CK5 Network
Become a member of the largest online community for Chevy K5 Blazer, Suburban and C/K series truck owners!

Fans and thermostats

anwat

1/2 ton status
Premium Member
Joined
Apr 28, 2019
Posts
578
Reaction score
413
Location
Long Beach, CA
Setting up the cooling system on my k5, and would like some input from those more experienced than me. I spend most of my wheeling time in Death Valley/Mojave desert, so i need something for hot days crawling up a trail at 5 mph. I'm running a two row 19x35 aluminum radiator with one inch tubes. I have a shroud for the radiator which covers the entire core surface and seals tight to the radiator, the fans will be set 1.25" back from the core with half the blade in the shroud, half out. They are Maradyne 14" fans that pull 2100 cfm @ 0in static. 195 degree thermostat (oem temp) Edlebrock Victor series waterpump on a 454 with a mild cam and Fi tech injection.

I'm going to set the fans up independently so that if one fails, the other will still work, completely redundant wiring, sensors and everything. Since I'm doing it that way, I was considering putting one thermostat switch in with a 195 on setting, and the second switch with a 210 on setting, in hopes of allowing one fan to do most of the work until it really starts to get hot.

First off, is the thermostat at 195 unreasonable? I went with the OEM recommended temp, since I figure they know more than me about that. Second, is the dual "on" temp a good idea, or does it just mean the cooling system will be playing catch-up all the time? Should I just set them both at 195? Or even lower?

I'm also running a trans cooler with it's own fan and an oil cooler. Any advice or comments are welcome, I'm just trying to get as much info from out there before I cost myself money doing something stupid.
 

1977k5

1 ton status
Vendor
GMOTM Winner
Joined
May 26, 2003
Posts
10,698
Reaction score
1,140
195 is totally fine and advisable.

Having two temp targets for two fans is common both in OE and aftermarket, it's how I set my stuff up. IMO having them both at the same temp is wasteful and harder on the fans.
 

anwat

1/2 ton status
Premium Member
Joined
Apr 28, 2019
Posts
578
Reaction score
413
Location
Long Beach, CA
Do you think 195 and 210 are good setpoints to start with. Obviously, I can tweak stuff once I see how the temps are in the real world. I'm thinking maybe a 195 switch, and then one of the adjustable setting switches for the other.
 

6872xtc

make mine modified
Premium Member
GMOTM Winner
Joined
Sep 16, 2008
Posts
8,661
Solutions
1
Reaction score
9,111
Location
Palisade,Colorado
I believe that a 195 on for the first fan can be dependent upon where the switch is placed. It could possibly make the fan come on just as the thermostat opens. I personally would have to use trial and error to find out. But if the first fan comes on too late, then it may not be able to do enough before the 2nd one needs to come on to help. Just my idea, no proof.

Just as an FYI, and my limited experience, I like how my '70 big block truck does with the Edelbrock water pump and Evans waterless coolant. The low pressure in the system without fear of boiling seems to work well while the pump appears to flow the coolant well. If you look at the size of the radiator in a '67 to '72 truck, they are missing square inches compared to the tall version in the '73 and up trucks.
 

TJ1978

I have MANY questions
Premium Member
Joined
Oct 27, 2019
Posts
3,951
Reaction score
3,992
Location
East Valley, Arizona
195is good....i run 2 -14’ (i think) electric fans. Seems ok thusfar. Mine fans come at 180 but I seem to hover around 185ish..
 

bp71k5

3/4 ton status
Premium Member
Joined
Mar 31, 2006
Posts
8,721
Reaction score
2,668
Location
Knoxville, TN 37922
I set my first one to come on a little over 195, maybe 200 I think. Then the power ramps up slowly at some point over that. I have a PWM controller though.

if you set it to 195, and use a 195 thermostat, the fans will come on just as the engine finally warms up. The radiator may be able to keep it at 195 without the fans so that’s why I set it up for a little higher.
 

anwat

1/2 ton status
Premium Member
Joined
Apr 28, 2019
Posts
578
Reaction score
413
Location
Long Beach, CA
Thanks, at least I'm not too far off base in my thinking. I did consider the waterless coolant, but two things deterred me. Well, really it's only one thing: You can't have any water in the system. So, getting the coolant and water all the way out of the entire system would be a job. I'd be willing to try that, but the more concerning thing is that when I have trouble in some remote area, I can only fill that thing with waterless coolant, meaning I need to bring several gallons with me, and I can't drink it or wash up in it. Worst case, I can always use some spring water or other water-based by products of human metabolism in there if I have to.
 

anwat

1/2 ton status
Premium Member
Joined
Apr 28, 2019
Posts
578
Reaction score
413
Location
Long Beach, CA
I set my first one to come on a little over 195, maybe 200 I think. Then the power ramps up slowly at some point over that. I have a PWM controller though.

if you set it to 195, and use a 195 thermostat, the fans will come on just as the engine finally warms up. The radiator may be able to keep it at 195 without the fans so that’s why I set it up for a little higher.

