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Electric Fans

cabledawg

cabledawg

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I'm switching from mech to elec fans. I wanted to know what setup folks use. I was thinking one on a thermostat and the other on a manual switch. THe thermostat controlled fan would have constant power so it can run after the engine is off. What's your take on this setup?

FYI these fans are rated at 2500 cfm each and draw about 8-12 amps each. The thermostat relay is rated for 30 amps.
 
The ultimate fan is a mark VIII from a lincoln car, they move 4500CFM and can be found on ebay. I use one in my street/strip car, awesome.
 
Windstars are your easiest bet...they've been done to death here, they work, and they fit. Lots of people to offer info.

As to running after the car is shut off...I don't like it. The possibility of it coming on when fingers are in the wrong place is too great. If you are injected, you don't need to worry about heat soak, so there is absolutely no benefit to running them after the engine is shut off.

Both on relays, both controlled by two temp switches. Both on with AC, primary that gets you down to about 10* OVER rated thermostat temp without, secondary with AC and for a higher "emergency" fan. Both with manual override, if you need it for crossing creeks. Otherwise, the manual override adds unnecessary complexity.

I suspect if wired correctly, you could use the same relays/connectors, which would give you redundancy, meaning you wouldn't need spare parts to get you out if something failed. My two GM fans, out of an LT or LS1, are completely redundant, every plug and relay will interchange, easily.
 
I've already got the fans and they are generic setup. I dont have a traditional AC setup. My stock stuff never worked very well and even with rear AC, the kids would sweat to death on road trips. So I'm installing a low profile RV rooftop unit (only 7" high) and an inverter to run it.

Good point on the run after off setup. I dont really need it and I certainly dont want to kill the battery or get caught in it if the thermostat malfunctions. I'm not crossing creeks but this truck has a hard time getting warm in the winter, so I do want to have the ability to turn both fans off so the engine can reach a higher temp for heat.

Thanks for the info. I'll keep digging in the search box. Never know, someone might have some trick setup that got forgotten that works real slick.:D
 
You could use a fan controller, most are programmed to run the fans for a period of time after motor shutdown and they ease the load on the alt. on startup too.
 
If the fans are on thermostats, and the engine thermostat works right, they have no bearing on the engine getting/staying warm. Assuming that's what you were getting at. :)

Even running all the time (bad idea) fans SHOULD have no bearing on engine operating temperature, as the radiator can be ice cold, that coolant will just sit there, until the coolant in the block gets up to thermostat operating temp.
 
I have a 160 thermostat in the engine so it stays cool in the summer, but I dont feel like swapping for a higher temp inthe winter. I also dont feel like changing the fan thermostat for winter/summer temps. The 'stat I ordered for the fan kicks on at 180 and off at 170 so by manually shutting off the fan, I'm hoping the engine will warm up faster. I just installed a block heater and that helped alot (reaches roughly 100 with the truck inthe garage and the space heater running) but I've resorted to using cardboard to block the radiator until the engine gets warm.
 
Yeah, you aren't going to speed up the heating of an engine by turning the fans off...the thermostat is the only thing that "retains" heat in the motor. Even with a stock clutch fan. Essentially you are getting no coolant flow until the thermostat reaches rated temp, so no heat is being "lost" through the radiator regardless if a fan is pulling air through it or not.

You'd end up working the electrical system harder than necessary by using the fan to attempt to regulate engine operating temp. It would have been easier to stick with a higher temp t-stat, but you'd likewise over burden the electrical system with your new fan switch which is/would be under a higher temp rated t-stat.

A lower temp t-stat is a bandaid for an ineffective cooling system, your fan setup may or may not solve that...
 
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The truck never overheated to start with. When I put in a new engine two years ago, I wanted to make sure the temps stayed down in the summer as this was our family travel rig (now tow rig). The reason I had to replace the engine was because the sandwich adapter for the oil cooler blew apart and I almost siezed the engine. Since I thought at the time the rear engine seal had gone, I just replaced the engine. So the new engine doesnt have an oil cooler.
So to keep the engine cooler in the summer when it is most likely to be running hard, I used a lower temp thermostat. The cooling system works awesome and although the radiator is old, the tubes are fairly open still and has good flow. I just didnt know that using a low temp stat would make it harder to warm up in winter.

By shutting the fans off, I'm hoping that the stop of airflow will allow the coolant to heat up a little more. I understand that until the stat opens, the coolant just moves in the block. In fact, I think there are times when it doesnt open at all cuz the temp gauge will only show a hair above 100 after driving around town. This is why I resorted to using cardboard in front of the radiator.
 
A thermostat has absolutely no bearing on how long it takes an engine to heat up, unless it's faulty or missing. A 250* thermostat would get to 160* just as fast as a 160* thermostat. Only difference is what temp the thermostat finally opens. It should NOT be opened at all when the engine is under operating temp, which is why fans have no bearing on how long an engine takes to heat up, with a properly operating thermostat.

What fan(s) are in there now? Even the clutch fan doesn't move air when the truck is below operating temp...
 
What are the outside temps when you need to use the cardboard?

Up here we HAVE to use cardboard or something to reduce airflow for the motor to warm up during the winter months.
 
