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Bad relay = cooling fan won’t come on

I picked up one of these. I've got the attachment with the disconnect that you unscrew so this will be on the back of the battery abd out of sight,

www.ebay.com

Battery Terminal - 3 post With Cover - High quality- Positive Side + | eBay

<p>3 post Battery Terminal Connector</p><br /><p>High Quality European Auto Stock </p><br /><p>Great for Adding Accessories. </p><br /><p>Nylon Lock Nuts on Posts</p><br /><p>Red Snap on Cover </p><br /><p>Any ?s please Ask -Honest Seller</p><br /><p>Free shipping in US</p>
www.ebay.com
 
I went to a local marine store and bought a fuse box for a boat with a clear splash cover that snaps on, a different type + cable end and added a #10 or #8 ? Wire to feed it then fed some extras off it
 
Andy69 said:
I picked up one of these. I've got the attachment with the disconnect that you unscrew so this will be on the back of the battery abd out of sight,

www.ebay.com

Battery Terminal - 3 post With Cover - High quality- Positive Side + | eBay

<p>3 post Battery Terminal Connector</p><br /><p>High Quality European Auto Stock </p><br /><p>Great for Adding Accessories. </p><br /><p>Nylon Lock Nuts on Posts</p><br /><p>Red Snap on Cover </p><br /><p>Any ?s please Ask -Honest Seller</p><br /><p>Free shipping in US</p>
www.ebay.com
Click to expand...
That looks pretty nice just fuse all leads off of it 🙂
 
Still can’t get it to work. Cleaned up the wiring and it looks great.

Fan works. Hooked directly to power it runs. Relay is tested good. Ground wire on the temp sensor is wired directly to the relay and has continuity. When I unplug the sensor the relay should trip and the fan come on but it doesn’t. If I ground the sensor terminal on the relay with a jumper the relay clicks.

Not sure what to check next.
 
I'm pretty sure it's the sensor in the intake that isn't grounding properly. The fan runs when I ground that terminal on the relay so either the ground isn't good or the sensor is bad. I just replaced it so it should be fine.
 
I did, but only on part of the threads. I left some at the bottom, but I have had the sensor out a few times so maybe there is some build up
 
I tested the ground between the sensor and the intake and it's good. I removed the temp sensor and tested it in a pot on the stove, it closes at 190 like it should and completes the circuit as verified with my tester.

So, the fan works when powered directly, the relay works when I manually ground the terminal that the temp sensor is wired to (the relay clicks and the fan comes on), the ground on the intake is good, there is continuity in the ground wire from the sensor to the relay, and the sensor appears to be working correctly.

What else could it possibly be?

The engine comes up to temp and the fan doesn't kick on.
 
If you're using the fan sensor on the t stat housing and the sensor (fan switch) is sitting in it,the sensor could be sitting in an air pocket and not getting hot enough to trip it to ground .Try switching your sensor to the cylinder head fitting on the drivers side cylinder head and see if that gets it to work.
With all the things you're going thru its worth the effort
 
My next step when it warms up is to test the ground on the switch while the car is running. About the only thing left is that the switch isnt getting Hot enough to open,

ive got the sensor for the dash in the head, not sure if there is another one.
 
There maybe a plug in the other side head but good luck getting that out. Unless you have an acetylene torch to heat the head up its almost impossible to get one out without one. You could remove the dash's switch temporarily to see if it works that shouldn't hurt anything.
Also there are relay adapters for diagnosing electrical problems. You remove the relay then put the jumper in the relays place then plug the relay into the relay jumper. It has a tab for each of the relays connections sticking out the side of the jumper so you can see what happens when you add 12V or apply a ground without removing or replacing the relay
Or you could just use it to see what the voltage level is at each side of the relay.
 
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I may have missed this but if it’s a 1 wire sensor once the engine is at the temp the sensor is supposed to turn the fan on use a 12 volt jumper wire and clip it to the sensor wire while it’s plugged into the sensor and see if the fan turns on, if it’s a 2 wire once at temp see if both wires show 12 volts, if one wire doesn’t put a Hot jumper wire to it and see if the fan comes on, PS IIRC mines a 2 wire but car isn’t here for me to look
 
Well ok, the switch isn’t opening While in the car.

Going to try a new switch. Also the connection between the plug and thr sensor is sketchy But it just may have been me trying to balance the tester over a running engine.

I could try swapping the temp switch and thr sensor in the head.
 
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Actually the switch should go in the closed position when the temp sensor reaches temp then open when the temp gets lower, Im guessing you do have 12 volts going to the sensor? and coming out when the temp is at set temp?
 
I ordered a new sensor, I’ll see if that works, if not I’ll order a 1/2” thread version and ditch the adapter. Thing is when I remove it, coolant spills out immediately so it doesn’t look like there is an air pocket
 
The other possibility is that the dash temp is not correct and is reading way high.
 
Replaced the temp switch AGAIN. Still doesn’t work. The temp switch is leaking around it because I didn’t use pipe tape, so I know there isn’t an air bubble.


Fuck it. I’m ordering a thermostat housing with a boss in it for the temp switch. If that doesn’t work I’m putting it in the back of the garage for a while.
 
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Dumb question, did you probe the sensor itself to make sure it has a solid ground? Can't see how it wouldn't work otherwise.
 
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