That was my thinking, if I'm already moving by the time it hits 195, they may not come on at all until I slow/stop for a while. The PWM only works on the three prong fans with high/low settings, correct?
 

dyeager535

1 ton status
Premium Member
Joined
Dec 13, 2000
Posts
30,280
Solutions
1
Reaction score
1,787
Location
Germany
GM also used switches for the secondary fan in some applications. Came on at something pretty high IIRC, 240" I want to say for TPI. As I recall, back as far as the Grand Nationals they were using fan switches, there should be a variety of on\off temp switches out there.

I'd probably try and wire it up so it was easily changeable (I mean so you can test a particular setup easily without having to solid wire everything, until you get what works nailed down, then solidify the wiring). In hot conditions you very well may need to have both fans going to keep it at 195*. With a small block I've never needed the second fan, but those aren't super hot ambient conditions, and 100 cubic inches fewer.
 
Last edited:

anwat

1/2 ton status
Premium Member
Joined
Apr 28, 2019
Posts
578
Reaction score
413
Location
Long Beach, CA
GM also used switches for the secondary fan in some applications. Came on at something pretty high IIRC, 240" I want to say for TPI. As I recall, back as far as the Grand Nationals they were using fan switches, there should be a variety of on\off temp switches out there.

I'd probably try and wire it up so it was easily changeable. In hot conditions you very well may need to have both fans going to keep it at 195*. With a small block I've never needed the second fan, but those aren't super hot ambient conditions, and 100 cubic inches fewer.

I'll see what I can find out there and give it a try. This is my first big block, and I noticed it does tend to be hotter than my 350 pretty much all the time. Seems like once it passes 230-235, it's not going to cool off unless I shut it down and wait. I think it's when the trans starts getting too hot, it's just too much for the radiator to cool everything down. The new fans may help, and I've been trying to keep the torque converter locked up more when the trail allows. I had a radiator from a diesel suburban in the small block truck...if it got hot, I could just let it idle and it would cool off.
 

bp71k5

3/4 ton status
Premium Member
Joined
Mar 31, 2006
Posts
8,721
Reaction score
2,668
Location
Knoxville, TN 37922
That was my thinking, if I'm already moving by the time it hits 195, they may not come on at all until I slow/stop for a while. The PWM only works on the three prong fans with high/low settings, correct?

You can get a PWM controller that works with 2 wire fans, that’s what I’m using. A switch setup may be just as good and if that’s what you have, would make sense to try out. I’m using it on my 454 and the fans cycle on and off at idle every few minutes. On the freeway, I don’t hear them come on very often. I can see when they turn on cause the voltmeter dips a bit. If you’re in the desert, conditions might keep the fans on more often.
I’d just make sure the fans actually do cycle at idle or turn off when air is already moving through the radiator on its own. If they never turn off, something isn’t working the way it should.
 

anwat

1/2 ton status
Premium Member
Joined
Apr 28, 2019
Posts
578
Reaction score
413
Location
Long Beach, CA
That's what I'm going to do. I found a good controller, I'm going to run that on one and the switch setup on the second fan, with it set at 210 for starters. The PWM controller is adjustable and simple as can be...dccontrols.com, and like you said will work with a two wire fan. I also hooked up a light on the dash so I know when the fans are running...I learned the hard way what happens to your A/C when the fans aren't working and it's on...cost me the same as the fan controller, so I figure it's a good investment. Thanks for the input...I'll post up a couple of photos and an update when it's done later in the week.
 

dyeager535

1 ton status
Premium Member
Joined
Dec 13, 2000
Posts
30,280
Solutions
1
Reaction score
1,787
Location
Germany
Another consideration, just to put it out there, is what alternator you run.

I've got a CS110, and it has zero issue keeping voltage up with about as heavy a load as I can put on it. I've never tested when all accessories were on, AND the fan came on, but I do know that voltage dips slightly when the fan first starts. However, that is the extent of it. Never had an issue where the alternator couldn't keep up with the load. If you don't have a pretty stout alternator, I can see one of the old 12SI units that wasn't rated very high, having issues. One benefit of having staggered fan startup (if dual fans, and/or not PWM) is that you aren't subjecting the system to the startup load of both fans.

