Moving my PMD

[monte0172]

I have a 99 2door tahoe and Ive been having the intermittent dying and slow acceleration problems that eveyone complains about so i decided to go ahead and move my PMD so I bought my own heatsink and modified it how I want it and ill let yall decide what you think of my decision and where I located it. Oh it a used pmd that i got off ebay also. What can I say not alot of money right now so close to x-mas. Heres a link to my website with the pics posted. http://www.bigtjohnsons.com/pmd_relocation.htm

Let me know what you think.
Terry J.

[Nomad]

I have mine installed at the same place where you put it, It still get Hot
So I moved it underneath the Bumper by the license plate, and i'm telling you it gets hot to 21 C compared to inside the engine bay of 37 C upward

[Husker 6.5]

I have a 99 2door tahoe and Ive been having the intermittent dying and slow acceleration problems that eveyone complains about so i decided to go ahead and move my PMD so I bought my own heatsink and modified it how I want it and ill let yall decide what you think of my decision and where I located it. Oh it a used pmd that i got off ebay also. What can I say not alot of money right now so close to x-mas. Heres a link to my website with the pics posted. http://www.bigtjohnsons.com/pmd_relocation.htm

Let me know what you think.
Terry J.

Looked at your photos of your homemade PMD heatsink. More than adequate for disipating the heat off the PMD (I'm using the heastsink off a bad 277V frequency inverter to control a 5HP electric motor that I cut in half, and still have over 220 sq.in. of radiating surface on a 1/4 in. base that is 5" x 6 1/2" with the fins 5" long and 1" tall, 22 in all), HOWEVER: For maximum cooling efficiency you MUST have each transistor on its own set of fins, not sharing them as it appears in your photos. The long axis of the PMD should be mounted perpendicular to the axis of the fins, so that each transistor is disipating its heat into its own set of fins. Mounting the PMD so the long axis is parallel to the fins puts the transistors side by side under the same 3-4 fins in a very small footprint, which creates a hot-spot similar to being IP mounted. Much harder to disipate the heat. I know it might be a small pain to do it, but rotating your PMD 90* and redrilling/tapping the holes so that the transistors have their own unique set of fins WILL both drop the operating temp of the PMD, and increase its longevity. This is assuming that your E-bay used PMD is not on its last legs, as there have been many cases of latest version PMDs that have failed once and gone into "limp" mode being sold as "good" used because they worked fine on next restart(s). The only way you can be positive about a PMD is to buy it used from someone you know and/or trust (but if it is "good" why did they replace it/have an extra?) or buy a new one from a reputable source.

Hope this helps.

Husker 6.5

[deerefanatic]

It's still gonna get too hot in there......

Move it to the bumper or grill (like I did)...... You'll be glad for it........

[monte0172]

Husker I see what your saying about the fins and rotating it 90 degrees. I will do that. I was debating on that anyway. As far as the used one well just have to see. The guy has sold alot of them and not had a bad review so Ill just have to see. If not mines working ok it just has intermittent problems. I was also going to move the fender heat shielding so that air get through the fender to it as well. Kinda like the other side with the airbox. I was going to move it to the bumper but I just haven seen one that i think looks good. I like the stock look and a huge 12" heatsink hanging in my bumper or grill just dont look good to me. I know Functionality before looking good but being a mechanic for 15 years I prefer both.

[monte0172]

Has anyone ever came up with a plan for cooling fans on the pmd cooler? I have a plan to use two fans and a thermal switch to turn them on and off I just wanted to check to make sure i wasnt reinventing the wheel.

[deerefanatic]

You're re-inventing the wheel..... Passive cooling is always best because there's nothing to fail..... Mount out front and be happy.

Plus, even with thermostatic fans, once you shut the truck down, the fans are just circulationg 180*F air around....... Which isn't helping your PMD at all.....

[ibsurfing]

Nice heat sink, where did you find it?:)

[deerefanatic]

Ebay....

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[monte0172]

Yeah thats it. I modified it to work for what i want. I found it on another post here not sure which one though. I just got my extension harness today and will be turning the pmd tonight or tomorrow and hooking it up.

[deerefanatic]

I see the mods are out squashing the competition! :D

[Garth J]

yep and no direct links please

[monte0172]

Ok everyone I have an issue. I redid my heatsink and then plugged in my extension harness from the pump to the new PMD well used. and now it run for about 30 sec and died. started again and same thing. I think it might be bad but I wanted to ask one question first. What is everone doing for a ground when they use an extension harness? I left mine grounded to the original location and im thinking i need to ground the new heatsink to a good ground location. What do yall think or know? Pictures would be great as well.

[grancito]

Even with the ground wire that was on the pump, is connected to the heat sync, the engine will not run if the heatsync/PMD is not grounded.

[monte0172]

Thats what i thought. Its bolted to a bracket that bolts directly to the body so it should have sufficient ground. Im going to run another ground wire anyway. But what it does it it runs for about 30 sec to a min and then shuts off and wont start again. At least before it would run for awhile and intermittently shut off and wouldnt start. But thats what i get for buying a used PMD. But the guy is sending me another so not to big of deal. I also thought about the Fuel shutoff solenoid and considered replacing it but Have to order it as well considering no one carries these things locally. Think it might be a good idea anyway?

[grancito]

Try the replacement PMD first.

[monte0172]

Well i finally got my replacement in and got another heatsink and made it look a little more professional than the first and mounted everything up including a ground for the heatsink to the block and everything runs like a champ. Thanks for all the help and if i ever get a chance to take more pictures ill post em up. Thanks again.