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1948 - 1956 F1, F100 & Larger F-Series Trucks Discuss the Fat Fendered and Classic Ford Trucks

trouble shooting radiator fan relay/thermostat

 
  #1  
Old 04-13-2019, 05:23 PM
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trouble shooting radiator fan relay/thermostat

noticed on first few startups that the radiator fan isn't kicking on when temp on dash read 180 or even 220. The temp probe is stuck in the fins of the radiator toward the top of the core. I played with it a while... removed temp probe and tried heating it with a hair dryer while using a IR temp gun.. never got hot enough... then went for the big guns (heat gun) on lowest setting and watched the temp rise to 180 and up to 220... nothin... went a little farther and the thermistor destroyed itself. Guess I went a little more than a little farther...

got a new probe from Cooling components and have it in circuit now but wondering about testing again... kinda shy about heat gun. What is a good method ??? Pot of water with thermometer in it ??. I find lots of YouTube stuff about using a meter and checking resistance but I don't know how that crosses over to temperature. I need to find out if it's the probe or the relay/switch part and get the fan working. I can bypass and connect directly to fan and get both low and high speed.. but I need to see if the thermistor (on/off switch) is actually actuating or if my problem is downwind i.e. bad relays or other...

help the dummy ???

john
 
  #2  
Old 04-13-2019, 07:27 PM
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Not an expert here, but I'd be sceptical with the probe just stuck in the radiator fins. My 53 uses one that screws into the bottom tank of the radiator. Most use a rubber grommet that fits inside one of the radiator hoses.
I would use the pan of water and a thermometer to test for on/off temps.
This is the one I'm using.
 
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Old 04-13-2019, 07:40 PM
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I would check that relay to make sure the contacts are closing. Jumper out the coil, see if ya got anything.
 
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Old 04-13-2019, 11:10 PM
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Pretty sure the temp sensor needs to be immersed to work correctly. I would think behind the thermostat would be the best place to put it.

B
 
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Old 04-14-2019, 08:09 AM
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Old 04-15-2019, 10:20 AM
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I agree with all above that the sensor needs to be immersed. If the radiator ran a setup like this on a Volvo engine and it won't like a charm, but only when it sat in the coolant. Testing it the way you did didn't work for me either. Only problem is, some of those sensor have huge threads and you may need to get a 2 speed sensor in your temp range that fits in them.

If your radiator doesn't have a place to thread the sensor in, they cell aluminum coolant hose junctions that allow you to thread the sensor into the upper or lower hose, just need to cut the hose and splice it in. Ran that setup on yet another Volvo without a hitch. (Link below)

https://www.summitracing.com/parts/atm-2281/overview/

And relays are cheap. Grab another one and see if that could be the cause.
 
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Old 04-17-2019, 12:33 PM
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[QUOTE=jniolon;18598914 What is a good method ??? Pot of water with thermometer in it ??. I find lots of YouTube stuff about using a meter and checking resistance but I don't know how that crosses over to temperature. I need to find out if it's the probe or the relay/switch part and get the fan working. I can bypass and connect directly to fan and get both low and high speed.. but I need to see if the thermistor (on/off switch) is actually actuating or if my problem is downwind i.e. bad relays or other...

help the dummy ???

john[/QUOTE]
John

I went through getting my cooling fan and controller sorted out last summer. I think testing the probe in water near boiling is a good test, and safer, if you don't spill the water on yourself.
The thermostat closes the circuit at a setpoint so I would try jumpering out the thermstat contacts to the controller, to test your controller circuit. That should isolate the problem. You probably already know that the thermostat is compatible to the specific controller, and the controller may have an adjustable range setting.
 
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Old 04-17-2019, 02:50 PM
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I went back to your original post. Like Tom mentioned a pot of water with a thermostat in it seems like a good way to test it. I am not sure how the aftermarket fan kits are wired. On heavy duty truck systems the switch is normally closed and opens when the preset temp is reached. (https://www.hortonww.com) Your system may use a normally open switch which closes when the temp is reached. A good normally closed switch would show resistance across the terminals until it reaches the preset temp at which point the switch will open and there will be no more resistance across the terminals. A normally open switch would work just the opposite. As far as the correct temp for the switch to open or close it should be stamped on the side of the switch.

B
 
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Old 04-17-2019, 08:04 PM
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I would think that it is no good just stuck in the fins .
It needs to be immersed in water to work as it should , and the best place is around the thermostat housing somewhere .
Mounted in the rad fins it would never be accurate as it would have air moving over it keeping it cool , and probably never kick in until your engine was cooked .
 
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Old 04-17-2019, 11:42 PM
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Hey John,
We have a 351W in our truck and the mustang guys sell
a thermostat housing that has an extra bung in the top of it where you can
mount the temperature sensor. I would guess the after market guys have one for your engine as well.

We used a BMW (2) speed temp sensor for our set up. I think the first speed is triggered at around 185
& the second higher speed at 195. They use Celsius so it's not quite those numbers but close.

