I wired in an electric fan into my 40 and used a Spal Relay Wiring Harness. I am using the original 40 Ford ignition switch. I am powering both the yellow, and the orange off a Ford style starter solenoid. If the fan isn't running when I kill the ignition switch the car shuts right off. If the fan is running and I kill the ignition the car continues to run for a second or two and then shuts off. I am not using the optional cooling fan override switch. Do I need a resistor? and if so, where and what type? or should I pull power from another source for the Orange lead?
The fan is working as a generator and is feeding the ignition. The fan needs to be isolated from the ignition and put on it's own circuit.
Put a diode between the orange wire and the ignition switch. It will stop the fan backfeeding the ignition.
Yes. The fan should be fused from the battery. It's feeding back through the ignition, that's why the car stays running when the fan is on, and shuts off fine when the fan isn't running. Had the same problem with a car I worked on at an electrical shop. It kept burning up expensive MSD ignitions. The fan was causing the problem. We isolated the fan power supply and the problem went away.
The solenoid (under the dash) was a convenient place to hook-up. There are feed's I can tap into at the fuse block, how can I check to see if they are isolated or do they typically have some circuitry on the back plane of main panel to isolate? It's an aftermarket 8 or 12 circuit of unknown manufacture. I need to do a little research.
The problem is the relay isn't connected to the ignition switch. If it were wired as per the diagram, you wouldn't have any issues. Connect the orange wire to a switched hot as shown and you'll be good to go. If you don't want to do that, then put a diode in line on the orange wire to prevent backfeed.
The problem is the orange wire ISN'T connected to the ignition switch; in effect, both the relay and fan power are connected to the same point. Connect to a switched hot as shown in the diagram and it'll work fine. If you don't want to do that, then install a diode in line in the orange wire. A switched hot connection will be more reliable. What's happening is the fan is operating as a generator after the key is turned off and the backfeed power is enough to hold the relay in for a few seconds. Keep in mind that the only way to 'isolate' a circuit in a basic 2-wire DC system is to run one wire through a switch. All circuits tie back to a single point, the battery....
I had the orange to the back of the ignition switch and had the same back feed issue. I then moved it to the I terminal of the Solenoid (which is jumpered to the Bat side) and had the back feed issue as well. I could use a diode, Do I want the Anode towards the voltage source, and Cathode stripe toward the relay?
Cathode goes to the relay. If you use a diode, make sure it is able to handle the forward current (In this case 1 amp should be OK)
Found this on a Mustang Forum and using a Diode between the positive and negative of the Fan Motor. This seems like a good fix as well. The diagram shows how to use the fan controller to fire the Bosch relay. A reverse current blocking diode (or freewheeling diode) is a good idea on any motor control relay. Once power is removed from a DC motor it becomes a DC generator and the reverse voltage spike can shorten the life of the relay. The diode will bleed this spike to ground. The 1N5408 diode can be found at any electronics store for just a few dollars.
If you had the orange wire connected to the SWITCHED side of the ignition switch and still had this problem, you've got an interconnection somewhere else that's causing the problem. So let me ask about the Ford solenoid. Are you using this as a relay? Battery power connected the 'batt' side, various other loads connected to the 'starter' side, with a switched hot connected to the 'start' terminal? First thing I'll point out is these aren't rated for continuous duty. Sure, the contacts are plenty beefy, but the coil isn't rated for continuous use. It will fail, sooner or later. Cole-Hersee makes a 85 amp relay with bolted connections rated for continuous use, about $25. Even heavier-duty ones are available, check McMaster-Carr. If you are using the solenoid as a relay, are you connecting the fan and fan relay to the 'starter' terminal? If so, there's two possible fixes; one, move the fan power to the 'batt' terminal. Disadvantage here is if the SPAL relay fails closed, the fan will run continuously. Two, leave the fan power alone and move the SPAL relay power to the 'start' terminal on the solenoid. If there's no other interconnections downstream, this will fix it. Still not fixed? At this point you can do a diode, see the above post.
Well Damnit, I tried two solutions and neither work. First I assembled an inline assembly with spade connectors on each end. I installed that into the orange ignition Cathode stripe towards the relay. It still back fed in this condition when I throw the switch. I turned it around and the fan wouldn't run. I left it in place and then decided to install a diode jumpered (soldered) between the positive and negative lead at a connector 6" from the fan. Stripe (Cathode) towards positive lead like the pic. Fan kicks on and runs fine, but when I shut off the ignition switch it is still back feeding. In both tries I used a 1N540X 600V style diode. I had a helluva time finding diodes......No radioshack around, finally found and old electronics shop that had some. Bad diodes? How do they fail? Also wondered if the Alternator is charging harder when the fan is running and if the back feed could actually be from the Alternator....but it is a one wire??
We gave you bad advice when we told you to use a diode on the orange wire... as you now know. I doubt if the diode is bad. If you want to use a diode, either connect it as shown in post 13... Correction; well, it seems you tried that. My guess here is the pass-though current on the diode is low enough that there's still adequate current to keep the SPAL relay pulled in for that moment. So.... ...you'll need to install it in the power feed wire to the fan. The problem with this method is the diode will need to be rated for the fan running current plus at least 200% more (for the starting inrush). So I doubt very much that the one you have will work. Look again at post 14 for alternate switching solutions.
Thanks for the suggestions to date.....Just to verify I am not using the Ford solenoid as relay and I do have both leads attached to the BAT side. I did discover that the Fuseblock Is a Haywire 7 Circuit for a T-Bucket.....So not a lot of places to try and pull power from. I think I will give them a call tomorrow for some advice.
Ok, so the solenoid is just a solenoid and both wires are connected to the same point. You need to get that orange wire connected to a switched hot that ISN'T common to your ignition system. So what exactly do you have connected to the ignition switch? If that's the ONLY switch that switches power on/off (and it's a single-position switch), moving the orange wire may not fix the problem.
Just wire it like the first diagram. Battery goes to one big terminal. Fan goes to other big terminal. "S" terminal of the relay goes to the ignition switch. The sender unit looks to be miswired in the drawing. It probably needs to be moved to the minus side of fan. The fan gets grounded thru the sender unit. In no case should the "I" terminal on the relay be used for the fan.
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