Most will say if upgrading go whole hog and go with the CS144. There are a number of aftermarket builders out there too that have good products.
 

anwat

1/2 ton status
Premium Member
Joined
Apr 28, 2019
Posts
578
Reaction score
413
Location
Long Beach, CA
I have the CS144, and have everything wired to a bus bar as recommended by MAD electric. Since you bring the topic up, though, I'm a little confused on the dual battery wiring. As it stands now, I'm running two parallel Odyssey Extreme batteries, no isolator. I have them connected by 0 ga cable. I have the 10 ga charging wire from the distribution block running to one of the batteries. Will that suffice, or should I run a second charging wire from the block to the other battery also? I've got a 2 ga from the alternator to the distribution block. I'm just headed out to finish up the wiring on the fans now. Then I'm going to get a fire extinguisher, and start that puppy up and see what happens.
 

imiceman44

Hoarder extraordinaire
Premium Member
Joined
Aug 5, 2002
Posts
25,848
Reaction score
9,822
Location
Lincoln, CA
I have the CS144, and have everything wired to a bus bar as recommended by MAD electric. Since you bring the topic up, though, I'm a little confused on the dual battery wiring. As it stands now, I'm running two parallel Odyssey Extreme batteries, no isolator. I have them connected by 0 ga cable. I have the 10 ga charging wire from the distribution block running to one of the batteries. Will that suffice, or should I run a second charging wire from the block to the other battery also? I've got a 2 ga from the alternator to the distribution block. I'm just headed out to finish up the wiring on the fans now. Then I'm going to get a fire extinguisher, and start that puppy up and see what happens.
The 0 gauge wire between the batteries is better than the other 10 gauge you want to add.
I personally would use a 6 or 4 for the charging wire but 10 is probably the stock size so it should be enough
 

anwat

1/2 ton status
Premium Member
Joined
Apr 28, 2019
Posts
578
Reaction score
413
Location
Long Beach, CA
I am using a 2 from the alternator to the distribution block, the 10 is only there for the trip from the block to the battery to slow the charge down a little and prolong the life of the battery. The sensor wire is going to the block, not the battery.
 

bp71k5

3/4 ton status
Premium Member
Joined
Mar 31, 2006
Posts
8,721
Reaction score
2,668
Location
Knoxville, TN 37922
I am using a 2 from the alternator to the distribution block, the 10 is only there for the trip from the block to the battery to slow the charge down a little and prolong the life of the battery. The sensor wire is going to the block, not the battery.

sounds like you’ve read the MAD electrical site. I used the same idea and it’s worked well.
 

anwat

1/2 ton status
Premium Member
Joined
Apr 28, 2019
Posts
578
Reaction score
413
Location
Long Beach, CA
sounds like you’ve read the MAD electrical site. I used the same idea and it’s worked well.
Are you running a dual battery setup? If so, do you have a seperate charging wire going to the other battery, or just a wire to the first? My small knowledge of electrical tells me it shouldn't matter which way, they will both get charged/drained at the same rate if they are wired parallel. And yes, credit goes to MAD electrical. Great info!
 

bp71k5

3/4 ton status
Premium Member
Joined
Mar 31, 2006
Posts
8,721
Reaction score
2,668
Location
Knoxville, TN 37922
Are you running a dual battery setup? If so, do you have a seperate charging wire going to the other battery, or just a wire to the first? My small knowledge of electrical tells me it shouldn't matter which way, they will both get charged/drained at the same rate if they are wired parallel. And yes, credit goes to MAD electrical. Great info!

I don’t, but I think I read that it’s not a great idea to charge both batteries at the same time. Something about the potential to overcharge one of them as they wear out at different rates. I’m not informed about dual batteries though, so you’ll need some other help.
 

imiceman44

Hoarder extraordinaire
Premium Member
Joined
Aug 5, 2002
Posts
25,848
Reaction score
9,822
Location
Lincoln, CA
I don’t, but I think I read that it’s not a great idea to charge both batteries at the same time. Something about the potential to overcharge one of them as they wear out at different rates. I’m not informed about dual batteries though, so you’ll need some other help.
When 2 batteries are in parallel mode with a big enough cable they are as one.
That's why you need to have them same size and age.
If you have them separate and use an isolator then you can have whatever and yes they will discharge at different rates
 
Top Bottom