A couple of photos from my "another cheap electric fan build"

[68 IRON]

Yeller, I was wondering if you could check the amp draw at fan start up. Do you see dimming of lights when the fan comes on? And these alternators are rated at about 60 amps?(stock 68 c10, straight 6) Seems kinda high, doesnt it? Just dont want to get in over my head.....I hate dealing with electricity (what I dont know). And yes I'm mulling over your offer.

[Old Yeller 1970]

I'll see what I can do about checking the amp draw at start up. According to the guy who did the original conversion they pull 12 amps while running. My alternator is supposed to be a 60 amp unit. That's about half, or less, what a modern alternator puts out but it's only running the spark plugs and a puny radio during the day.

[68GMCCustom]

....and those older alt's don't put out that much at idle.

[kevmic28]

I havent noticed the lights dimming at all. I bought a infrared temp sensor and realized that my gauge is bad. With the sensor after the engine running for 20 minutes the intake had a temp of 186. After I ran into town, 20 minute drive, the temp was up the 204 on the heads and the intake.
The fan is blowing so hard that there was a 100 degree temp difference between the tube on the front and the rear of my Hooker headers at idle.

[Old Yeller 1970]

Get this. My 30 amp breaker failed. It must have happened the first day I drove it because I noticed the truck ran hot at the end of the day when I had to make a stop in town. I got the rebuilt PS gear box on it today and took it out for a spin. When I got back to the garage I noticed the fan wasn't running. After some trouble shooting I found the breaker defective. I called Jegs tonight and they're sending me another one Monday. Give Jegs a thumbs up for customer service.

Concerning testing the amp draw I'm going to have to buy a cheap clamp on meter that will test DC.

[kevmic28]

Yeah my breaker from Jegs was junk too. I went and got one from advanced auto for 3.50. Works just fine and even picked up and extra just in case. Also I ended up hard wiring a switch into the cab so I could have the fan on at start up and not wait till the engine heated up for the senssor to kick on.
I pulled a small trailer today with a couple dirtbikes to the next town over. about 40 mile trip and it ran about 200 the whole way and 205 back in 93 degree weather.

[DBear]

if i was to use this set up with the dodge fan...what shroud does it fit??? Is there a stock shroud it would fit?

[Old Yeller 1970]

Follow this link 'cause you're in luck. This all got started because the fan fits perfectly inside a stock 67-72 fan shroud.

[71meangreenc10]

I have my jeep fan in and with lights on, fan running I am pulling about 25 amps with a Amp Clamp on the Alt wires.....Stock Alt.

I also used a better kit for the fan realy that you can get from summit/jegs that turns the fans on @ 60% so the spike isnt that hard on the system.

http://www.summitracing.com/parts/FLX-31165/

Smitty

[Old Yeller 1970]

If it's pulling a steady load of 25 amps I can see why the 30 amp breaker didn't last long. Jegs did send a replacement but I think I'll get a 40.

Edit: I just realized that's 25 with the lights on. Still a 40 amp breaker might be in order.

[nightmare]

quick question on this installation. I don't have a square head drive small enough to get the plug out of the head. I'm thinking about having the fan on only when the truck is on. Will it hurt the fan if it runs the entire time the truck is on?

[kevmic28]

I run mine all the time but I do have a switch wired up to it so I can turn it on and off at start up. So I switch it on after I start it so that Im not drawing that much energy at startup.
I just cut off the plug and wired in a couple quick disconnect connectors.

[MagmaJct]

Not sure how power steering brackets took over the thread, oh well.

I have the stock fan, but have looked into a replacement electric fan. I would have to suggest that the thermostat be installed coupled to the radiator, not the engine. Here's my logic:

The idea of controlling the fan is to have it run when it's needed, and have it shut off when it's not. The radiator needs air to flow through it for it to cool the water. When driving at speed ram air does the job without the fan needing to be on. This is where HP and fuel savings are realized.

At low speed or idle, very little to no air flows through the radiator. The fan solves this problem. If the thermostat is installed in the engine, the fan will come on with engine heat. Meaning, at high speed driving when more HP is being produced, so will more heat, the fan will come on. BUT, the fan is not needed at high speed, because ram air is sufficient.

The original fan clutch was sensitive to radiator heat more so than engine heat by the fact of its placement. At low speed/idle the clutch was surrounded by air heated from the radiator causing it to slip less. As vehicle speed increased so did the air flow thus cooling the radiator and the air around it, the clutch would slip more.

