Electric Fan Install

[Lbs]

I have a 1973 cuda with a 340 and I'm converting the cooling fan to and electric one. Got it all installed and hooked up today and as luck would have it, it's not working just right. When I adjust the thermostat to make it come on when the motor isn't running it works fine. I start the motor and adjust the thermostat and it blows the fuse. I have it wired so it's hot all the time so it will run for a few minutes after the key is off if it needs to. I'm drawing power at the starter relay, then a 20 amp fuse, then a relay, then the thermostat and finally the fan motor. The fan motor draws 11.5 amps according to the paperwork. Any help would be greatly appreciated. Cheers

[cudabob496]

electric fans only seem to work (ie cool adequatley), if you have an aluminum radiator, but that's another story.

see if powering your fan off the battery directly solves the problem.

if you have a 20 amp fuse, and its blowing, then for some reason you got more than 20 amps running through your wiring job.

Is your engine well grounded?? With a hefty ground strap?

are you using a relay setup for the wiring job?  probably should be.  If you are, is it wired correctly.

[GoodysGotaCuda]

Please post a basic sketch [even hand drawn] of how you actually wired it in the car. Relay, grounds, power, etc.

[Lbs]

Not a great schematic but hopefully you can see what I've done and if not let me know and I'll get you more. I haven't tried it directly off the battery yet because I have to get more fuses. Thanks for your help

[Lbs]

I'm looking at my picture and to be clear, my wiring started at the starter relay. Thanks, Mike

[GoodysGotaCuda]

Your wiring looks completely fine. Unless it's undersized or there is a short to ground, I would make the assumption that you are seeing a "Startup Current".

The fan current draw of 11a you mentioned is usually a "running" current draw. When starting, there is a higher initial hit, or spike, in current. This could be peaking past your 20a fuse.


If the wiring is adequately sized and wired just like it is in your diagram, I would step to a 25a or 30a fuse and try that.

[brads70]

is it a dual speed fan? If so they will draw more on start up if wired as a single speed. My electric fans used 30 amp fuses. , they are both dual speed and each fan has two 30 amp fuses.

[Lbs]

Not a duel speed fan so I think I will try increasing the fuse amperage. My wire size should be more than adequate. The only thing that is still bothering me is that the fuse doesn't blow when the car isn't running. :Dunno. I'm going to try the higher amp fuse and see how it goes. I'll post the outcome soon. Thanks guys

[moper]

It sounds like the wire is not heavy enough. What gages of wire were used to make the various connections? Personally I don't like coming off the starter relay - either use a positive buss under the battery or wire to the battery terminals (like many ignitions require).

[Lbs]

The wire gauge from the fuse link is 10 and everything else is 12 and 14. The fan motor itself has 14 coming off of it so that's my smallest wire. I increased my fuse amperage to 25 amps and put the car thru its paces, headlights, heater, defroster and the cooling fan all running at the same time while driving around for a while and everything seemed to be great..........except...........with everything off but the fan, my amperage gauge seemed to be buried to the charge side almost constantly when the RPM's were up. Does that mean my stock alternator is not putting out enough? :dunno

[brads70]

My aftermarket alternator ( advertised at 100 amps) was not enough to power the single fan I was running at the time. I do have a few other electrical add on's like MSD, Fuel pump......
I had to upgrade my alternator to this ..... I got the 250 amp version....
http://www.qualitypowerauto.com/item_557/Chrysler-Mount-Mega-Amp-Alternator.htm

[cudabob496]

maybe he needs to do the bulkhead bypass electrical mod. Run a 10 or 12 gauge wire directly
from the alternator output to the starter solenoid.


Also, I have a 10 amp elect fan coming off the  starter solenoid, using a relay
system, and it works fine. Most likely it's a wiring error.

[brads70]

maybe he needs to do the bulkhead bypass electrical mod.

That's always a good idea electric fan or not....

[TelisSE440]

The wire gauge from the fuse link is 10 and everything else is 12 and 14. The fan motor itself has 14 coming off of it so that's my smallest wire. I increased my fuse amperage to 25 amps and put the car thru its paces, headlights, heater, defroster and the cooling fan all running at the same time while driving around for a while and everything seemed to be great..........except...........with everything off but the fan, my amperage gauge seemed to be buried to the charge side almost constantly when the RPM's were up. Does that mean my stock alternator is not putting out enough? :dunno

If it is the stock alternator, it will not put out enough for the fans, along with the other devices. It will work for you if you put bypass wire from the alternator directly to the starter relay and don't work with everything on, all the time... You don't need to anyway so you'll be ok, but if you are working the electric devices constantly, you'll have to upgrade the alternator along with the wiring

[Lbs]

From what I am getting here, I should get a stronger alternator and I would be wise to run a new 8 gauge wire from my new alt to my starter solenoid. I am sure their are some details that I will need to know before doing the bypass so I will get some parts together and hopefully you guys will let me pick your brains some more to get this done. Thanks everybody for all the good info, have a great weekend and cheers to ya!