Good luck over there!

Ben in Austin
1950 F1
 
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Old 04-18-2019, 09:30 AM
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Sorry for the slow response, been busy with 'get ready for Easter yard work and 30-35 family lunch group. I agree that the best switch would be immersed in the flow but the controller supplied with the fan has the probe that is inserted into the cooling fins. I can see the difference in accuracy, but several fan controllers and a/c probes are just this kind. I'm just trying to make what I bought work correctly. The controller has a base with two relays in sockets and the appropriate wiring to function. Everything is potted in the base and tracing leads and such is impossible... CCI wouldn't (or couldn't) provide a wiring diagram. Several specific questions about probe and circuits were answered with "I'm not sure " or "I really don't know".

The pot of water technique is the only safe solution for a test that I could come up with. I tried using a heat gun and a IT temp gun to actuate the probe and read the temp but I could never get an accurate read (trying to hold that red dot on a probe 1/8" wide is hard) and I was successful in destroying the probe... it came apart !. A new probe was ordered and attached and before I install it all again I just wanted to give it a test and determine the
temperature range. The controller has a rheostat that is adjustable for start temp.

As for the other suggestions of where to put a probe.. I have no room for the thermostat housing type as I had to fabricate my own housing due to interference with the big ole honkin DUI distributor.



Question... if it is necessary to use a immersed probe... could it be inserted inline with the drain petcock and get an accurate reading... I know there isn't a lot of 'flow" down in the bottom, but the temp should be reasonably accurate... although it would be the 'already cooled' temp , wouldn't it ?? . I answered my own question, didn't I ?? never mind
Before I decide to install the adapter in the radiator hose (and spend another 80 bucks) I'd like to see if this already bought controller will do the job.. if not ?? well, what's 80 bucks in this project. Another negative is that the adapter in the radiator hose will look like crap on top of the engine.

Plan A... I can't find my single eye hot plate so I'll buy one today and try the hot water test. Both immersed thermometer and IR gun will be used to check water temp and see what happens... if that doesn't get results
Plan B... come back here and regroup

thanks B, Tom, Seaves, Ben and all for the replies... at least you got me thinking and pointed correctly

j
 
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Old 04-18-2019, 06:03 PM
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John ,remove your top rad hose and insert the probe into the hose and refit it .
The hose clamp should seal where the hose and probe are .
That's how my 34 ford was done with a 302w .
 
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Old 04-18-2019, 06:26 PM
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Probe can be put anywhere in the coolant, core plug, intake manifold runner, upper radiator hose, radiator tank, etc..On my non computer car with an electric fan I used an adjustable fan controller kit, so I could make the fan kick on at 190 degrees no matter where the sender was mounted (180 thermostat). Sender in the cylinder head will read higher than actual temp, other places may give different readings as well, but with the adjustable unit you just turn the potentiometer until the fan kicks on when you want it to. On my computer controlled fans with two sending units (one for gauge, one for PCM) I read about 10 degrees hotter in the cylinder head vs water pump.
 
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Old 04-19-2019, 01:50 PM
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Progress report... got a hot plate today and set up for the test. Brought the water up to 180 deg and inserted the probe...and waited... nothing. Raised the water temp slowly to 220 and waited.. crickets.

Then I cut the probe out of the circuit and shorted the two leads and repeated the test... nothing. Tested the probe with a ohm meter as I applied heat (using a non industry calibrated candle)... resistance rose as the temp was
read on the thermistor. Haven't got a clue what the temps were... but at least that part of circuit is good.

With great mental anguish I cut the entire controller circuit out of the truck and took it to the bench. I applied voltage where it was needed and grounds where they should be.. Since it was all potted and no leads could be traced I pulled the relay (high speed) and I did some voltage testing and found 12vdc at the coil input and 12 vdc at the input for the load. So.., one more step is good. I stuck the relay back in the circuit leaving enough room to get a slim test lead between socket and relay spade. When I shorted out the thermistor there was no click in the relay and no voltage on the load side of the relay.. Did this on both the low speed and high speed circuits...same result.

Next I verfied another relay from stock on hand and it was working properly... put it in the socket and tested again... same result... nothing as before.

Now, with my extremely high intelligence and infallible test procedures I've deduced that something down inside that potting material is hosed. I'll be back on the phone with CCI and see if I can get some resolution... since this unit is a few years old, I'm not confident in the outcome

later that same day...I talked to CCI and explained all this and we both agreed that the controller was bad out of the box... no granted that it was in the box 6 years but had never been installed... and he agreed. His excellent customer service answer was "I'll give you a discount on a new solid state controller... regular 189 for 159 + shipping" Boy, what a deal... I asked him if his solution was for me to spend 159 plus shipping to correct a bad component bought new. and he said "Yes, we had problems for years with that unit" I thanked him for his excellent customer service and told him I go with a reputable company and get something that works correctly. He hung up.

ok... recommendations for fan controllers... go

john
 
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Old 04-19-2019, 03:37 PM
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