Want more HP and improved gas mileage? Use a sensor in the radiator. While it's true I've never run an electric fan on my truck, just thinking about the problem give me the answer.

[Classic Heartbeat]

I was wondering if you could check the amp draw at fan start up. Do you see dimming of lights when the fan comes on? And these alternators are rated at about 60 amps?(stock 68 c10, straight 6) Seems kinda high, doesnt it? Just dont want to get in over my head.....I hate dealing with electricity (what I dont know).

The stock alternator for non A/C trucks is 45 amp. WES

[kevmic28]

Problem I see with having the sensor on the radiator is that this. Using a infrared temp sensor I have noticed that the radiator has different temps depending on where you scan it. If you wait till the radiator hits 180 degrees or so the engine will be way hotter than that. The water running through the hose to the radiator starts the cooling effect.
Heres my resoning from my truck. Scan the heads they are at 190 degrees. Scan the radiator hose and its at say 175 to 180 degrees. Scan the radiator at the entry point and its 160 to 175 and drops to down from there as I scan across the radiator. So depending on where you put the sensor on the radiator sitting in stop and go traffic Im guessing the the engine temp would be somewhere between 240 and 260 to get the sensor to turn on the fan.
I mounted my sensor on top of the theromstat, in its housing. Once the thermostat his it temp and opens it hits the sensor and turns on the fan at 185. But I also have my fan hard wirded in the cab to a switch so I can just turn it on after I start the truck. That way its just always on. No probelms of over heating at all now.
If I can just fix my temp gage so it doesnt read at the top of the cool range Ill be good.

[Classic Heartbeat]

To speak to installing the fans thermostat anywhere but in the radiator renders the thermostat innefective. The water that the fans cool is in the radiator, not anywhere else. So placing the censor anywhere else doesn't make sence to me. It would seem to me that the censor in the water neck would result in the fans running longer than necessary, because of the heat from the engine. If you want the fans to run longer to cool the water more, just set the temp setting lower. WES

[kevmic28]

Well the reason Im running mine in the water neck was because I could not get the plug out of the head on my engine. I tried everything I could think of but no dice. So this was the only other option.

[Classic Heartbeat]

I believe that the water neck is better than the head, but not mutch. Installing one in the engine anywhere just isn't going to cool the water the why the fans are designed to cool. It musr be more about asthetics than utillity. Turning the fans on and off by hand would be just as effective, or just have them run all the time. WES

[Old Yeller 1970]

Originally Posted by Classic Heartbeat

The real test to a cooling systom is not while driving down the road where you have ambiant air forced through the radiator witch asists in cooling, but just sitting in traffic idleing. Then the fans have to do all the work. That is where the temprature sensor in the head will be innefective. WES

OK, finally got Old Yeller's new recovery tank installed and the failed 30 Amp fan breaker replaced and took the truck out for a spin this afternoon. When I noticed we were sitting at 106 degrees today, I figured this was as good a test as one can get.

I did a number of high speeds, slow speeds, starts and stops, and sitting and idling and the short answer is the cooling system performed great.

I drove about 2 1/2 miles down the road from a cold start. In the last 1/2 mile of the 2 1/2 miles, I noticed that the temperature gauge moved past 185 degrees (my thermostat rating) but was less than half way across. I figure that was when the thermostat was opening and would guess the temperature to have momentarily gone up to 195-200 degrees. That was right when I slowed down to turn around. I cut the truck off and verified that the fan was already running. By the time I turned around the gauge was sitting at the 185 mark. I drove about 90MPH for 2 miles and then slowed to a crawl for a 1/4 mile like city traffic and the gauge didn't move. I drove 4 more miles and stopped again and sat for a minute and the gauge didn't move. I drove back to the house at speeds between 70 and 90 MPH, crawled forward and and sat for a while longer and the gauge didn't move. When I cut the engine off I could hear that the fan had been running.

I've had enough experience with Old Yeller to know that if the fan isn't running or the system isn't properly cooling, coming to a stop will cause the engine temperature to begin rising immediately but that never happened. With the ambient temperature well over 100 degrees and, after warm up, a consistent engine temp of 185 at all speeds including no speed, I'm going to declare this a success and say that the temp sensor in the head is effective.

[68 IRON]

I forgot to check back and get your report Yeller! With all the info here I think this is a no brainer. Listening to my son's engine spin that big fan (and the I6 turning that little bitty thing) I see more advantage than disadvantage.