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RENIX lower rad electric fan switch

M

mattbred

NAXJA Forum User
Location
Canada
The lower rad electric fan switch is buggered on my '89, so I bought a new one and tested it out in a pan of boiling water. Works perfect, right in unison with my new thermostat. Only problem is, it's located on the bottomish of the rad, right at the output.

Is this a design flaw? Wouldn't the water be effectively "cold" by the time it gets to the sensor? This would make it think that the jeep is actually colder than it is, delaying the startup of the fan, right?
 
mattbred said:
The lower rad electric fan switch is buggered on my '89, so I bought a new one and tested it out in a pan of boiling water. Works perfect, right in unison with my new thermostat. Only problem is, it's located on the bottomish of the rad, right at the output.

Is this a design flaw? Wouldn't the water be effectively "cold" by the time it gets to the sensor? This would make it think that the jeep is actually colder than it is, delaying the startup of the fan, right?
Click to expand...
The water would not be cold , it would be not as hot . The water at the bottom of the rad is going back in to the motor .
 
REPOXP777 said:
The water would not be cold , it would be not as hot . The water at the bottom of the rad is going back in to the motor .
Click to expand...

I know it wouldn't be cold cold, but it would be colder than the temperature gauge sensor's reading.

I guess the only way is to put it in and see what happens.
 
Yea that side of the radiator is cooler.The factory renix fan doesn't come on untill 220* but the renix switch opens at 210*.They should've put the fan switch on the hot side of the radiator IMO....if they did that the fan would come on at 210*
 
Well I finally installed my taurus fan, and my original electric fan together and when I short out the connecter that plugs into the lower rad electric switch, they both turn on no problem.

So I plugged the connector into the temp switch, and went for a drive. On the highway the temperature was perfect, but as soon as I did some burnouts in a dirt patch, my temperature soon rose to the red line and the fans never turned on.

Keep in mind I have tested the switch in boiling water and it worked fine. Is there a way to relocate the switch somewhere else? It's a very big flaw.
 
mattbred said:
Well I finally installed my taurus fan, and my original electric fan together and when I short out the connecter that plugs into the lower rad electric switch, they both turn on no problem.

So I plugged the connector into the temp switch, and went for a drive. On the highway the temperature was perfect, but as soon as I did some burnouts in a dirt patch, my temperature soon rose to the red line and the fans never turned on.

Keep in mind I have tested the switch in boiling water and it worked fine. Is there a way to relocate the switch somewhere else? It's a very big flaw.
Click to expand...

Are you sure that your wiring and relays are up to snuff? If they arent, and you run it for more then say 20 minutes, the relays / wiring will get too hot and cease to function.

Should be using nothing smaller then 10 awg for power. A standard 30 (preferably a 40) amp relay will work for low speed, but you want at least a 75 amp for the high speed.
 
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It sounds to me like your engine is getting hot, but not the radiator. A stuck thermostat, loose drive belt (not turning the water pump), cavitating water pump, or obstruction could all be to blame. When the engine gets hot after burnouts, touch the upper radiator hose and see if it is hot.
 
Muad'Dib said:
Are you sure that your wiring and relays are up to snuff? If they arent, and you run it for more then say 20 minutes, the relays / wiring will get too hot and cease to function.

Should be using nothing smaller then 10 awg for power. A standard 30 (preferably a 40) amp relay will work for low speed, but you want at least a 75 amp for the high speed.
Click to expand...

10 gauge to and fro the fan, to a 40 amp circuit breaker, to a 30 amp relay (all they had) on the LOW setting only. High is cut off. I've done my research, like I said both fans work when I short out the switch, its just that the switch isn't "switching".

It sounds to me like your engine is getting hot, but not the radiator. A stuck thermostat, loose drive belt (not turning the water pump), cavitating water pump, or obstruction could all be to blame. When the engine gets hot after burnouts, touch the upper radiator hose and see if it is hot.
Click to expand...

It does sound like that doesn't it? But when I'm driving at highway speeds, or hell even at 60 KPH, it cools right down to it's normal operating temp (right under 100 celsius).

I just replayed the thermostat and drive belt, and it seems tight.

It did cool down when I got up to 60 kph after the burnouts.
 
You have power to the switch right? Did it pop the fuse?
Click to expand...
If you read post #5, he explains that if he bypasses the radiator switch everything works, so no fuses, wiring, etc are to blame. He also says that the switch works when boiling it, so it's not the switch, so it must be the conditions in which the switch is exposed to, or a bad connection between the switch and connector.
 
outlander said:
Yea that side of the radiator is cooler.The factory renix fan doesn't come on untill 220* but the renix switch opens at 210*.They should've put the fan switch on the hot side of the radiator IMO....if they did that the fan would come on at 210*
Click to expand...

