Franko

I have a new Champion radiator and Mark VIII fan to go on truck. The relay kit I got from Champion is only a 4 post 30/40 amp and I've been told I need a 80 because the fan hits 70-75 amps at start up. I can only find a 5 post 80 on ebay and have checked in my area at a couple of places and they don't have them. My relay receiver is only 4 post. Will the 5 post 80 work? I understand the 5th post would be to have both high and low hooked up. I'm not up on electrical that much. I guess I could add a 5th wire to receiver or will it work if I just hook up one of the speeds. I want to run fan off the heat sensor that goes into heat sending unit. Give me a little explanation please and also what is the best brand relay to use and where locally can I get the 80 amp relay. If I can get photo to post, this shows what I have. Wouldn't work. Got upload error which I've gotten before.

fltdriver

For high/low operation you need two relays, one for high power, one for power to low.

The middle prong (87a) is constant power without signal from switch, 87 is power only with signal from switch (86). 30 is power in and 85 is ground. Both my high and low relays are 5 prong 30/40 with the middle prong (87a) left unused. You are better off leaving that terminal in the harness without a lead wire, if you put a wire in you will just have to cap it off.

A 30/40 is sufficient to power that fan on low, for high you have two options, get a 80 amp relay or wire two 40 amp relays in parallel to provide adequate power for spikes. On some of the mustang forums guys using those fans do both 80 amp or two 40s with 60 amp fuse.

Franko

I've thought of just wiring it for low. My temp gauge hardly ever gets past o on normal, but that is the factory gauge. I've read some have an in cab switch and so on. Where does the 60 amp fuse go? Thanks fltdr for the reply.

fltdriver

I have mine set up with temp controller kicking the high speed on and a manual switch for low. It's also hooked up so if the AC gets turned on the high speed kicks in.

30>fuse>battery +
85>body ground
86>signal in
87>fan
87a>not used

You won't need a 60 amp fuse if you are just using one 30/40 relay, get a 30 or 40 amp inline fuse, place it within 1-1.5ft of the battery (usually don't want more than 18" from battery to an inline fuse). If you get this controller from auto zone then you can hook it up to 86 so the low will be turned on when it hits a certain temp, you can also run a manual switch to 86 so the fan can also be turned on at your discretion.

I have my temp set to ~185* and it hardly ever kicks on, in fact I rarely turn the fan on manually either unless the truck is sitting and running after it's up to operating temp.

Franko

Appreciate the info. I've wondered about my factory temp gauge, but when I turn heat off, it will move up about a hands width. I'll go back over your post and maybe get it done next weekend, but I have doubts. Much needed info though. Thanks again.

Franko

I'm returning to this post because part of this goes with wiring up elec. fan. First my temp gauge is reading over half of normal. That is what it will read starting stone cold. Don't think it is that hot at night here in Bama. I assume for now it is the sending unit. I almost put my new radiator and fan on today, but was first stumped thinking ECT was sender. Now I have this question. How do I wire up a thermo switch and still have factory temp gauge working. I did find sending unit about half way from front of engine on drivers side of intake. Two wires come from unit, orange and black. Also what size is sending unit thread area? My thermo switch is 5/8's across threads. and has 1 male prong from top. It is a 185 degree. Just put in new thermostat this morning and ran some flush through it. Speaking of the fuse mentioned above, the wiring kit came with a 30 amp short stop. I think I'm ready except for sending unit info.

fltdriver

What you found was the ECT sensor, that is for the ECU. The ECT sender has only one wire and is what the dash gauge uses. Not sure how you will need to set that up for the dash gauge to work, the temp sensor I used was external and mounts to the radiator.

Franko

I had printed off thread for reference and missed the highlighted part that went to Autozone for cooling fan control which is external. I am picking that up today and plan on sat to put every thing in.

fltdriver

If I were you I would consider replacing the ECT sender, if it's reading at the half mark on start up it's probably toast. Another option, since it's not currently functioning properly, would be to install an actual temp gauge instead of the dummy switch that is in the cluster. Just a thought.

Franko

I agree. Got everything installed, and all is working fine. Did a final ck this morning on a warm up from cold start and fan is working fine. I need to tweek the thermo stat control but I believe it is close. Radiator was almost to hot to touch when fan came. I noticed rad gets hotter than top hose in the beginning. I need a pup thermometer to ck rad temp. I have the temp sensor probe pushed between vanes. All connections are strong and heat shrink on all. I had almost a new pack of wire loom I've had for over 12 years. Came in handy. The first thing I noticed was the lack of noise. Does anyone know what the HP gain is for removing the metal fan? I guess 1-2. Will also wonder on mpg. Every little bit helps.