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Cooling fan problems
#1416403 Fri Jul 09 2021 03:00 AM
Joined: Aug 2009
Posts: 149
O
'Bolter
I have apparently destroyed my new cooling fan and need some help regarding wiring. Background: I just installed a new aluminum radiator, shroud, and electric fan into my 1957 3600 which is powered by a 350 engine with 700R4 transmission.
After a 30 minute test drive the cooling fan stopped running and of course the engine temp began to rise. To troubleshoot, I unplugged the fan connector and connected test leads directly to a 12 volt battery to verify the problem was actually the fan and not a temp sensor, relay, etc. I then connected a multimeter to the input side of the fan connector to check input voltage. The meter indicated 16.2 volts input to the fan. I assume this is what fried my fan motor. The fan installation directions indicated I should run a wire with fuse directly to the battery. Since my battery is underneath the truck bed and I wanted to avoid a very long lead to the battery, I elected to instead, connect the fan relay to the output pole of the one wire alternator (with a 30 amp cicuit breaker inline).

Is my problem caused by connecting directly to the alternator? Is my alternator output too high at 16.2 volts, thereby destroying the fan motor? Note: the in dash volt meter usually indicates from 12.2 up to 14.2 volts.

All help is appreciated, especially solutions that go beyond "remove the new fangled electric fan and install an engine driven fan".

Thanks


Oldbolter
1959 Apache 3800 dually flat bed/dump with 261

1956 3800 dually flat bed/dump with 235

1957 3600 flat bed, 350 engine, 700R4, PS, disc brakes, 14 bolt rear with 4.11 gears
Re: Cooling fan problems
oldbolter #1416410 Fri Jul 09 2021 03:51 AM
Joined: Mar 2010
Posts: 610
B
Curmudgeon
With the fan disconnected, use your meter to check the resistance of the motor at the fan connector.
Let us know what you read.

Re: Cooling fan problems
oldbolter #1416412 Fri Jul 09 2021 04:04 AM
Joined: Jul 2000
Posts: 1,311
G
Insomniac
I6.2 V shouldn't burn out a 12 V fan.

Maybe the connection to ground failed during the test drive.

When you tested the fan, did you run 2 wires from the battery? (- to - and + to +)


Gord
----
1954 1/2 ton 235 4 speed
Re: Cooling fan problems
oldbolter #1416420 Fri Jul 09 2021 11:40 AM
Joined: Feb 2004
Posts: 23,008
H
'Bolter
Fix the charging system first, then worry about the fan, since you're choosing to ignore the right fix.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Cooling fan problems
oldbolter #1416483 Sat Jul 10 2021 01:28 AM
Joined: Aug 2009
Posts: 149
O
'Bolter
Thanks for all the replies
buoy maker: If I measured resistance correctly, it is .01 ohms.
Gord; Yes, I connected the 2 test wires to the battery as you described.
Jerry: I plan to take the alternator to the repair shop Monday.

Question for all: Is it okay to connect the fan relay to the alternator as I have done instead of directly to the battery?

Thanks to all.....


Oldbolter
1959 Apache 3800 dually flat bed/dump with 261

1956 3800 dually flat bed/dump with 235

1957 3600 flat bed, 350 engine, 700R4, PS, disc brakes, 14 bolt rear with 4.11 gears
Re: Cooling fan problems
oldbolter #1416487 Sat Jul 10 2021 02:15 AM
Joined: May 2015
Posts: 4,203
Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums
Any wire connected to the battery (and anywhere along it, including at the alternator) will read battery voltage with the engine not running, and charging voltage with the engine running.

That assumes that the wires are the correct gauge for the current it's expected to carry.

So, yes, connecting the fan relay to the alternator should work just fine.


Kevin
First car '29 Ford Special Coupe
#2 - '29 Ford pickup restored from the ground up.
Newest Project - 51 Chevy 3100 work truck. Photos [flickr.com]
Busting rust since the mid-60's
Re: Cooling fan problems
oldbolter #1416530 Sat Jul 10 2021 02:59 PM
Joined: Mar 2014
Posts: 2,481
J
'Bolter
I don't know what fan size, cfm rating, etc you have, and I don't know what make. In my opinion Spal makes the best ones (Italy) followed very closely by Flex-A-Lite (USA). It should have around 30 ohms resistance (leads not connected to anything...just resistance across the fan motor). If the resistance is .01, that is basically an open circuit and tells me your fan motor may be gone. Good luck.


Jon

1952 1/2 ton with 1959 235
T5 with 3.07 rear end
Re: Cooling fan problems
oldbolter #1416534 Sat Jul 10 2021 03:10 PM
Joined: Jun 2011
Posts: 4,205
E
'Bolter
Rather than running a wire all the way to the battery, hook the positive lead to the plus terminal on the starter.

Ed


'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
Re: Cooling fan problems
oldbolter #1416538 Sat Jul 10 2021 04:00 PM
Joined: Mar 2010
Posts: 610
B
Curmudgeon
Open circuit is infinity (∞) or maximum resistance. 0.01 ohms (probably using a digital multimeter) would be a short.
You used a "30 amp circuit breaker inline" rather than a 30 amp fuse? If so, the breaker has a time delay to open to protect the circuit.
Unfortunately it can give more time for other parts to fail as well.
Usually the fan manufacturer provides a recommendation of fuse type and amperage rating.

Last edited by buoymaker; Sat Jul 10 2021 04:11 PM.
Re: Cooling fan problems
oldbolter #1416543 Sat Jul 10 2021 06:35 PM
Joined: Mar 2014
Posts: 2,481
J
'Bolter
It is and thanks for catching that...thinking backward this morning, I guess.


Jon

1952 1/2 ton with 1959 235
T5 with 3.07 rear end
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