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Electric Fan clutch

I eliminated the tee. The adapter I cannot eliminate as the probe is actually long enough to go to the bottom of the thermostat housing even with the adapter in place.

Yesterday's drive to the gym and back (my debugging trip) was MUCH better. The disengagement was still longer than I'd like but MUCH better than with the tee there. My max temp yesterday was only 201 so I have a bit of headroom on the engagement screw, so I went ahead and bumped it up a smidgen and will test today.

As for the fan - the Dmax fan is significantly heavier than the OEM H1 fan. A PWM system works by modulating the ground/earth side of the circuit so that its getting 12V+ but intermittently, like someone is tapping on an old school morse code telegraph machine. With the mishimoto I don't think that it was getting enough juice at the lower engagement temp, but with the flex-a-lite I can definitely tell with my throttle response when its barely engaged - especially on the cooldown.

The Flex-a-lite has a manual override switch as well that locks it up 100% - I'll see if I can figure out a way to measure its cool down. I also have the switch in the cab wired up to completely shut down the controller so I could measure how long the clutch stays engaged with absolutely no power whatsoever being applied.

(long slopes in the middle were while the truck was parked)
1720788747109.png
 
Something too, if you have AC on your Humve. is there room for an electric fan in front of the condenser? and does the controller have a provision for dual fans. say have the first one for the electric also for the AC, then the fan clutch for when you really need max cooling. this might save you some MPG's if your just putting around at low speeds not giving it a work out the electric fan in the front should keep the AC happy and push enough through to keep the engine happy then when doing off road stuff or heavy footing it, the fan clutch can do it's thing!

The electric fan doesn't need to cover the entire condenser, just half, this way it's not "blocking" too much for highway cruising so it stays happy with not needing ether fan running.
 
dbrannon79 said:
Something too, if you have AC on your Humve. is there room for an electric fan in front of the condenser? and does the controller have a provision for dual fans. say have the first one for the electric also for the AC, then the fan clutch for when you really need max cooling. this might save you some MPG's if your just putting around at low speeds not giving it a work out the electric fan in the front should keep the AC happy and push enough through to keep the engine happy then when doing off road stuff or heavy footing it, the fan clutch can do it's thing!

The electric fan doesn't need to cover the entire condenser, just half, this way it's not "blocking" too much for highway cruising so it stays happy with not needing ether fan running.
Click to expand...
As @Will L. can attest, the H1 actually suffers from the addition of electric fans. Since our issue isn't with staying cool at idle but rather staying cool at speed. The electric fans actually impede airflow that the mechanical fan would draw. The only time the electrical fans are beneficial in the H1 is when you're predominantly driving in stop-and-go-city hot driving. However, this controller fixes that problem by engaging the fan based off of a trinary switch on the A/C Dryer. When the pressure starts building in the condenser, the controller will engage the fan clutch.
 
CursedH1 said:
As @Will L. can attest, the H1 actually suffers from the addition of electric fans. Since our issue isn't with staying cool at idle but rather staying cool at speed. The electric fans actually impede airflow that the mechanical fan would draw. The only time the electrical fans are beneficial in the H1 is when you're predominantly driving in stop-and-go-city hot driving. However, this controller fixes that problem by engaging the fan based off of a trinary switch on the A/C Dryer. When the pressure starts building in the condenser, the controller will engage the fan clutch.
Click to expand...
Yeah your right, I was thinking more in the pickup world and not in the Hummers. although an H1 is something I would love to acquire one day!
 
@dbrannon79 confirming that electric fans has impeded more than one hummer at highway speed. I’ve helped guys and ones who really wanted to keep the already added electric fans, I got them to do other cooling improvements and they saw improvements enough where they trusted my judgment enough to do a test run recording temps, remove the fan “temporarily” and retest. Once proved it hinders the cooling by slowing the allowed volume of air across the radiator- they learn to leave it off.
There are some people who make enough improvements in other areas that it can handle the obstruction and helps them with the a/c and don’t suffer from the added obstruction when running a mechanical fan clutch. Usually the environment they are operating in is the biggest factor.

I had guys that live in other parts of the country (a couple from other countries) that bring their hummers to Vegas on adventure trips through the desert and spend a few days in vegas seeing the shows and such or touring the Hoover dam.
When I tell them the areas of road to pay attention to the heat- many report back seeing the highest temps ever seen on their rig. It isn’t that the roads are the steepest and longest- it is that with the lowest humidity in the country the cooling stacks simply can not shed heat as fast. I have had days where one day was 108 and 4% humidity and my truck would run at the max temperature I allow it via my right foot on the hiway. The temps in the week building to that day were all over 100 easily. The next day a storm rolls in and temps will be say 102/103 but humidity goes up to 35% and I can run my hummer 15 mph faster and still not be as hot as the day of 108 & 4%.