That is not correct, the Renix fan switch comes on at 170 F. The engine coolant temperature sensor and gauge may be reading anywhere from 190 to 230 F depending on various other factors but a properly working Renix electric fan thermoswitch turns on at about 180 F (+/- 1 F) and back off at 170 F (+/- 1 F). I have tested them.
 
88 Wagonman said:
If you read post #5, he explains that if he bypasses the radiator switch everything works, so no fuses, wiring, etc are to blame. He also says that the switch works when boiling it, so it's not the switch, so it must be the conditions in which the switch is exposed to, or a bad connection between the switch and connector.
Click to expand...

Now I see the problem!! The switch is BAD!!! A properly working Renix Thermofan switch in the radiator turns on at 180 F and off at 170 F!!!!! Not on at boiling which is 212 F at STP.

Matbreed you have a bad switch guy!!!!!
 
Ecomike said:
Now I see the problem!! The switch is BAD!!! A properly working Renix Thermofan switch in the radiator turns on at 180 F and off at 170 F!!!!! Not on at boiling which is 212 F at STP.

Matbreed you have a bad switch guy!!!!!
Click to expand...

Well, the stock one didn't come on ever, and the one I replaced it with (aftermarket) doesn't come on either.

However, I beleive it would work right if I moved it to an accurate place. Is there somewhere I can drill and tap in the hot side of the rad to fit the plug in?
 
why not use a thermostat housing from a year that has the threaded hole for the temp switch.

or drill and tap a hole in the renix thermostat housing for the temp switch.
 
Use the '92 up thermo hosing with the switch that's probably on it from the salvage yard. Get the wire plug and as much of the lead as possible. Splice the wire lead into the existing lower rad switch wiring and cover with split conduit.

Now the new location will read hot coolant direct from the engine and turn the fans on earlier, just like the the factory improved on '92 up. Works on mine when I did the closed to open conversion. There is somewhere a post on what yearmakemodel temp sensor will screw in that trips at lower temps, like 175*, out of some buick or other. Still looking for it.

Half of hot rodding is just making later factory stuff backward compatible.
 
mattbred said:
Well, the stock one didn't come on ever, and the one I replaced it with (aftermarket) doesn't come on either.

However, I beleive it would work right if I moved it to an accurate place. Is there somewhere I can drill and tap in the hot side of the rad to fit the plug in?
Click to expand...

First off, once again, a Renix thermo switch should be on at 180 F and off at 170 F, and cycle between 170 and 180 F. If it takes 212 F (you did test it in tap water, not atifreeze mix, right?) to turn it on, it is DEFECTIVE. Take it back and get one that works right. I bought mine at either autozone, advance or O'Reilys, I forget which. The radiator should be droping the 210 F engine outlet temperature to about 170 to 180 F in a properly working OEM jeep system. The water needs to be cold enough on the return side of the engine to remove heat from the engine.

Is this a new radiator? If not, the switch could be sitting in a cold dead spot of the radiator and thus the radiator is the problem?????

Try to isolate and fix the OEM part problem before you redesign it.
 
Replace the thermostat housing with a 1991-up? Good idea.

Drill & tap the OEM one? Bad idea. I don't recall that it has enough material to get away with that, and it's cast metal (not wrought.) So, you'll have a hard time drilling a clean hole and brazing in a fitting.
 
Ecomike said:
First off, once again, a Renix thermo switch should be on at 180 F and off at 170 F, and cycle between 170 and 180 F. If it takes 212 F (you did test it in tap water, not atifreeze mix, right?) to turn it on, it is DEFECTIVE. Take it back and get one that works right. I bought mine at either autozone, advance or O'Reilys, I forget which. The radiator should be droping the 210 F engine outlet temperature to about 170 to 180 F in a properly working OEM jeep system. The water needs to be cold enough on the return side of the engine to remove heat from the engine.

Is this a new radiator? If not, the switch could be sitting in a cold dead spot of the radiator and thus the radiator is the problem?????

Try to isolate and fix the OEM part problem before you redesign it.
Click to expand...
hmm, I don't know for sure when it did buzz in the pot actually. It might have been before it boiled. I wish I had a temperature gun/gauge with me for it. All I know is that the switch should have come on when my temperature was in the red zone. I don't believe the parts store will take it back, as it probably doesn't have a warranty? And I purchased it last fall and only just got around to putting it in.

The rad is a few years old, according to the PO. I don't think it's a dead spot as when I took the old switch out, a shit ton of coolant poured out (I hadn't drained it earlier).

Could be a bad connection, I'm going to test it with a multimeter and see if it works.
 
Ok I tested the switch with a multimeter, and the gauge went almost to the red and it still didn't complete the circuit.

So either the switch is defective, or the rad isn't flowing hot water at that location, or my main temperature gauge sender is showing a temperature that's WAY colder than it really is; something I doubt.

On the plus side, when I jump the fans so they run, it cools it down almost instantly.

It's just weird that the switch worked in a pot of boiling water, yet won't work in the radiator.. What to do? Drill and tap the rad right beside the upper hose?
 
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