55.2-59 Electric Fan to Manuel Fan

[MALIBLOC]

I have a dual electric fan
I just took my thermostat out and drilled two small holes in the stat and put it back in
When I was driving today my fans would not turn on and my truck got up to 220, thermostat is a 160, the intake manifold is where the sensor is, Im not sure why the fans are not coming on, I looked for a fuse today but could not find one, Im assuming power is not getting to fan somehow, cause Ive never had a issue like this and I know the thermostat has nothing to do with electrical. Maybe underneath i may have kicked or disconnect the power somehow.
As a side note I drilled out stat last week and the truck and fans have been running just fine till today.

Question , can I bypass a fan relay and make the fan work with a on/off switch and get it to manuel somehow, Im sure its a easy fix???

[mongocanfly]

it would take a very heavy duty switch to use in place of a relay..lots of amp draw there
there should be a fuse somewhere ..
check to make sure your signal wire to the relay has 12v..
also make sure you ground is good...
what do you have that controls your fans?
I assume with the dual fans that you have a relay on each fan...

[burnin oil]

Temporarily run a hot lead from the battery to the relay and hook it to the terminal that the sensor was on. That should kick the relay and start the fans. If that works then you can replace the wire with a manual switch for the fans. This is the low amp side so any old switch should work.

With the switch in the intake manifold it may not be making good contact with anyifreeze. With the motor at or above radiator level it could have an air bubble in the system and the sensor is reading that air space and not coolant temps until the bubble gets purged. Try parking on an angle with the nose uphill once the temps are up for a few minutes and rev the motor up to around 2000 rpm. May get the bubble out.

[MALIBLOC]

Originally Posted by mongocanfly

it would take a very heavy duty switch to use in place of a relay..lots of amp draw there
there should be a fuse somewhere ..
check to make sure your signal wire to the relay has 12v..
also make sure you ground is good...
what do you have that controls your fans?
I assume with the dual fans that you have a relay on each fan...

Im sorry its a single fan not sure why I typed duals (long hot day)
basic set up its all automatic
fan to relay to bus block to battery
relay to sensor.

Im going to check the power source first and go from there

[MALIBLOC]

Originally Posted by burnin oil

Temporarily run a hot lead from the battery to the relay and hook it to the terminal that the sensor was on. That should kick the relay and start the fans. If that works then you can replace the wire with a manual switch for the fans. This is the low amp side so any old switch should work.

With the switch in the intake manifold it may not be making good contact with anyifreeze. With the motor at or above radiator level it could have an air bubble in the system and the sensor is reading that air space and not coolant temps until the bubble gets purged. Try parking on an angle with the nose uphill once the temps are up for a few minutes and rev the motor up to around 2000 rpm. May get the bubble out.

could possible be just this , I will try this , could I remove the cap and just run the motor for a bit too, since the system is not pressurized would that force any air out ?
I drilled the hole as a safety measure , my truck would get to 220 then jump down to 170, I removed the thermostats and placed it in boiling water to make sure it still worked and it did, but I drilled the two small hole, maybe a 16th each. Every since I did this my engine runs right at 170 like before but yesterday the fan would not engage.
Thanks for all your help guys , this is why we like old truck right!

[joedoh]

and just how does manuel feel about being installed under your hood to turn your fan on and off?

sorry, poor humor, not helping.


what WILL help is telling you that you can easily add a small switch to the trigger lead of your relay. find the pin that goes to your temp switch, it will be a small gauge wire on pin 85 or 86 (it could be either). verify that it is ground triggered by looking at the temp switch, the switch will be probably grounded in the block and have a single wire coming from it. if it has two wires it might be 12v+ triggered so I will discuss that in a minute.


assuming ground trigger, wire a small switch with one wire going to ground and the other wire tapped into this wire on the relay. done. now when you turn the switch on it thinks the temp switch is triggering the relay and the fan turns on.

if you have a 12v+ triggered fan, everything is the same except the wire to the switch will need to be a fused 12v+.

do NOT use the heavy gauge wire that runs directly to the fan, that will be pin 87 or 30 on your relay. neither of those!

