it would be much easier for you to purchase a house alarm timer board and use the time delay of the board to control the fan relay etc...... Even that isn't plug and play......and the bits add up.
 
#19 ·
One this to keep in mind is that some of the electric fans can draw as much as 20 AMPS when running. If you leave the fan running to long you may come back to a dead battery. Before the fan can move any cool air it will need to cool the radiator first. GM and a couple other manufacturers did this for a while in the early 80's and gave up on it. Too many dead batteries. If you want to do this I would also try to find something that will shut down if battery voltage drops below 11.5.
 
#22 ·
Radio Shack has several different sizes of project boxes that could be used as an enclosure.
One more thing. Time delay relays used for OFF delay will require 12vdc at all times to maintain power to the timer circuit. This adds a very small load to the battery that should be considered.

vicrod
 
#23 ·
My Toyota MR2 has an engine compartment cooling fan. It doesn't work with the engine off, but it could be wired to. It is a smaller fan than the radiator fan and pulls a lot less current. There is a vent on the side of the car for hot air exhaust. If you mounted a small fan under the hood, it would probably do a better job of bringing the air temp down than one that is pulling air through a hot radiator.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top