Installing a switch for the cooling fan.

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  #1  
Old 06-21-06, 03:36 PM
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Installing a switch for the cooling fan.

After replacing the water pump, thermostat, relay, and cooland temp sensory, I have given up all hope of my 90 Grand Caravan's fan turning on by itself, so I think I will just install a switch, can anyone tell me how to go about this?
 
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  #2  
Old 06-21-06, 03:48 PM
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Well that depends on why the fans weren't going on.

You can wire it to turn the relay on or your can completely bypass the relay and use the switch. IF you by pass the relay you need a much bigger switch
 
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Old 06-21-06, 03:54 PM
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Before you start going nuts try a connecting the wires of the fan to the battery check and see if the fan even works.

Next, I hope you can understand how a relay works. depending on the number of pins of the relay if 4 pin 2 are used to power the fan if 5pin then 3 could. What you want to do is with a voltmeter or even test light see if 2 of the pins where the fan relay is are hot. Next look on the picture of the relay and see which pin numbers are to supply power to the fan jumper those out. This will verify if the wiring to the fan on the power side is ok. If this jumpering technique works then you will want to test the wires for powering the coil for ohmage and make sure they are very low like 1ohm give a take a few maybe even less. You may have a bad wire some where or a fan that straight up is broken.
 
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Old 06-21-06, 04:12 PM
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other wise get a high current switch and run a wire to the battery terminal and then to the switch and then from the switch to the wire on the fan that usually supplies power. You can use butt connectors to or what ever you desire to connect the wires
 
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Old 06-21-06, 06:24 PM
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Forgot to mention that I did replace the fan, from a new caravan in the junkyard, did the jump the relay test on both fans and they both worked, now one day when I opened the hood the listen to a noise the fan was running, drove it home and it hasnt worked since, any ideas before I start wiring? lol
 
  #6  
Old 06-21-06, 06:35 PM
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If you rewire it for a switch, please don't forget to make certain there is a fuse in the circuit.
 
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Old 06-21-06, 06:41 PM
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Fan working as designed?

I have to ask this, is the temperature getting higher than normal on hot days? The fan may not be designed to come on until the thermostat alone cannot keep the temp regulated. On my truck, I have a 195 thermostat, the fan does not come on until over 205 by the dash meter (it is a Dodge truck). It just makes sense that the fan only comes on if the primary source of temperature control is unable to control adequately.

Really, the only time the truck fan has come on is when it has been hot and I have been stuck in stop and go traffic, other than that, movement and the engine (mechanical) fan are sufficient to keep things cool.

What is it doing that makes you suspect the fan is not working properly?
 
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Old 06-21-06, 06:54 PM
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DavePearson does bring up a good point and begs the question: Is the vehicle overheating?? If not, then there may be no call for the fan to be running.
 
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Old 06-21-06, 07:26 PM
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Retest the fan 1st. You may have a blown fuse link. I've seen this before on a caravan due to the fan wire insulation getting burned from the exhaust manifold which then caused a short. The fuse link was too hard to get to so I spliced in a fuse holder from the battery cable.
 
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Old 06-21-06, 07:47 PM
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Try gounding the wire that goes to the temp switch.

I have a feeling you mayhave a bad wire in that part of the circuit
 
  #11  
Old 06-21-06, 08:41 PM
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Yes, it does overheat, and its overheating faster now that summer is here(having the heat on in 80 degree weather isnt fun lol). and the fan connecter is no longer there, I spliced the wires together as they connector wasnt the same since I got the fan from a newer caravan.

What is a fuse link and where would it be? o.o
wiring isnt something thats really easy to me so where would I start looking for that ground from the temp switch?
 
  #12  
Old 06-21-06, 10:21 PM
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A fuse link is basically a special small section of wire which is joined inline within a power wire that will melt inside to act like a fuse. The one I dealt with was too much a pain to access and replace. It was wrapped up in a bundle of wires right where they go into the firewall on the drivers side. Try the relay jump test again across the terminals that supply power directly to the fan. If the fan doesn't work, you have a bad fusible link, a bad connection at your splice, a broken wire, or a bad fan. Be sure you have no exposed wire or metal at your splice.
 
  #13  
Old 06-22-06, 02:19 AM
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Temp switch, testing relay, etc

My Dodge truck is newer than your Caravan (10 years), so there are (I am sure) some differences. But I did play with the fan ckt just to make sure it was going on for my own peace of mind. This is what I did.

I popped the relay, the control diagram is right on the side (it tells you what leads control the coil and what leads control the fan). The relay is controlled by the computer, so I could not check the system voltage on the + side, but I could verify the relay had a proper ground (measure resistance from the low side to ground).

Next, I measured the voltage on the terminal (hole in the relay jack) that was supposed to have the voltage to control the fan (on my model, it was the one in the center of the relay). The voltage should be battery voltage.

Make a jumper (preferrably fused, but I hate to admit it, I did not). The jumper I had consisted of a wire, and 2 pointed ends from speaker connections I had left over. I put one of the pointed ends in the relay slot that went to the fan, the other direct to the battery. The fan came on fine (I did not keep in running for more than a second or two just because the jumper was not real beefy).

I then took a 12V power supply (a 1 amp battery charger) and verified the relay worked by energizing the coil and verifying the relay closed (heard a click). As a note, if you have a relay with a diode installed, (funny arrow on the schematic in parallel with the coil), it will only work with the power hooked up in one direction.

If I did have a problem with the fan, it had to be between the computer and the relay (the sensor works because it is also the one the controls my temp meter).

As a disclaimer, if you do not know how this is wired/controlled, get a manual with the wiring diagram (so you can see what side of the fan the relay is on, whether the computer conrols the fan or there is a temp switch, etc). My Haynes had the ckt diagram for the fan ckt. Also, I would recommend doing this only if you are comfortable with electronic ckts. A shock can hurt and there is always the possibility you can kill other components if you make a mistake.
 
  #14  
Old 06-22-06, 02:53 AM
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the computer controls the fan so dont go grounding any temp sensors as it will not help to diagnose the problem and could possibly damage the computer.
suspect it has a burnt fusible link also,usually along the drivers inner fender or behind the washer bottle, the relay will have 2 power circuits that will be 12 volt positive one will be only with the key on the other will be full time battery voltage if you do not have 12 volts at any of the terminals with the key off then a fusible link is probably bad.
 
  #15  
Old 06-22-06, 08:22 AM
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There should be 2 temp sensors. One in the block and one in the radiator or thermostat housing, depending on his model and motor choice. The one in the block you don't ground. And if you ground the one for the ecu it will not damage it. Because the signal is picked up to the buffer after a series resistor. This way they can detect a failure mode such as an open or short to ground in the wiring safely.
 
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