Man, I'd love to know the model numbers of the parts that you end up getting to work. It's been 104f here for 2 weeks straight and I've been scared on more than one occasion with the needle rising up past half... far past.. That HHR fan just won't cut it for me.. it runs 100% of the time and I can't use A/C.

I went up a 10% grade 1000ft hill by my house with 800lbs of garden stuff and with the A/C on I almost didn't save it from overheating. Turned the A/C off, and threw the heater on full blast ... talk about heat lol. I felt like a boiled goose.

 

Yup, same problem here. I even had the HHR fan on plus a 16" fan pushing and no luck. I have a new rad to install but I need to do a bunch of mods to make it work and have been busy. I am a refrigeration and HVAC guy and with it getting up to 41*C (41x1.8+32) 105.8* for you south of the border, i haven't had time to do anything. It's melting my dang IGLOO up here right now.

Pic of the new double core rad
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Side view
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Imagine what it will be like with that hemi in there. I am anticipating this radiator will work for the hemi swap. I'll do a full write up with p#'s when I get it in. I would like to see this Mark 8 fan work and some complete install picks as well.

 

The Mark VIII fan is good, but like it's cousin, the Taurus fan, it's hungry for amps. In one of my posts on this subject, I included some typical Taurus fan specs on startup current draw - you Mark VIII won't be much different. Without knowing what your controller consists of (most of them are good for about 30 - 40 amps on startup, but over 30 amps continuous will kill the controller eventually), I can't give you any reasonable suggestions.

If you're looking for an automatic controller that will vary the speed of the fan as needed by the temperature, I found only 1 controller that would handle the Ford fans and that's made by Painless - it's close to $300. Building a 2 speed relay controller for these fans that would include 2 thermal switches (1 switch per speed step) is close to the same price if you buy quality components and you don't have nearly the same versatility as you would with the automatic controller (Pulse Width Modulated generally).

You say that the fan will run for a short time before the fuse pops. This suggests to me that you have an automatic controller that's not rated for the ford fan current draw. These controllers normally give the fan a "soft start", which would mean a bunch of small DC pulses to get the fan rolling (this doesn't eat up too many amps), and then at some point the controller increases the PWM duty cycle to accommodate the cooling need & this would be when the fan motor current draw would exceed the fuse rating. If this is the case and you change the controller manufacturer's recommended fusing to something like a slow-blow, circuit breaker, etc., to try to overcome this, you end up putting the load onto the controller that isn't designed to handle it - this can destroy your controller, harness, etc.

 

....or you could get one of these. http://www.dccontrol.com/relay_controllers.htm

 

I'm going to order one of those controllers and just use that, I wish I had seen this post before I ordered a bunch of relays and other stuff to formulate a solution. Once I have a final result I will thoroughly take pictures of the install and give part numbers as best I can.

 

That controller is very hard to get, the manufacturer is very picky about who he responds to and even if you pay him for one, you may be waiting for a long time to get it - there are lots of posts on various sites (including his favorite sites) to this effect. That's why I narrowed the selection down to the Painless unit or a DIY version if you can program a micro controller or if you're satisfied with a relay system. If you understand basic electronics, you can make a solid state unit that will do everything the relay system would but is expandable to add various things like "soft start", PWM that would give various selected speeds based on some sort of temperature scheme where you could switch the output duty cycle on selected signal values (you could hard wire the switching scheme with a few analog or digital comparators). Feeding the low amp pulse train to a power hungry fan motor is fairly easy by funneling that pulse train through a high power MOSFET.

 

Im sooo confuzed on what you guys are all talking about.. once someone firgures out a nice setup will they make a DIY with photos and a supply list.. lol all im looking for is a good not to expensive efan setup with 2 speeds..

 

Here's a schematic that I put together to show a manually controlled, relay based 2 speed fan controller with air conditioner input - I'll add a version of this, as I have time, to show the addition of thermal switches for Hi/Lo/Off selection based on coolant temperature vs manual switching and I'll also add a basic parts list to help out those that don't have much of a local selection of parts.

 

For Pulse Width Modulated (PWM) controllers that have the "smarts" to run an automobile cooling fan and are robust enough to live in an engine bay AND run a Ford fan, my only recommendation is the Painless unit. Here's a link to the product. They also have one that will work with 2 hi-amp fans.

To build one that has all the "bells & whistles" would require a reasonable amount of time & effort, a simple manually controlled version of a PWM unit that could vary the speed of a Ford fan isn't the issue (you can buy one of these already assembled for about $50 - $75, it has 2 ***** for frequency & duty cycle control and an optional LCD to tell you what you've set), it's adding the overall micro controller along with coding the software to run it that takes much of the time and effort in building and testing. I've played around with this recently as I've had spare time and have created a manual controller for the ford fan, programmed some PIC micro controllers with some basic instructions to make it look automatic, but personally, I wouldn't want to rely on any of my early versions, so I won't be installing them in my truck (I don't have the time to fully develop & test them to my satisfaction). I did a bit of a trial to see if I could modify the SPAL controller to give it a greater amp range, but unfortunately, that didn't work out - that controller essentially shuts down when it doesn't detect a minimum load of about 4 amps & my approach of using a simple MOSFET switch put almost no load on the controller, so it figured that no fan was connected. I looked at adding a dummy load, but decided against this since it wasn't really leading to anything fruitful and was adding to the modification cost considerably.