heat sink

[murd450]

i dont have the money for the heat sink kit so i made my own from an air cooled lawn mower head !not shure how it is going to work we will see if this pmd last longer than 4 months (the old one quit yesterday morning at 4 mo old) :mad:

[awake1630]

Question when you PMD quit did you lose any dash lights. I believe my PMD quit on me last night. When it stalls i lose the Service Throttle Soon light and the Wait to Start light. I have to wait appx. 10 mins for this lights to come back on and the truck will start again and then die very fast.

Thanks

[jifaire]

i dont have the money for the heat sink kit so i made my own from an air cooled lawn mower head !not shure how it is going to work we will see if this pmd last longer than 4 months (the old one quit yesterday morning at 4 mo old) :mad:

I'm assuming you are putting a used or old PMD on your homemade heat sink?

That might affect the longevity, too.

[grancito]

Question when you PMD quit did you lose any dash lights. I believe my PMD quit on me last night. When it stalls i lose the Service Throttle Soon light and the Wait to Start light. I have to wait appx. 10 mins for this lights to come back on and the truck will start again and then die very fast.

Thanks

souds like no power to the switch or bad switch, a bad PMD won't do that.

[murd450]

i am using used pmd's !no money for new ones:mad: !but that is why i am puting my own heat synk on becase i am out of them forthe time being ! and for the guy whith the stalling problem , it does sound like a power problem to the puter check the ignition switch , bat wiers ,and the wires going to the fuse boxes ,and check the fuses ,sounds like the comp is loosing power some where ,or ground be shure to check all youre grounds if that dosent work check the wieres at the comp , but dont probe the wiere it self find a plug on the circet and back probe the plug if you probe the wieres you not only change the resistance of that wire (buy brakeing strands in it you allso make a place for water to get in and rust the harnes)but it just isent good :cool:

[jifaire]

i am using used pmd's !no money for new ones:mad:

There are 2 problems with that statement...

1) By utilizing used PMDs, you will never know if your somewhat unorthodox heatsink works. Used PMDs have already been baked - they've been taken off a vehicle for a reason - and so their lifespan, on even the BEST heatsink, is arbitrary.

2) Following the logic above, sooner or later you spend more in used PMDs than you would just buying a new one. Add to that the safety effect (when your PMD dies, so does your steering and brakes), it makes you a hazard to others if it dies when merging onto the freeway or in traffic, or it could leave you stranded somewhere.

Used PMDs are like used condoms... I'm not all that sure I'd want to bet the farm on them.

[torque454]

Ive been screwing around with some older computers latly (pentium 3's) and now i have a few extra P3's with big heatsinks on them. Think those would work for a PMD ?? Theyd have to be modified... but that'd sure beat $100+ for a heatsink. Especially when i only paid $5 or each of the processors WITH the heatsinks on them. A couple of them even have fans on them. :) Dont know what volts they take tho....

[Chevylover]

Computer fans runs on 12V !

:-))))


Cu,
Sven

[DieselFreak]

Yes, computer heat sinks w/ fans might actually be a very good idea to effectively cool off the PMD. Used computer fans are more or less for free (I throw some away all the time), and a NEW heat sink w/ fan shouldn't cost you very much.
Nice idea, Torque :cool:

[jifaire]

Wrong size. Too small, not enough mass, fin depth is adequate but air gap is too small. They'll need fans to even function to their design capacity, and computer fans in a dirty or wet environment are really iffy.

I sure as heck wouldn't want to trust my expensive PMD to a heatsink that, sans fan, actually attracts more heat than it sheds!

[bigde53]

I put a old computer fan on a home made heat sink about a year ago still works fine. It was 12 volts so I wired it to the fuse box on the inner fender.

[jifaire]

I put a old computer fan on a home made heat sink about a year ago still works fine. It was 12 volts so I wired it to the fuse box on the inner fender.

You're talking about a case ventilation fan, not a CPU fan, right?

If you have the PMD under the hood, having a fan on it does no good. All a fan can do is circulate air... under the hood, the ambient air temp can exceed the temperature that the PMD can create on its own.

Tell me, what good will it do to have the fan pushing hotter air onto a heat sink? The heat sink will be absorbing MORE heat and heating up the PMD more.

A fan by itself will not create cool.

[grancito]

I agree, put the PMD outside the engine compartment!!!

