DIY: FSD/PMD with its own dedicated fan

[red_1995_k2500]

So we all know that heat kills these things when under the hood and continue to be hot after the vehicle stops even when relocated. So this brings to mind the question, has anyone attached a dedicated high-flow computer cooling fan to their PMD? I am thinking of doing this when I relocate mine with a 5-7 minute timer that starts when the vehicle is turned off, maybe even find a way to run a thermo sensor to it. I run a dedicated 10 inch fan on my Jeep with the trans and P/S coolers sandwiched together and works great, so why wouldn't a similar idea work on the PMD heat sink?

[VanBoy]

That is an interesting idea. But from the reading about PMD's, it is not the heat that the PMD generates that kills it. It is being heat soaked from being in the engine compartment- the heat from the engine. The thermal expansion/cooling is what they say takes it's toll on the solder points on the printed circuit board.

If you relocate it to the popular suggested location, bumper mounted, the only heat it would deal with is the ambient air temperature. The train of thought is, if the heat sink large enough, and the PMD is mounted correctly, the heat should transfer to the heat sink when off. I suppose a fan mounted on the fins to draw air over it for XX amount of time would work. There isn't that much room in the bumper. A fan could help, look at small gas engines....air cooled w/ a fan. Diddo w/ the old VW Bug's/Van.

(On a side note, there is a similar issue w/ the Ford 6.0L diesels. They have a unit to control starting/injection/glow plugs and it sounds like something goes out on it too. It is mounted on top of the valve cover, above the exhaust manifold (smh). Dorman has a board that you replace inside it vs replacing the whole thing....)

[Steve83]

Why add weight & complexity when there's already a fan that works? Click this & read the captions:

[racer55]

If you don't put the PMD any where it can get exposed to an external heatsource and it is mounted to an adequate heatsink there is no need for any airflow at all.

Convection/conduction will dissipate the heat generated by the PMD when in operation and keep it at or very near ambient temps at all times-there will be no thermal shock that it gets exposed to and therefore have the best chance at a long life.

[edzzed]

what you could do is order a kit from http://www.frostfighter.com/fixit.htm I have their rear defrost switch and relay which I use to run the heated Ebay mirrors on my truck. It turns on for 11 minutes then shuts off. Rather than running heated mirrors you could run a 12 v fan. Then every time you shut the truck off hit the button and it will keep air flowing for 11 minutes then shut off. Here I wouldn't worry about it since it is rare to see ambient temps above 85f. The way I have my pmd mounted, it gets air flowing past it when the truck is idling and it is below the radiator as heat rises.

[VanBoy]

Originally Posted by edzzed

what you could do is order a kit from http://www.frostfighter.com/fixit.htm I have their rear defrost switch and relay which I use to run the heated Ebay mirrors on my truck. It turns on for 11 minutes then shuts off. Rather than running heated mirrors you could run a 12 v fan. Then every time you shut the truck off hit the button and it will keep air flowing for 11 minutes then shut off. Here I wouldn't worry about it since it is rare to see ambient temps above 85f. The way I have my pmd mounted, it gets air flowing past it when the truck is idling and it is below the radiator as heat rises.

Oh, that's cool! I've been looking for something like that! JC Whitney use to have kits, but not sure if they sell.... plus, I've asked my local parts store if there is a universal defrost switch/timer....for a project....but they just looked at me funny....

[JMJNet]

You are not the first person to have that idea.

Some member here actually have done some research on the topic.

See, inside the hood of a diesel engine is different compare to inside a computer case.
In a computer case, while there is heat, most of the heat comes from CPU and the ambient itself does not generate heat.

Inside a diesel engine hood or any car engine, the engine generates heat while the PMD also generate heat. If you understand Thermodynamics, heat flow from high to low temp. If the PMD generating heat and the engine generating even more heat, the flow of the heat goes from engine to heatsink to PMD. While we need it to be the other way around.

That is why putting PMD in an ambient environment in this case outside the hood where the temperature is hopefully lower than the engine and lower than the PMD, it lets the PMD cools down.

Even if you put a fan, inside the hood, the fan will just attract the heat.
Outside, you don't even need a fan because automatically the temp is lower.
Well, unless you live in Phoenix or Dead Valley. You need to buy Heath's PMD with 7 yrs warranty.

[red_1995_k2500]

Originally Posted by JMJNet

You are not the first person to have that idea.

Some member here actually have done some research on the topic.

See, inside the hood of a diesel engine is different compare to inside a computer case.
In a computer case, while there is heat, most of the heat comes from CPU and the ambient itself does not generate heat.

Inside a diesel engine hood or any car engine, the engine generates heat while the PMD also generate heat. If you understand Thermodynamics, heat flow from high to low temp. If the PMD generating heat and the engine generating even more heat, the flow of the heat goes from engine to heatsink to PMD. While we need it to be the other way around.

That is why putting PMD in an ambient environment in this case outside the hood where the temperature is hopefully lower than the engine and lower than the PMD, it lets the PMD cools down.

Even if you put a fan, inside the hood, the fan will just attract the heat.
Outside, you don't even need a fan because automatically the temp is lower.
Well, unless you live in Phoenix or Dead Valley. You need to buy Heath's PMD with 7 yrs warranty.

I mentioned that the PMD will be relocated in addition to the fan, this will not be under the hood. I may even drill a hole in the firewall to mount the PMD in the cowl area, couple different ideas.

[JMJNet]

As said by all people above, if you put it outside the hood, you won't need the fan anyway. Ambient is enough to shed the heat.

Outside is like bumper or in front of radiator, etc. Not firewall, etc.

Use a rather big heatsink. I used industrial size heatsink with thick base and tall fins.

It is up to you, it is your truck. You can experiment as your heart desire.