As to getting a hummer/hmmwv- if you or anyone has ever considered buying one- first check your dmv if they allow it to be registered as an on road vehicle.

Right now there is a member here (@Hummer H1) who is effectively buying himself a fleet of them. Dude helps everyone he can. Idk the cost of towing one from California to your state- but he is buying units with only a couple thousand miles on it for way under $10k. Optimizer engine, turbo, db2, 4L80e, all the latest and greatest like brembo (iirc) brakes, improved steering and suspension system, on and on.

Cali for example doesn’t but there are people who have done it. Nevada where I live has locked it down solid. So that is the only reason I never put a shiny paintjob and flashy wheels on my 95 hummer and sold it for top dollar- to then buy a hmmwv and add the sound deadening, comfy seats, 12v electrical system, and all the fancies- then there is enough money left over to buy a second one, fix it up part way and sell for profit- or just simply pocket the extra cash.

Any of you diy guys that has an old running 6.5 with a lot of miles who wants a new optimizer- you can buy this, swap the two engines, then turn around and sell the hmmwv for 0 loss. Look up what hmmwvs sell for in the open market in your area to make sure. And be honest telling people the engine under the hood is a tired old engine from a pickup- or the engine you took out is in your pickup you and are selling it as a project for others to drop in a dmax-without any engine at all.

I get about the worst mpg of any hummer driver I know of. I literally leave stop lights with my foot on the floor every time. Get to the posted speed limit then lift my foot. My hummer outweighs every other hummer I have compared to. Although mine was originally an open top (aka soft top or convertible) I built a ridiculously heavy (over one ton seriously) roof structure and cage/roof rack. When loaded with my tools and spare parts for zombie day - which is how I drive it 99% of the time It weighs 10,100lbs. The 2 door pickup version or 4 door pickup version with normal metal roof weighs in at roughly 7,000lbs iirc.

I get 10.5 mpg how I drive. Same mpg I had driving the same way without a turbo. Now it’s with turbo and fuel screw cranked up. Puff-o-smoke at the stopsign. Just faster 0-60 now. One time I drove at the old rate of acceleration I used to when driving wot without a turbo to compare mog before and after. I got 12.5 mpg. I have no idea what mpg it could get if I drove it normal.

I keep the 37x12.50x16.5 military mud tires on mine with the runflat/bead locks.
I never noticed a difference in mpg but consider how I drive- other guys on hummer forum say by going to aluminum wheels and tires without runflats they gain 2mpg. Eric just said the other day he gets 1.5-2 mpg more by keeping same tires as mine at 45psi but I run mine at 30. Same tires and runflats btw.
I know one guy who took a set of aluminum rims from his 99 3500 srw truck when he bought different ones for it- put those rims and 35.5” high normal pickup width tires on his hmmwv. He only uses an old tablet as his gauge set btw so gps speedometer and mileage. He said he gets 15.5 mpg. The shorter wheels gives him a little quicker acceleration but he drives mellow - I call him grandma.

I taught him how to do black diesel. Remember db2. He runs 25% gas because he found a source of free used atf and occasionally uses engine oil mixed in. So his cost after the first 900 gallons got him broke even, is equivalent to him working one Saturday every third month to get and make his fuel, and like getting 62 mpg at gasoline prices. Buying a hmmwv as his daily driver saves him a chunk of cash compared to his old ford pickup he used to drive.

It is easier to find a good used hmmwv with under 10,000 miles - than it is to find a 6.5 pickup with under 150,000 miles. And the purchase prices are similar.
The only question is - does your dmv allow it, and if fuel cost is a concern are you willing to work for a few day in the beginning then work one day every other month to get fuel costs cut by 1/3.
How much your wife yells at you- that I can’t help with. My wife found my hummer for sale when we bought it and I didn’t even know we were going to look at it.

If you find a db2 6.5 pickup- obviously can do same thing for fuel. If your dmv allows db2 conversion (mine wrecks it via smog test examination yearly) you can do the same.

If you want a dedicated off road only toy- you have to be into offroading slow. But now is the time to get smokin deals in them. Another year or so and these all might be gone. If you want fast buy a side by side.
 
So an update I replaced my fan clutch because of the long delay to engage, 5-20 minutes. At first everything seemed normal. Then made a trip to Seward to pickup a truck for my son, not so good. Even leaving the override switch on the clutch wouldn't work. Tried swapping the relay but no go, finally resorted to bypassing the controller and that worked. So I probably replaced the fan clutch for no reason. I did a bunch of online research to see if there might be a better controller but came to the conclusion that they all sucked. So I finally ordered another derale just for the ease of swapping. The consensus for most was underhood heat kills them. Maybe in the future I'll move it to the cab. But for now......
20240722_175452.jpg
You can see the black goo on the one terminal, I had already wiped the others off.
 
