Electrical questions

[BFS57]

Hello;
I have a 32 hot rod that had the battery under the floor. I just changed that to the rear of the car for  a bigger battery (group 24). I still have the drop down battery box mounted under the car.(smaller sized battery)
What I am thinking is that my electric fan really does suck the juice and when it runs, if I go to start the car, while it's running, there's not enough power left to turn the engine over. So I had this idea to put another battery back in that under car box and just hook the fan up to it's own battery.
Anyone got any help, pro or con?
I could also wire a switch from the fan controller to inside the car to switch off the fan just long enough to start the car.
The fan is one of those Cooling Componants fans that come with the Walker radiator.

Bruce

[PeterR]

Hello;
I have a 32 hot rod that had the battery under the floor. I just changed that to the rear of the car for  a bigger battery (group 24). I still have the drop down battery box mounted under the car.(smaller sized battery)
What I am thinking is that my electric fan really does suck the juice and when it runs, if I go to start the car, while it's running, there's not enough power left to turn the engine over. So I had this idea to put another battery back in that under car box and just hook the fan up to it's own battery.
Anyone got any help, pro or con?
I could also wire a switch from the fan controller to inside the car to switch off the fan just long enough to start the car.
The fan is one of those Cooling Componants fans that come with the Walker radiator.

Bruce

Fit a normally closed relay at a convenient place in the supply to the fans.   Then a light wire from the S terminal on the starter solenoid to the field pin of the relay.

When the key is turned to START, the fans will stop, then start up again once the engine fires and the key is back in the RUN position.

[rumrumm]

I agree about the relay. In addition, if you are running a one-wire alternator, switch it back to a three-wire set-up. That way it will sense a draw and compensate. A one-wire set-up will not do that. I learned that the hard way.

[BFS57]

Hello;
I like the answer about the relay. I know a little bit about relays but the description "normally closed" I don't understand or "what "terminal" would be the field terminal?
I can get to the "s" terminal on my starter quite easy! It's just running the wire (and keeping it hiden) that might be a problem.
Yes, I do have a single wire alternator on this car and I think it has the provision to go 3 wire, I just have to do some looking in a couple wiring books to see how to wire that up.
Did I mention that my battery is now the Optima red top? Powerful 800 CCA!
What if I did boath mods? relay + 3 wire?

Bruce

[kb426]

Normally closed means without power the contacts are closed passing juice. Normally open means that until the coil is energized, the juice doesn't flow. I would do both mods without question. I used a Centec fan controller on my 32. It is temp adjustable and has an overide switch for what I call parade mode. If you're going to cruise slowly, you turn on the fan before it's time. It helps keep the heat from building.
This is the style I'm referring to.
http://www.delcity.net/store/Relay-&-Socket-Harness-Kit/p_72563

[PeterR]

Hello;
I like the answer about the relay. I know a little bit about relays but the description "normally closed" I don't understand or "what "terminal" would be the field terminal?
I can get to the "s" terminal on my starter quite easy! It's just running the wire (and keeping it hiden) that might be a problem.

Bruce

As kb426 indicated, a conventional relay has the contacts normally open (NO), then when the coil is enenergised the relay flips and the contacts close.

A normally closed (NC) relay has the contacts closed until the coil is energised then they open.  

A changeover relay such as http://www.delcity.net/store/5-Pin-Relays-with-Mounting-Bracket/p_73576 can be wired as NC or NO.



When there is no power to the starter solenoid, relay terminal 30 is connected to terminal 87a and the fans operate normally.

During cranking the coil is energised, and disconnects 30 from 87a causing the fans to lose power.

[wayne petty]

i have a crazy idea.. are you running a thermostat.. and some kind of bypass to keep the coolant circulating in the engine block and heads until it comes up to temp. then just opens enough to swap the cooler coolant from the radiator with the hot from the engine then closes again???

with a thermostat you can run a fan thermostat so the fan only runs when the hot coolant is exchanged into the radiator..  where it will be cooled by the fans and they can turn off awaiting the next surge of hot coolant when the thermostat opens..  this is automotive cooling system normal operation.

running electric cooling fans constantly can actually get the armature shaft hot enough to melt the center out of the fan blade on some model fans. . they were never designed for that kind of constant operation..