[torque454]

I'm gonna try the Pentium 3 heatsink on the pmd, but outside of the engine compartment and with the fan on it still. Its not too much bigger than the pmd itself, but out in front of the radiator it should be plenty big. Bear in mind the fan pulls cool air in while at idle and the force of the vehicle in motion forces air across the heatsink also. The engine produces more heat than the PMD could ever dream of, and in the winter you really dont even need an engine fan while driving, the cold air forced thru the radiator is enough. You may not even need one in the summer, i cant imagine a small-ish fan pulling more air thru the radiator than mother nature forces in under motion. With all this said, a P3 heatsink should be sufficent mounted behind the grill.

[DieselFreak]

Wrong size. Too small, not enough mass, fin depth is adequate but air gap is too small. They'll need fans to even function to their design capacity, and computer fans in a dirty or wet environment are really iffy.

I sure as heck wouldn't want to trust my expensive PMD to a heatsink that, sans fan, actually attracts more heat than it sheds!

Wrong Size ? You can get CPU heat sinks in any size and form. You only need lots of mass when not having a fan. Having a fan IS their design.
I don't know the exact temperature generated by the PMD, but I expect it to be similar to a CPU. I have a CPU that runs with 140 F daily, and with peaks somewhat higher. (Heat sink and fan is OEM)

But you're absolute right about the environment.

With a fair CPU heat sink and a low noise fan (80-100mm), then why not even try to put the PMD inside the cab ? Perhaps even a large heat sink and then no fan?

In my wife's car I have installed an in-car-computer sitting behind the dash (no air flow). Low profile heat sink w/ low noise fan, and it never had problems running too hot.

Just my $0.02 :cool:

[bigde53]

You're talking about a case ventilation fan, not a CPU fan, right?

If you have the PMD under the hood, having a fan on it does no good. All a fan can do is circulate air... under the hood, the ambient air temp can exceed the temperature that the PMD can create on its own.

Tell me, what good will it do to have the fan pushing hotter air onto a heat sink? The heat sink will be absorbing MORE heat and heating up the PMD more.

A fan by itself will not create cool.

It was the bigger fan off of the power supply and it made a difference in how hot the heat sink got just by the feel of it. The fan is pulling heat off the heat sink how could it not help?

[jifaire]

It was the bigger fan off of the power supply and it made a difference in how hot the heat sink got just by the feel of it. The fan is pulling heat off the heat sink how could it not help?

Fans can't "pull heat off" anything... they can only circulate air. If the fan is "pulling hot air off the heat sink", other air is rushing in to replace what the fan is removing.

The question then is, 'what temperature is the replacement air at?'

If it's coming from underhood, it's probably as hot (or hotter) than the heat sink was to start with.

If the fan was pushing air onto the heat sink to displace the air that had absorbed heat from the device, then again, the question is 'what temperature differntial exists between the new air and the old air?'

This is basic thermodynamics. Fans don't create cool. They only move air.

If the air is all the same temp, then fans don't cool anything. The only way a fan can cool something is by bringing in cool air to replace the air that gets heated by the device.

[DieselFreak]

Yes they circulate air. But the air surrounding the heat sink will be cooler (at least not as hot) than the surface of the heat sink, thus having a cooling effect.

LOL ever heard of the "windchill factor" *ggg* (just kidding).

[bigde53]

When it's 100* outside I put a fan on me and it feels good and cools me down even though its blowing hot air back at me. Without the fan the heatsink was almost to hot to touch but with the fan it is noticably cooler so I feel it will help out you dont have to.
All I was getting at is a computer fan will live under hood as mine has been there for over a year without a hitch.

[murd450]

There isent any thing wrong whith a free used pmd,if it is free it is for me:D :D

[JD_countryboy]

a burned up pmd is still used but not ok. You would have wasted your time swappin a bad pmd with another junk one. I work cheap, but even my time is worth somethin.

[murd450]

they are good used i took them off the engines my sellf ,and it akes no time at all to change them they just lay on the valve caover at the moment , and to the guy who said the computer heat sink isent good enuf ,any thing is beter than nothing at all and the fan it sellf dose nothing at all you are right it is the air moving acrossed it ,and i dont know exactly what the tmp is on a pmd but i know you cant touch it so if it only pulls away 100f of heat that could make it last just that much more ,and a week and 4 days is still beter than a week:D