Ignition and electrical fan problem

[bigpat1802]

I have a Mark VIII fan and a 75 amp Bosch relay, and I'm switching it on manually through a toggle switch.

I hooked it up according to a diagram I found on a Ford site and figured everything was correct.



This is how I have it wired through the relay: One wire directly to the battery through a 30amp fuse. One to a 12+ ignition. One to the fan. One to the toggle fan switch.

I can turn the fan on without the ignition on. When I have the car running the fan will not turn on. If I turn the fan on and then start the car everything is fine until I turn the ignition switch off and the car and fan continues to run. UH OK! So I turn the fan off and the engine shuts off.

I'M CONFUSED! Help Please!

[shep]

Something is very wrong.
The relay should have the contact pin 87 wired to either the fan or the battery and the common pole pin 30 to which ever the the other isn't connected to. The trigger and ground wires for the relay pins 85 and 86 wiring depend on how you want the fan to operate. If you want it to only work when the ignition switch is on ground pin 85 or 86 and run the other to the switch and your switched 12v to the other side of the switch. Now it will only come on using the switch when the ignition switch is on.
If you want to be able to control the fan with out the ignition switch being on. Wire pin 85 or 86 to the same pin the battery is connected to run the other of the two to you switch in the dash and ground the other side of the switch. Now you can switch the fan on any time, By using a ground to trigger the relay there isn't any risk in the wire getting chaffed and shorting out.
Make sure either way you wire it you use a fuse between the relay and the battery. There are other ways to wire it but these two are the simplest.

[bigpat1802]

Here's the diagram I used:




My problem was I had the fan tied into the same 12+ ignition source as the computer, which is why the car wouldn't turn off when the igniton was turned off. I wired the fan to another power source directly off the fuse block and the fan won't turn on at all.


Shouldn't the fan work with the diagram I used? Since it doesn't work I'm hoping its not a bad switch.

[shep]

If you use that diagram with out the optional switch the fan should come on as soon as you turn the key to the on position. If you use the optional switch it will have to be on and the ignition switch on for the fan to come on.

[bigpat1802]

Yeah and it wasn't turning on when I had the car on.

I like the diagram that I posted up because it is running off the ground part of it.

I'll try another switch and see if that was the problem. I can't see that I burnt the toggle switch since its running through the ground.

[MonzaRacer]

AS for me I generally dont wire like that. I run my relays and fans separate from ignition control.
For power to the relay I generally have one of the (stereo)brass junctions fused at battery, this lets me power many items easily. I pull power from that to relays 30 terminal, Ill tie in the 85 power feed to the same heavy lead. I let what ever form of control ground the 86 terminal and run power from which ever terminal you need (NC=Normally closed, NO=Normally open) then to the fan(s) then good grounds either to main body grounds, like through rad support or directly back to the battery.
I usually use the adjustable fan controllers that you push through the fins at top of rad near hose or into the upper hose.
I tried keyed power for pull in of relays and just had boil over issues, my fan generally ran a few minutes after car shut off if it wasnt on when I shut down but NEVER had any issues.
Too many key controlled things complicate. I let temp sensors run my fans. And if I want an extra ability to control fan THEN add in a spare hidden switch or computer control.
I prefer the oval GM relays as they can handle 70 amp surge. Most 30 amp "square" or "Bosch" relays I am just not a fan of. Also the little 5 blade Ford relays are quite robust if kept cool.
I actually like the Ford Taurus relay/fuse box under hood or in back as it also incorporates a 175 amp max fuse you can use to feed alternator/main power lines,,,also these can be used for other add on's a several stereo companies make holder for them.
It also like my favorite what of installing terminals or splicing wires (non insulated crimp, solder, shrink tube or tape,,,never have any issues)my ways come from experience.