An update on my experiment.
Just as a preface, my H1 has a curb weight of about 9000lbs, and my trailer weights about 2000lbs. Brand new P400 (well, about 12k on it now) running about 15psi of boost with the HO injectors, new style waterpump with BRF, HS rockers and a tune. Every other relevant component is OEM... 5.91 drive ratio, 37" tires, yadda yadda....

I've decided to go ahead and remove the EV clutch from my rig as soon as I can source a new OEM clutch. This past weekend I decided to "torture test" the system after it had performed adequately but not as I had wanted over the past month. I tossed on my 2000lbs trailer and then ... drove over to the White Mountains National Park in New Hampshire. Now these aren't the Rockies by any means, but there are a couple stretches of multi-mile 5-7% grades. The way to my destination, I used the override and the ECT temp reported by the ECM got to 208 but could only really do 45mph ... I had a bit more power available to me but I dared not give it more.

On the way back however, I came across an issue where, after a long downhill stretch of road, the fan clutch would stay engaged (due to lack of engine RPM, not enough of a grade to downshift) but, once I got to the bottom of the hill and had to give it the go pedal, it would finally disengage - only for my temps to go from 177 to 210 within 30 seconds. And the clutch wouldn't re-engage. Due to this delayed engagement my highest ECT was 222 and at that point I pulled over and let it cool off. In my opinion, the controllers - that are made for electric fans, not clutches, do not have the proper PWM frequency to control the clutch solenoids like they would a fan - and the clutch is simply too slow to respond to how rapidly my ECT's can climb.

The rate of temp increase in my coolant - which only happened after I converted to the EV clutch makes me think that the OEM thermo clutch has a baseline % engagement above that of the EV clutch - in other words, the thermo clutch is engaged more than the EV clutch is at lower temps.

This of course could be duplicated in the EV clutch - however you'd need to have a custom controller developed for it. Ideally, getting the PWM frequencies from the ECM's that use these EV clutches stock would give a much better idea of how to program a controller.

It's been recommended that I change the location of my sender. I might try that. Since the sender now is between the t-stats and the radiator, it doesn't get a constant flow of coolant over it - but that shouldn't matter for the delayed engagement as my t-stats are 180's and should be well and fully opened by the time 200'F comes around.

I'll maybe use the controller to control an electric helper fan. We'll see.
 
@CursedH1
Your assessment of less airflow before engagement makes sense. Getting the better disengagement is one of the poser saving advantages of the electric units.
And the fact that the “system” works in pickups but is failing in the hummer: pickups have better airflow over the radiator due to vertical positioning as opposed to being laid back at the crazy angle. So “no” airflow in a pickup is still self generated airflow from driving forward but we get almost none of that in a hummer.

As discussed before, there are some people who get acceptable results running an electric fan in conjunction with the mechanical on hummers. Most of them admit to never exceeding 65mph, and most never exceeding 55mph. Up to you how long you want to play science experiment boy, and can’t believe I am saying it but I wonder if the electric mustang fan that @Hummer H1 (Eric) is suggesting elsewhere would eliminate the problem. If the mustang fan came on at say 200° and went off at 190°, would that help the delay action of the other fan in place?

My only other thing I question is finding a thermal switch to just a relay for the thermal viscous. That is on/off without the wide thermal control band of these controllers.

I fully understand the advantages why you wanted them, but if you can use the mustang fan to help the a/c- then have the other only function for the ect- it might work.

It sounds like you might end up going with the mustang one in the near future anyways because running the oem will get you back to square 2 (sq 1 would be before the brf).

Yes, the ect sensor in the head is a worth while test before chucking it all imo.

Sidetrack:
The pickup guys never experienced the unhappiness of removing the center console to get to the back of the engine hummer owners face. Removing and installing basically eats most of a day of annoying work that is semi difficult and having to be careful to not damage the interior. By far the thing I hated the most on hummer vs pickup wrenching days. They are impossible to replace if damaged too. Mine got destroyed by a thief years ago and I was so upset obviously ($5,000 when they were available) but once gone for 6 months I didn’t miss the idea if removing/installing it. But it is so ugly now that I have to build something new. Just now it will be something easier to deal with is the plan.