I personally don't like manual fan controls. It only takes one moment of inattention to overheat the motor.

I just put electric fans in. I used the SPAL fan controller with an independent temperature sending unit.

As already stated, there is no benefit to run the fans after turning the engine off. You are cooling the radiator which is not circulating anything. The steel block will not dissipate any appreciable heat be running the fans after ignition off.
 
Anything under 40 and the cardboard goes in. Sometimes just to warm everything up then I'll fold it in half and just block one side. But when its staying under 30 all day, it blocks the whole radiator the whole time.
My fan clutch might be f***ed up cuz it still moves a ton of air even on initial startup.
I'm understanding the point of coolant flow before and after the stat opens. What I'm trying to say is that once the stat opens at 160 deg, I want to be able to leave the fans off so the engine will continue to heat up. Otherwise, the fans would start cooling the warm coolant and therefore the engine would never get any hotter. However in the summer time, when temps down here can reach 100+, adding the towing duty this truck sees in the summer, I want to make sure the engine temps stay down, so I built the cooling system to be very efficient. High flow pump and lower temp thermostat helps the engine stay cooler in hot weather, but it also prevents it from ever getting real warm in the winter.

So here is my next question: I learned I need to use relays to run the fans, but how are you guys hooking up the ignition switched power? Is the main feed tapped into constant power and then the switch feed on the ign power? Or are both on the ign power and if so, where is it connected to? Additionally, what relays are being used (I might be able to find this in the search, now that I know what to search for)?
 
On my truck, I've been down to 16* with no restrictions. That's nothing compared to the guys in the cold areas, but it's indicative.

You are begging for trouble by trying to control engine temp with the fans. The fans aren't made to be on all the time, they draw a lot of juice, and if something fails (inattention or a switch) your motor will be toast.

I suppose it's too late, you've already ordered the parts, but the answer to me is to get a 195* thermostat, and if your cooling system is up to par (which it sounds like you've gone to pains to make sure of) you will have absolutely NO problems, regardless of the outside temperature. That's the way GM set up all their trucks and cars from the factory, and very few have any sorts of overheating or under-heating problems. It's unknown what the stock clutch fan moves, but it has to be a relatively huge amount, as many aftermarket electric fan setups can't keep up with it. Again, an efficient radiator and water pump will help "crutch" an inefficient fan, but a good fan is yet another margin of error as your cooling system ages, or the ambient temp skyrockets.

A lower temp thermostat does not help an engine stay cooler under load. What a lower temp thermostat does is provide a "cushion" for overheating, but if the load is too great for the cooling system, if it overheats at 195*, it will certainly overheat at 160*. If you decide 250* is overheating for your motor, you would just have 35* "extra" before you reach what a 195* thermostat would already be running. If your cooling system is in good shape, typically removing the thermostat means the engine NEVER heats up...the thermostat simply puts the engine where GM figured it ran best, and the cooling systems job is to get it to that temperature, and keep it there.

With injection you are introducing a whole host of other problems, such as the engine never "unchoking" itself, and the O2 sensor not working right, both of which are bad for the motor and bad for gas mileage.

I use the stock oval topped GM relays that were common in the late 80's-90's. Free from the wrecking yards and available everywhere. Weatherpack connectors. I doubt they are good to anything more than 30A surge.

The later trucks fuse panels have a whole bunch of empty accessory slots along the top edges, find the ones that are ignition switched, and use those. The actual fan power goes from the battery, through the relay, to the fans. Use a junction block to feed that power. I grabbed something off of a late 80's early 90's Cadillac, others have pulled entire "panels" from GM vehicles of the same vintage, which include both fuses and relays. In my case my aftermarket + battery cable has one fairly large spare lead hanging off of it, I ran that to a junction block next to the headlight buckets, and mounted my relays to the metal fan holding frame I came up with, so the relays and junction block took little wire to run.
 
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So I've shot myself in the foot by running such a low temp stat. Thermostats are cheap, so I'll go ahead and get another one to put in there. As for the fans, I'll put both on thermostats, but keep one ona higher temp stat to kick in when things get hot and let the other do its thing for normal operating temps.:D

Thanks for the info on the relays. I'll see what I can scrounge up but JY chevy parts are hard to come by here in Wichita. Apparently most GM's are still peoples backyards and not the wrecking yards:p:. I'm already on the hunt for another fuse panel due to all the extra electronics inthis truck and I want the main stuff seperated from the added junk (kids gotta stay happy on long trips:rolleyes:) I've already dipped my fingers inthe alternator threads to charge the dual batt setup I've got now.
 
Sounds like a plan. :)

Just make sure that your fan temp switches are for higher than the rated temp of the thermostat. GM had quite a gap, something like 230* on a TPI small block, with of course a 195* thermostat. I don't quite like that spread, mine comes on at 215* and off at 205*. If I was in a hotter climate I might want to let it get hotter just so the fans didn't cycle so much.
 
Like I said, I might just use two different temp thermostats for the fans. One at like 215 on and 200 off and the other at 220 on and 210 off so that if for some reason the engine is having a hard time cooling (like when I hit the passes) the second fan will kick in to help with cooling duty.:D
 
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