e fan conversion, where to mount swirch

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I have a 97 jeep wrangler, a 4 banger and gutless at highway speeds, and a good mod has been to take the mechanical fan out and install an electric.

My thought on it was to get another stat housing and drill and tap for a thermal switch, and run it to a relay.

Is a stat outlet housing a bad place for a thermal switch?
Most aftermarket kits have a probe that slips into the fins. I don't like that style, but does it have any advantages?

Thanks
 
Just install a Tee in the outgoing heater hose from the water outlet ( not the return side going to the water pump) and place your switch to measure temp. there. Easy peasy and accurate point of measurement. Plus can be installed on most any setup fairly easily. Many Rangers and older (mid 80s to early 2000's) Fords/Lincolns had a tee in the heater hose for this same kind of measurement for the ECM or the auto temp control measurement point in the years before networked modules could do the job with less duplicate sensors installed on the vehicle.

BurrWinder
 
The thermostatic switch should monitor the radiator temperature, not the thermostat housing.

You only need the fan to run when the coolant coming out of the radiator is too hot to sufficiently cool the engine. You want to have the switch mounted on the lower third of the radiator, preferably in direct contact with the coolant.
 
the outside radiator fin contact type are ok as long as they dont corrode and are adjustable.
 
Originally Posted By: djb
The thermostatic switch should monitor the radiator temperature, not the thermostat housing.

You only need the fan to run when the coolant coming out of the radiator is too hot to sufficiently cool the engine. You want to have the switch mounted on the lower third of the radiator, preferably in direct contact with the coolant.


Again.. putting in the coolant is probably the best if you don't want it ( on/against/make new holes in ) the radiator. Hence the setup I was proposing in my last post. The temp can usually be adjusted or a sensor chosen for a particular temp desired and installed in the location I described easily.

BurrWinder
 
If I were designing a sensor for a retrofit, I'd consider one that replaces the drain plug at the bottom of the radiator.

I wonder if such an animal exists? It would be at the bottom of the radiator. It should always be in coolant, and you wouldn't need to splice anything, just fit it where the drain plug is located.

What are the downsides to such a sensor placement?

Originally Posted By: djb
The thermostatic switch should monitor the radiator temperature, not the thermostat housing.

You only need the fan to run when the coolant coming out of the radiator is too hot to sufficiently cool the engine. You want to have the switch mounted on the lower third of the radiator, preferably in direct contact with the coolant.
 
Do you take it off road? I don't understand why, but the aftermarket electric fan kits never hold up off road. The 2.5 is a gutless wonder, though. Pretty reliable ... just no power. And decent crawling off road, too.

It does have to have a minimum temperature to be "happy" and get the best fuel economy and power.

The renix MPFI system that was used on the 2.5L back in the early YJ had two temperature sensors. Chrysler didn't do too many updates to the 2.5L ... there may actually be an extra port on the radiator to add an extra coolant temp sensor or thermo switch. I know on the XJ aftermarket radiators there is an extra port.
 
Do you have an engine lifting hook held in by two bolts? Unbolt one of them and stuff the sensor in there. I did this making a wrong-year saturn head fit and work with an extra sensor. It read "hot" by a little so it would conservatively cool. It doesn't tap to water so you can reverse it and put it somewhere else if you don't like it.
 
Originally Posted By: javacontour
If I were designing a sensor for a retrofit, I'd consider one that replaces the drain plug at the bottom of the radiator.

I wonder if such an animal exists? It would be at the bottom of the radiator. It should always be in coolant, and you wouldn't need to splice anything, just fit it where the drain plug is located.

What are the downsides to such a sensor placement?

Originally Posted By: djb
The thermostatic switch should monitor the radiator temperature, not the thermostat housing.

You only need the fan to run when the coolant coming out of the radiator is too hot to sufficiently cool the engine. You want to have the switch mounted on the lower third of the radiator, preferably in direct contact with the coolant.


Downsides are many...
Many (most it seems) modern radiators do not have drain plugs.
Not all of them are the same - or even removable (captive retainer in bottom of radiator drain hole )
Coldest part of the radiator - not in a good location for the flow of coolant.
Lower (closer to ground/front edge of vehicle) doesn't help for corrosion from salt water / moisture in operation.

BurrWinder
 
After I thought about it, I suspect some are like my old domestics with a petcock and not a drain plug.

Just no easy answers when you are trying to retrofit something to a car that wasn't designed to use it.
 