There is one other thing I would play with before giving up on the experiment but it isn’t actually the fan. It is a fatal flaw that requires the BRF to make the coolant system even work “ok” not “good”. The dual thermostats without a bypass blocker. I have a crossover I am gonna try when my engine goes together.
If the one I have won’t fit from the pickup to my set up- I am 100% going to buy the inline remote bypass style thermostat holders I have shown before. Complete stopping of the coolant flow between engine and radiator is done in 98% of all rigs since the 1970s for a good reason and GM just rolled the dice on this dual stat system and I’ve seen nothing but issues the whole time.
I’m not saying it will or won’t fix your issue but if in your shoes- I would try it.

EVERYONE I can ever remember that has ever experimented with block off versus non-block off, ends up going with the block off. I don’t wanna dive way into that on this thread- huge derailment. Two paragraphs isn’t bad but lets jump to different thread for that subject if interested- and I will dig up the remote ones I am referring to and just post link here for reference.

On the specific design pwm for this electro viscous clutch- yes that would be ideal for everyone. It would have marketability across the aftermarket automotive industry not just us 6.5 nut jobs.
 
even though I run a pickup, I'm not too thrilled about the delay engagement on the fan clutch. I would like to see it release sooner too, but have learned to deal with it. I have noticed that when I'm on the freeway, I cannot hear the fan roar like I used to until I slow down a bit or take my foot out of the go pedal. I think I have only had this setup installed maybe a year (CRS syndrome is rearing it's head). I really wish there was a bolt on or spin-on setup that would turn the fan clutch into a full on electric or air driven clutch similar to ether a ac clutch or smaller version of the big rig fan clutch.

I think this would take the win over all of the mods out there.
 
when mine engages while up to speed rpm up over 2k you never hear the fan. but at the first instance I take my foot off the pedal or slow down any, you hear the roar, the roar will continue back up the speed sounding like a tornado under the hood up over 2k rpm until the controller turns off the fan clutch. when I first installed it and up until a couple months ago I could be going on the freeway, when the controller turned on, there would be a short delay and then ROAR under the hood similar to how you hear the big rigs at high idle. it doesn't do this any longer.
 
I need to do that. also want to see if I can read the rpm signal with a multi-meter at least possibly see if it's fully locking up when on. I know I won't see actual RPM but if it's a simple pulse generator I should be able to tell when it's fully off and when it's at full lockup.
 
dbrannon79 said:
I need to do that. also want to see if I can read the rpm signal with a multi-meter at least possibly see if it's fully locking up when on. I know I won't see actual RPM but if it's a simple pulse generator I should be able to tell when it's fully off and when it's at full lockup.
Click to expand...
The hall effect sensor in the clutch has a 5V reference signal. I've picked up a couple of cheap hall sensor displays on amazon to see if they could work for our application but I haven't had the chance to really dive into making them work. Finding one that works off of 12V DC but has a 5V reference is tough because they all use the power supply as the reference voltage. I was going to try to use a DC power supply that I can turn down to 5V but then I couldn't actually move the truck (It's plugged into the wall).

The hall effect sensor is something that would definitely play into a custom controller. In an OEM setup, I'm guessing that this sensor reading is fed back to the ECM which uses things like ECT, ambient air temp, Intake temp, transmission temp and MAP/Boost reading to calculate the rpm of the clutch vs the rpm of the engine, and adjusts the PWM frequency/duration accordingly. Such a system would be pretty tough to replicate but not impossible.
 
Just found this thread over at another forum from last year. Seems a guy did a similar setup on his GMT400 conversion van. He said he uses a "P59" to control the PWM fan. Does anyone know what he means by that?

Electronic Fan Clutch Information

I am reserving this thread for a writeup on the PWM controlled Trailblazer electronic fan clutch swap. I will be adding information on how to wire it and control it in the near future. The P59 controls a solid state relay that sends a PWM signal to the clutch. The clutch has a RPM feedback...
www.gmt400.com www.gmt400.com
 
Just stumbled across this great thread from 2019 discussing the very same issue that I've been hypothesizing about. Indeed it seems that the PWM frequencies from the PWM fan controllers are too high for an EV clutch. Looks like a fellow 6.5 guy was running the EV clutch back in 2019. Any one of you guys? :p

Electric Viscous (Mercedes) Fan Clutch Control

This discussion bounced over here from Facebook because - well, Facebook. A few folks that have installed the Applied/Tom Pryor Mercedes EV fan clutch have been unhappy with the on-off controller that is provided with the product. It seems that it is continuously cycling on and off every few...
www.gmcmotorhome.org www.gmcmotorhome.org

1722558195653.png
 
That’s an interesting looking controller. Looks extremely simple and even serviceable too! I would remove the relay contacts and add some heavy wires to have the relay by remote and easier to work with.
 
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