I recommend using a momentary push switch you have to hold down, because it will force you to fix the problem by having you hold the button as long as its needed instead of turning on a switch and forgetting it

[MALIBLOC]

Another thing is the radiator was gurgling quite a bit, so Im assuming theres air in there . It seems like recently the radiator gurgles into the over flow and them when it cools down it seeps back into radiator, I may just top off everything and see if that solves this issue

[joedoh]

could be, if your temp gauge was spiking 220 it could be seeing steam at the sensor and giving a false high reading that isnt whats actually the water temp

[jwhotrod]

your radiator pushing fluid into the puke tank hot is doing what it should, allowing the expansion of the fluid getting hot a place to go. that is to get all the air out of the system and keep it out. If the radiator is transfering ok into the overflow tank and not puking out onto the ground dont refill it. once the system finds its level it does not need to be constantly topped off. the system in my 35 chevy has not been touched other than to check the level in the puke tank hot a couple of times, in over a year. Same as a new car.

[mr48chev]

Original style radiator or cross flow?

Original style radiators have to have room left for expansion in the top tank. As Jwhotrod said, they tend to seek their own level.

I've see a guy have problems running a cross flow where the top of the radiator and the fill neck was actually below the top of the thermostat housing. Air got trapped in the engine and never did burp out until we installed an inline filler and radiator cap in the hose at the high point . That was A Chevy V8 in some sporty car it didn't belong in though.

[burnin oil]

This. The whole idea for getting the nose high is to get the air bubble to move. I have worked on a few vehicles that squishing the radiator in your hand did the trick also.

The idea behind drilling the thermostat is to let the coolant bypass it when cold and even out the cycling when hot.

If you have access to a heat gun I would verify the gauge readings. 220 degrees is pretty hot and lends to the air pocket theory and the sender seeing steam temp instead of coolant. If the temps are actually that hot after forcing the fan on there is probably something else going on.

Good call to the guy saying the sending unit is probably a switched ground. This is common on electronics and can work fine on a relay. I am used to relays being hot side switched, technically positive side switched.

[MALIBLOC]

So no issue before I drilled out thermostat, and when I drain out radiator and refilled I just filled it and went cruising, and it was ok during my first cruise which was about 40 miles but the second cruise about two hours later and the abeyant temperature outside was about 20 degrees hotter , thats when the temp went up and no fan switched on .
Today I had time so I opened up the radiator cap and the water level was down significantly and the overflow tank had about 12 fl oz (not alot)
So Im assuming that the steam theory may be it along with a air pocket, so I used a coffee pot and refilled it so I could measure how much fluid it took to fill the crossflow radiator , and it took roughly 2 liters (67 fl oz) So the antifreeze fluid was way low....
I feel safe running the truck in the driveway and cruising my neighborhood to see if the fan kicks on again.
Thanks for everyone input
On a side not I found the power bar that is responsible for the power to the relay and Im going to make it a manuel versus automatic .

[MALIBLOC]

today I checked all the wiring and I have a few questions

The wire for the water temp sender was melting and I pulled the sheathing off and the wire underneath was fine do those senders go bad that often?

I opened up the relay and it didnt smell or look bad, can these go bad.

Lastly can I just jump the red wire to the battery and see if the fan works at all.

I have some alligator clips and I checked with my circuit tester and its hot at the relay but something is off.

[mongocanfly]

Anything electrical can go bad....
1st I would make sure the fan is good...if the fan ground is good then hook 12v to the red wire from the fan...it should run..