I have a flex-a-lite e fan in my hot rod. Wasn't crazy about poking the probe through my new aluminum radiator, but I did, and it works perfect. Just adjust to knob to come on at the temp you want. Probe is mounted near upper inlet hose. Comes on every time when it gets to it's set temp, and never overheats.
 
Originally Posted By: BurrWinder

Coldest part of the radiator - not in a good location for the flow of coolant.

BurrWinder


You actually WANT an electric fan sensor to be at the radiator outlet, not the inlet. The engine water outlet temperature is pretty constant, so the fan would be off until the engine actually OVERheats, then it would kick on. You want the fan to maintain a relatively constant temperature water feed INTO the engine, and only come on when natural air-flow isn't adequate. Every fan installation kit I've ever seen recommends either a sensor in the return hose, or as near the return tank as possible when inserted into the radiator fins.
 
I don't off road it much, washed out fire roads and a Buddy's field at best, but it would be awesome to push More than 70 mph. The 5 HP the fan sucks would go a long way towards that.
I'd like to find a place to drill and tap over a tee in the rad hose, but prefer that to an external probe.

Why do they put some coolant temp sensors in water outlets? I have seen more than a few, and that led me to think the outlet wouldn't be a bad place. I understand what you are saying 440magnum, but they seem to counteract each other

I intend to use a suitable OEM fan on the jeep. I used a pt cruiser on my grand Cherokee and it did a good job. Maybe source one of those or a Taurus fan
 
It would be really easy to solder another tapping into the bottom tank of a metal radiator. Plastic, not so much.
 
Originally Posted By: 440Magnum
Originally Posted By: BurrWinder

Coldest part of the radiator - not in a good location for the flow of coolant.

BurrWinder


You actually WANT an electric fan sensor to be at the radiator outlet, not the inlet. The engine water outlet temperature is pretty constant, so the fan would be off until the engine actually OVERheats, then it would kick on. You want the fan to maintain a relatively constant temperature water feed INTO the engine, and only come on when natural air-flow isn't adequate. Every fan installation kit I've ever seen recommends either a sensor in the return hose, or as near the return tank as possible when inserted into the radiator fins.

I installed mine according to the instructions, near the upper inlet. It really doesn't matter, just adjust to get it to turn one where you want it. 180+ on the temp gauge. 210 is the sweet spot.
 
What 440Magnum said. Cars with stock electric fans almost all work that way. When the coolant leaving the radiator reaches about 160 the fan turns on. The important part of this arrangement is that the engine and the coolant entering the radiator run steady at 190, they will not creep up before the fan turns on. The thermostat always has proper control of the engine temperature.
 
Originally Posted By: hansj3
I'd like to find a place to drill and tap over a tee in the rad hose, but prefer that to an external probe.


The water pump, right where the lower hose connects. As others have said you don't want the fan running the entire time the engine is up to temp (t-stat open), you want the fan running when the speed you're traveling isn't enough airflow through the radiator to cool the engine sufficiently. You could drill & tap, or clamp, or JB-Weld the thermocouple to the lower hose inlet on the water pump.

Or you could cut your lower hose and install a temp sender fitting like one of these: http://www.summitracing.com/search/part-type/temperature-sender-fittings

That is if you are super paranoid about using the method employed by thousands of e-fan converts and just sticking the probe through the fins. I happen to agree with you that there are probably more consistent and reliable temperature sources than a probe stuck through the fins; those are my ideas about how to kill some time and end up with (very likely) a "better" end result.
 
Originally Posted By: Traction
Originally Posted By: 440Magnum
Originally Posted By: BurrWinder

Coldest part of the radiator - not in a good location for the flow of coolant.

BurrWinder


You actually WANT an electric fan sensor to be at the radiator outlet, not the inlet. The engine water outlet temperature is pretty constant, so the fan would be off until the engine actually OVERheats, then it would kick on. You want the fan to maintain a relatively constant temperature water feed INTO the engine, and only come on when natural air-flow isn't adequate. Every fan installation kit I've ever seen recommends either a sensor in the return hose, or as near the return tank as possible when inserted into the radiator fins.

I installed mine according to the instructions, near the upper inlet. It really doesn't matter, just adjust to get it to turn one where you want it. 180+ on the temp gauge. 210 is the sweet spot.


Yes, this kind of talk is the most important... Adjustment for a certain application.. and flow of a radiator/system....

BurrWinder
 
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