'38 ford pickup electrical Q

fordt1926 · 04-22-2008, 11:31 AM

My truck has been converted to 12 volts and has an electric radiator fan. There is no fuse built into the circuit when the fan was installed. The fan wire which attaches to one of the three brush terminals on the ignition switch body smokes yet the fan motor runs well. Am I correct to assume that (1) there is either a short in the wires coming from the fan motor or (2) the fan motor is shorting out (although it still does run).
Thanks

mrjohnwayne · 04-22-2008, 12:33 PM

could be any of the following.

1 bad wire connections (either on the hot wire or ground wire)
2 bad fan
3 bad switch
4 short in the wire(s)

in no particular order. I would introduce a fuse to the circut as well.

75K30 · 04-22-2008, 12:40 PM

Holy smoking switches Batman! How long has this switch been smoking like that?
Sounds to me that the load on the switch is too great, and heat is melting the switch. It will eventually, run out of "magic smoke" and fail. It usually catches fire right about this time. Seriously, this is a problem.
You need circuit protection, and you need to isolate the load by installing a relay. You will need a relay that can accomodate the load requirement of the fan. You will then wire the coil on the relay to energize and close when you need the fan. This can be activated by a heat controlled switch that is available at you local auto parts store. This auto supply house will also have the relay, and wiring diagram to help you out.
Should be a simple fix, but you need to take care of it before you smoke your truck down.

crabtruck · 04-22-2008, 03:42 PM

^^^^major agreement, scary !
Got to be careful with those newer trucks (well compared to the 1926 one)
A suggestion: use the wire coming from the key to control the new fan relay.
Disconnect it from fan and hook it to relay. Then power fan through relay
from the battery. Like 75 said, too much power going through key.
You can cut that key wire between key and relay to put in the temperature switch he mentioned.
Check that you haven't melted too much of the switch or nearby wires.
Overloading can cause melting at any point in the wire run, look around.

04-22-2008, 11:31 AM	#1
fordt1926 Junior Member Join Date: Nov 2006 Location: CT Posts: 5	'38 ford pickup electrical Q My truck has been converted to 12 volts and has an electric radiator fan. There is no fuse built into the circuit when the fan was installed. The fan wire which attaches to one of the three brush terminals on the ignition switch body smokes yet the fan motor runs well. Am I correct to assume that (1) there is either a short in the wires coming from the fan motor or (2) the fan motor is shorting out (although it still does run). Thanks

04-22-2008, 12:33 PM	#2
mrjohnwayne Senior Moderator Join Date: Apr 2005 Location: Texas Posts: 3,789	could be any of the following. 1 bad wire connections (either on the hot wire or ground wire) 2 bad fan 3 bad switch 4 short in the wire(s) in no particular order. I would introduce a fuse to the circut as well. __________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4

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04-22-2008, 12:40 PM	#3
75K30 Senior Member Join Date: Jul 2006 Posts: 3,312	Holy smoking switches Batman! How long has this switch been smoking like that? Sounds to me that the load on the switch is too great, and heat is melting the switch. It will eventually, run out of "magic smoke" and fail. It usually catches fire right about this time. Seriously, this is a problem. You need circuit protection, and you need to isolate the load by installing a relay. You will need a relay that can accomodate the load requirement of the fan. You will then wire the coil on the relay to energize and close when you need the fan. This can be activated by a heat controlled switch that is available at you local auto parts store. This auto supply house will also have the relay, and wiring diagram to help you out. Should be a simple fix, but you need to take care of it before you smoke your truck down.

04-22-2008, 03:42 PM	#4
crabtruck Senior Member Join Date: Jul 2007 Posts: 4,128	^^^^major agreement, scary ! Got to be careful with those newer trucks (well compared to the 1926 one) A suggestion: use the wire coming from the key to control the new fan relay. Disconnect it from fan and hook it to relay. Then power fan through relay from the battery. Like 75 said, too much power going through key. You can cut that key wire between key and relay to put in the temperature switch he mentioned. Check that you haven't melted too much of the switch or nearby wires. Overloading can cause melting at any point in the wire run, look around.