2nd i assume the big yellow wire at the relay is your 12v fan supply from the battery...make sure there is 12v on that wire..I think that's what your saying you tested with your circuit tester..if that's good then move on

Next check the signal wires to the relay...I can see some writing on some of the wires..
Does the gray wire say (sender)?
What does the orange wire say?...
I'm again assuming the gray wire goes to the sender
And the orange wire goes to your key switch on 12v power

Is the gray wire the one you say is burnt? If it is I'd replace the sender and the wire

Then next I'd replace the relay if the sender doesn't fix ix

Do you know the brand of the fan and relay?
There should be a fuse somewhere in there on the big yellow or big red wire..

[joedoh]

a relay is a low current to high current switch, meaning, you use a low current switch to connect a high current source to a high current demand.

think of it like a little tiny wiry guy who sees an indicator light and then tells a blind burly guy to lift something heavy. the big guy cant see the indicator, and the wiry guy cant lift the heavy thing, so they work together each doing what they can do.

on a std automotive style relay there are 5 pins.




pins 85 and 86 are your low current switch, your wiry little guy. in proper design you would put the sender wire on either 85 or 86, and then the OPPOSITE polarity of that sender on the other one. so if your temp sender is a grounded type switch you would attach it to 85 (or 86, pick one), and then attach 12v+ to the other. there is a coil inside that when it "sees" both 12v+ and ground on the pins 85 and 86, it energizes and closes the high current contacts.

pins 87 and 30 are your high current contacts. on 30 you put the wire to the high current device, and on 87 you put the high current supply, usually 12v+. you can reverse these in that application, using 30 as the input and 87 as the output, but I feel it is poor design because 87A is the NC (normally closed) output from 87, and if you use 30 as an input and need an NC output it will never work.

so looking at your relay, 85 is a blue wire from the sender, 86 is an orange wire. 87 is the output to the fan (that poor design decision I talked about but doesnt matter here because there isnt an NC connection) and 30 is the supply from fused 12v+.

you say you are melting the sender wire, did you hook up your trigger wire for manual operation yet? it is possible that you have hooked up a 12v+ trigger to a (-) sender, which would short it and melt the insulation.

if you have not hooked up a manual trigger yet, there isnt a lot of reason why the low current sender would be melting insulation, I would suspect a bad ground on the sender body if it is a (-) trigger sender, or a bad relay that is bleeding 12v+ onto the sender wire.

[MALIBLOC]

so the pigtail connecting the fan to the harness is fried. I disconnected it and the negative side of both pigtails is completely burned out. I cut the wires to the fan and grounded the black and put 12v to the fan and nothing. Im assuming the motor fried itself too. The ground wire was loose from what I see, fan was installed about 16 years ago.
Thank you for everyones help, Im going to call Spal Fans tomorrow with the part number and see what a replacement fan will run me. I need a 16" x 2.75" depth since I have limited room.

[mongocanfly]

Yep..thatll do it...do you have a inline fuse?

[MALIBLOC]

yes from the power source to the fan on the opposite side of the pigtail in the cabin of truck and it did not blow.

[burnin oil]

Sounds like the fan died and took the wiring with it.

[MALIBLOC]

Thanks again to everyone here for helping
The original fan still works!
It was my relay that was bad as well ass the pigtails
I went and hardwired the original fan with a switch and guess what it worked
but since i had everything apart I waiting for the new fan in and the relay should be coming in today.

Nest time check in this order
Check connections
Inline fuse
Check grounds
Check relays
check fan

[BlouDon]

IF there was somehow a poor connection from the female connector pin to the male fan pin over which it goes, you end up with a high resistance. This high resistance, coupled with the high amps that goes through it, results in heat being generated on those pins. The more heat, the more resistance, the more heat ..... and so on.

So now the question should be: IF it was poor connection, what caused the poor connection? The female pins being bent open too much is an obvious candidate but a high pressure cleaner being used to clean the engine is another. Few people realise that they spray water with such high force that water can easily be forced past the connector seals, become trapped inside the connector, which causes corrosion, which causes high resistance ... and there we go again...