Convert mechanical fan to electrical. Questions?

Hi folks,

The project at hand is to convert a 1984 XJ with a mechanical radiator fan, to an electrical one, or to be more precise, to a set of two electrical ones. The cost of the electrical fans is not big, about 120 US$, everything included.

I have a couple of questions though:

1. Obviously, one of the reasons I do that, is to eliminate the parasitic loss caused by the mechanical fan. My engine is not powerfull, so every pony I win, is a good pony. However, I am not sure what I have to remove. If I remember correctly, there are four which secure the fan clutch on the water pump. Do I loosen them and remove the fan/clutch assembly and then reinstall the nuts?

2. My XJ is equipped with air condition, but has no auxilliary fan, to cool the condenser. What I was thinking, is to wire one of the two fans to work whenever the air con is switched on. Do you think this is a good idea? As it is now, if the truck was sitting in the sun for a long time, and I started and turn on the air con, quite a few minutes pass before I get cold air out of it. Would the fan help in this department?

3. The two fans will be controlled by a temperature sensor, which is mounted in the radiator (that's what the shop told me). Any ideas where in the radiator the sensor should be mounted (up, down)? Also, if one of the fans is to be switched on whenever the air con is switched on, I assume that I will need a couple of diodes to prevent the current from flowing the wrong way. Any one can suggest what type of diodes I should use? Obviously, both the temp sensor and the air con with control the switches via a relay.

4. Finally, what do you suggest? The fans in front or behind the radiator? Pushing or sucking air?

Thanks and regards
---------

John SV1CEC

Which engine? My 4.0 doesn't have the fan on the waterpump, its on its own pulley. I put in a zirgo 2700 CFM 16" fan with a custom built shroud. Mounted behind as a puller. Cools wonderfully, but it is wired in with the other aux fan. Do you not have the auxillary fan?

John has a 4-cyl.

The factory mounts the auxiliary fan switch in the tank with the return hose coming from it. That's on the 4.0L with the horizontal-flow radiator. Does your radiator have the tanks on the sides, or at the top and the bottom?

I can provide wiring diagrams from a 1988. Let me know if you want them. The electrical manual includes both 4-cyl and 6-cyl.

Hate to say it, but unless you are coming up with something really exotic, it will not work as well as a "GOOD" stock set-up. Many people have tried, but most usually go back, cause it is better.

Good luck

james
www.geocities.com/jammerjamesharmon

actually, mine works better than the clutch fan

I don't know how many posts exactly like yours I had to pay less attention too, but I'm glad I did

DeftwillP said:

actually, mine works better than the clutch fan

I don't know how many posts exactly like yours I had to pay less attention too, but I'm glad I did

Click to expand...

You are in a definite minority. If John had a 4.0L I would have warned him not to try this. However, his problem isn't that he needs more cooling, it's that he wants more horsepower. I'm hoping that 2 electric fans will be adequate for the 2.5L engine.

You might also want to read from this link.
HTH
Dan.

Folks,

As Eagle pointed out, my XJ has the 4-cyl. 2.5 lt engine. And again, like he said, I do not have an over-heating problem, thank God.

What I am trying to do here, is to save a couple of bhp, from the engine's anemic output and put them to better use. The thought occured to me, as I was changing the horns of the Cherokee the other day (they went out, after the celebrations of the European Football (Soccer) championship we won).

Just in front of my radiator and condenser, there is ample of space. Enough to fit two electric fans. So, that gave me the thought of two pushing fans, that could replace the mechanical one and save me a couple of bhp.

That same day, I got in the truck to drive somewhere, it was early afternoon about 5 pm which for Greece is a rather hot time in the day, and the truck was sitting in the sun all day. It took the air con several minutes to start cooling the cabin. So the thought occured again, that maybe a fan would help the aircon bring out cool air sooner (am I correct on that?).

Eagle said:

The factory mounts the auxiliary fan switch in the tank with the return hose coming from it. That's on the 4.0L with the horizontal-flow radiator. Does your radiator have the tanks on the sides, or at the top and the bottom?

I can provide wiring diagrams from a 1988. Let me know if you want them.

Click to expand...

Eagle, my radiator has the tanks top and bottom. What I do not understand, is what hose are you talking about? The shop told me that the sensor is an electric sensor, only two wires will have to go to it. So I guess, if I'll take the XJ to the radiator shop which build my radiator, they would weld some threaded part on it, in which the sensor will be attached with power going to it and coming out of it to the fans relay.

And yes, I would like the wiring diagrams. Could you scan and e-mail them?

Thanks for your impute gentlemen.

Keep the ideas coming.

P.S. : Eagle, how about your PC? Was it infected? You didn't answer my e-mail.

SV1CEC said:

Eagle, my radiator has the tanks top and bottom. What I do not understand, is what hose are you talking about? The shop told me that the sensor is an electric sensor, only two wires will have to go to it. So I guess, if I'll take the XJ to the radiator shop which build my radiator, they would weld some threaded part on it, in which the sensor will be attached with power going to it and coming out of it to the fans relay.

Click to expand...

With a vertical flow radiator, the top tank has the pressure hose and the lower tank has the suction hose. With a cross flow radiator like the 4.0L engines use it isn't always obvious which is which. The switch doesn't go in the hose (although there used to be an add-on switch that did, but it's no longer available). I referred to the hose to identify which tank has the bung for the fan switch.

Didn't see the e-mail. I'll check later.

Eagle said:

With a vertical flow radiator, the top tank has the pressure hose and the lower tank has the suction hose. With a cross flow radiator like the 4.0L engines use it isn't always obvious which is which. The switch doesn't go in the hose (although there used to be an add-on switch that did, but it's no longer available). I referred to the hose to identify which tank has the bung for the fan switch.

Didn't see the e-mail. I'll check later.

Click to expand...

So the temp sensor should go in the bottom tank in my case, right?

Tnx

TRNDRVR said:

You might also want to read from this link.
HTH
Dan.

Click to expand...

I wonder what cfm those fans he was using are rated at. If the electric fan doesn't pull enough cfm that will cause it not to work as efficiently. Anyone ever thought of installing one or two pusher fans behind the grill to run while on a trail? I saw a pic of a guy that had a dual fan setup behind the grill but can't remember who/where it was.

-Mike

For another point of view, take a look here:

http://www.go.jeep-xj.info/HowtoElectricFan.htm