cycling the fans off and on with proper thermal controls.. will allow the battery to come up with the current the alternator is putting out.

by the way... you might want to create some LONG LONG TEST leads or lay a pair of jumper cables under your car on the ground and only hook up ONE at a time to the battery clamps.. so you can perform all six steps of this test up in the engine compartment..  http://i.imgur.com/WMDprhm.jpg  

i think there was also talk of running a relay to power the fans directly off the alternator output. yep..  that will reduce voltage loss.. you might want to do it off the starter top post.. but either will work..  you can perform the voltage drop test on the fan wiring also.. to make sure its not undersized..

just a few thoughts in the middle of the night..

i have been trying to stay away and just lurk .. but i have big feet and need to dip my toes in once in a while to stir the waters..

[BFS57]

Hello;
I am running a FlexALite controller. #31149 It has a radiator probe to get temps from, an adjustment knob to set fan on and off, a hook up for the AC Compressor, and a provision for a switch to be hooked up inside the car. The fan comes on and cycles when the temp drops.
When the fan is running, the draw is tremendous! I am thinking that the Idea with the relay seems the best, just short of installing a switch. I did install a switch on the output to the fan but it failed. This thing has some serious draw. I would have to find a better switch or hook up the switch on the controller where it is supposed to be, run wires to the inside and "find" a place to mount it. Thats why I like the relay idea, Everything hooks up inside the engine compartment and it's kind of an "automatic" feature.
Changing the alternator from a single wire to a 3 wire is something I have wanted to do but is dificult because this car doesn't have any idiot lights and I would need a diode in the hook up to make the engine stop when the key is turned off (Don't know that much about that kind of stuff)
Wayne, I like the voltage drop test but my car is fiberglass and does not conduct electricity. I have constantly faught for really good grounding on this car, it's much better now but believe me, I still have gremlins from time to time!

Bruce

[wayne petty]

if you dig around.. you can actually get 70 amp relays in an ISO configuration except they use 3/8" quick connects instead of 1/4" ..  they are cheeper elsewhere.. usually..

http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Accessory-Relay/_/R-LIT195_0006417776

a 70 amp relay, socket with 12" wires http://www.speedwaymotors.com/American-Autowire-500511-70-Amp-Relay-and-Plug-w-12-Inch-Pigtail-Only,46192.html

heck you can even rob versions of these from volkwagen rabbits and golfs..

in a kit.. with a proper fuse.. http://www.summitracing.com/parts/rfw-ar70/overview/  i don't recall if you had a single fan or a pair of fan motors..

if one wants to do a little junk yarding.. some chrysler minivans have a solid state radiator fan relay mounted behind the bumper in the core support down low where it can get lots of air flow to cool it.. these can usually be engineered to work..  no moving parts.. but also if the car does not pass my six part voltage drop test.. expect it to burn out..

just a thought..

[tomslik]

wayne, the failure rate is so bad on the mopar fan relays, I wouldn't use one on a bet

[wayne petty]

wayne, the failure rate is so bad on the mopar fan relays, I wouldn't use one on a bet

i have found that also.. but usually its loose or dirty grounds that cause them to overheat and fail..  start performing this test and watch the failure rate drop. http://i.imgur.com/WMDprhm.jpg..

[PeterR]

Since posting the wiring diagram above I have looked at the 31149 controller wiring and notice the thermostat function will only work while the + terminal is connected to ignition power.   This means you could install the start lockout relay in the fan supply wire as shown above, OR in the ignition wire to the + terminal.

If you fit the relay in the fan feed, the relay carries the full fan current; however if fitted in the ignition supply it is only carrying signal current which means you do not have to be so fussy about the current capacity of the relay.

But there is a downside. If the aircon is switched on while you are cranking the engine, the fans will continue to operate (as the aircon trigger   functions even if the ignition feed is absent).  

This opens up another consideration in regard to your battery issue.  If the aircon is on while cranking, the battery is supplying power to magnetic coupler, and is subject to the additional load of spinning over the compressor. It would be very easy to fit a start lock out relay to the aircon  which would automatically avoid this unnecessary load on the battery during cranking.

[BFS57]

Hello;
I always make sure the AC is off before cranking the engine so I don't see that as a problem.

Bruce