Odd cooling fan (delay) question

[Rockfrog]

So over the years I've heard many a folk ask about having the efan remain on after the engine is shut down ...

 

Two ways I see it... The common way would be to run direct power from the battery (loop coil pos on the relay from batt pos). Then the thermo switch controls fan operation in all cases ... Until the battery dies. Not so good. This can be prevented with the addition of a manual control switch.

The other way is to source some form of timer, or complicated series of relays and doodads to accomplish the same task.

 

On that second solution I have a question ... Would the headlight dealy relay not work to accomplish the same thing? Allows full function for another 30 seconds post shutdown. A manual switch can be used to supply power before/after shutdown to simulate the headlight switches part in the circuit. Or possibly wire it in so it always runs in delay mode?

 

After having a considerable overheating incident whilst towing this weekend ... Mech fan clutch failed and the truck never had an efan. Swapped the mech clutch and all was good but that efan would have made the issue much less of an issue. Got hot enough to melt my intake piping under the hood. When I pulled into the campsite, she was just about in the red zone (stock Guage but this one seems to read fairly accurately).

Would there be any benefit to the delayed coming fan operation?

 

 

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[schardein]

I used to run dual electric fans on my CJ7 with a 4.0.  Wired the relays hot all the time, and used a temp switch I mounted in the water neck to trigger the relays.  The fans would stay on a minute or two after shutting down the engine, never enough to kill the battery.  

[yxmj]

I have a fan control set up that allows the fan to be turned on and off by a thermo switch that can be overridden by a manual switch that will keep it on or off as long as you like. I have never had an over heating problem with this set up. But to answer part of your question. the fan would not stay on until the battery dies. it would shut off once the temp near the switch reaches its active range......I would note that the engine itself would still be hotter than the area the fan is cooling as with no water flow the fan is just cooling the rad directly in front of it....you would get some residual effect on the block from the moving air.

 

Side note****I just drove a 92 2.5 YJ with the above set-up 5500 kms (about 3500 miles) from Manitoba to the west coast though the Rockies and 8 of the top 10 mountain passes in Canada. On my set up i put a LED on the dash that tells me when the thermo switch turns the fan on.....daytime temps were in the high 80's in some spots ....on my trip it only turned on twice....Both times in heavy traffic of big cities....never came on on the highway or even with day to day driving. This was only a one fan set up...with my 4.0 i have a second fan that is just manual no trigger switch.

 

On all I use a trigger switch out of a 90's vette that comes on at 210.

[Rockfrog]

Well, until I started towing, I only had the stock clutch fan, no efan at all. Never overheated, or over 210F in the last 5 or so years. Now that I'm towing ... The heat has risen, and without the efan it stayed there. The stock clock locked itself in the "cool" mode which also didn't help.

So what I have done now is wired up an efan using the old EGR solenoid 12+ (orange black lead) as the trigger for the relay. Then direct from the battery and grounded to the fender ground point.

Currently the efan comes on with the key (grounded the fan and relay together for now), it runs for a second as the system energizes with the fuel pump primer (since it runs on the same circuit). Sort of a system test as it were. Then runs all the time while the IGN is energized. For now I can pull the trigger lead (which will eventually be routed through a thermo switch - on order) and disable the system when not towing as it's not really needed.

I will say with just the replacement fan clutch Temps were reduced to a max of 210F (or roughly straight up).

Been driving around with it all energized the last two days and the usual slight cycling in traffic is gone, she warms up and stays at the thermostats 195F steady like a rock.

 

 

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