DIS Module ?

T

Tech_Greek

Registered User
On the 94/95 should there be any thermal compound behind the DIS to the bracket its mounted on? Should the bolts be new (do they act like a ground).

*Edit: Just found a post that said someone fixed their problem by Thermal Greasing behind the DIS Module on a 94*
 
Last edited:
Tech_Greek said:
On the 94/95 should there be any thermal compound behind the DIS to the bracket its mounted on? Should the bolts be new (do they act like a ground).

*Edit: Just found a post that said someone fixed their problem by Thermal Greasing behind the DIS Module on a 94*
Click to expand...

The procedure I have doesn't mention anything about adding heat sync compound.
  1. Install ignition control module onto ignition control module bracket and install retaining screws. Tighten screws to 2.7-3.7 Nm (24-33 in lb) .
  2. Install ignition control module and ignition control module bracket onto front fender apron (if removed). Tighten retaining bolt to 4-5.6 Nm (35-50 in lb) .
  3. Connect engine control sensor wiring connector to the ignition control module.
  4. Connect battery ground cable.

On the other hand the procedures for the 90 say this:
  1. Apply a 1/32 inch coat of silicone dielectric compound or equivalent to the mounting surface of the DIS module.
  2. Mount the DIS module to the intake manifold. Torque bolts to specification, refer to SPECIFICATIONS .
  3. Connect electrical connectors to ignition module.

Be careful with the wording. Silicone Dielectric Compound is not to be confulled with Silicone Dielectric Grease. The grease will fry a DIS.
 
Last edited:
There is a mistake on the 90 one, as it should be heat sink compound not dielectric grease. Dieletric grease does not transfer heat well.

Frit
 
I used heat seak compound (Artic Silver F5) on the back of my DIS and it seems to have solved my tach drop problem and my bucking issue...hmmm

This IS on a 94/95...I also cleaned up the bolts with degreaser and the bracket to make sure that the four points on the back of the DIS (which I'm assuming it uses to touch the bracket for a ground).
 
The last DIS I put one was not that flat on the backside, so I draw filled it untill it was flat and smooth. I also emry clothed the mounting surface.
 
Ok, so it seems like we're all drawing to the same conclusion (I got the idea from MN12 Performance).

The ground idea is really crappy, they use a tab (and one bolt) to hold the bracket up there (I'm going to take the splash guard off and bend this tab so its more firm on the back side).

They use four points on the back of the DIS Module to actually ground it out on the metal bracket, so if the points are corroded OR the bracket is corroded you get a junk connection.

I wonder how much money people have wasted all for an issue as simple as those four points or the bracket being corroded.
 
Last edited:
Computer heat paste use is a myth. Please don't buy into this type of shade tree mech. repair.

Dielectric is the proper compound. Ford never recommended Arctic Silver computer heat transfer paste. Doesn't make sense to think that way guys. The DIS has enough to tolerate already. In a computer, the processor is supposed to shed heat into the heat sink, which is not a heat source. That isn't what is going on with a pedestal mounted DIS (later years it is on the fender)....why encourage heat from the engine into the unit? Heat rises....

The pedestal runs at engine avg. temp in that location - 175 deg. is what my car shows at that point. The DIS runs at the same temp. as it heat soaks. Yet it runs at 135 if lifted off the pad. You can set the DIS on small thin flat washers and try for yourself.

Use dielectric like everyone else and be happy.

Ken
 
Last edited:
I agree and disagree...

Thermal Compound is used to draw heat AWAY from the source...in other words the heat from the actual DIS unit being in the hot engine bay air will be spread to the bracket which will be spread to the wall...not the other way around.

Its quite possible that the metal shavings in the thermal compound I used are conducting the ground a whole lot better as well...

What should I say when I walk into Advanced Auto - that I want Dielectric Grease, Compound, etc...what?
 
Last edited:
Tech_Greek said:
I agree and disagree...

Thermal Compound is used to draw heat AWAY from the source...in other words the heat from the actual DIS unit being in the hot engine bay air will be spread to the bracket which will be spread to the wall...not the other way around.

Its quite possible that the metal shavings in the thermal compound I used are conducting the ground a whole lot better as well...

What should I say when I walk into Advanced Auto - that I want Dielectric Grease, Compound, etc...what?
Click to expand...

Remember that the earlier SCs mount the DIS on the pedestal - these require dielectric grease.

For the later models, with the redesigned DIS mounted on the fender, I don't see any recommendation for anything in terms of a coating between the module and the bracket or the bracket and the fender - use butter if you like...

As far as asking in an auto parts store - if you have a pedestal mounted DIS, you want dielectric. I not aware of any auto parts stores that sell Arctic Silver...reason :)

Thermal compound as used in computers has no ability to draw, push or otherwise encourage heat transfer other than to promote a consistent mating of two surfaces by removing air pockets. Too much will impede heat transfer and too little won't do anything. It takes a specified quantity to do the job.

On the cars with the pedestal mounted design, with a fully warmed engine, the pedestal is always hotter than the DIS alone.

Ford got into this situation with the TFI's back in the 80's, they used to mount directly onto the distributor. This meant the TFI's would heat soak and die...some owners went thru half a dozen. When a class action suit in Calif. brought attention to the issue (I got $25 each back for two I went thru), Ford redesigned the units and tried to find a location that wouldn't increase the cost of the wiring and maybe not kill the units so often. This was seen in the pedestal mounted example on early SCs.

The later model SCs with the redesigned DIS modules, that include cooling fins and were relocated on the fender, is another example that they were still struggling with failures related to excess heat. If that heat was strictly related to the DIS itself, they would never have invested in longer wires and a fender mounted design where it is no longer in contact with the engine.

Ken
 
Last edited:
Well,

Maybe it was just because I cleaned up all four contact points on the back (which I'm assuming it uses for a ground) and the bracket.

I work on computers, I'm an IT Admin - I know what Thermal Compound does, and it has brought down the tempature of my DIS just by touching it with my hand after WOT it's not burning hot anymore, but yet without it I would burn my hand by part throttling it not even hitting boost down the road before the paste.

I'll leave it on there, it's not hurting anything at this point and if it fries so be it, then I can prove that its wrong to use it and use the other one I have on the way without the paste. :cool:
 
KMT said:
Remember that the earlier SCs mount the DIS on the pedestal - these require dielectric grease.

For the later models, with the redesigned DIS mounted on the fender, I don't see any recommendation for anything in terms of a coating between the module and the bracket or the bracket and the fender - use butter if you like...

As far as asking in an auto parts store - if you have a pedestal mounted DIS, you want dielectric. I not aware of any auto parts stores that sell Arctic Silver...reason :)

Thermal compound as used in computers has no ability to draw, push or otherwise encourage heat transfer other than to promote a consistent mating of two surfaces by removing air pockets. Too much will impede heat transfer and too little won't do anything. It takes a specified quantity to do the job.

On the cars with the pedestal mounted design, with a fully warmed engine, the pedestal is always hotter than the DIS alone.

Ford got into this situation with the TFI's back in the 80's, they used to mount directly onto the distributor. This meant the TFI's would heat soak and die...some owners went thru half a dozen. When a class action suit in Calif. brought attention to the issue (I got $25 each back for two I went thru), Ford redesigned the units and tried to find a location that wouldn't increase the cost of the wiring and maybe not kill the units so often. This was seen in the pedestal mounted example on early SCs.

The later model SCs with the redesigned DIS modules, that include cooling fins and were relocated on the fender, is another example that they were still struggling with failures related to excess heat. If that heat was strictly related to the DIS itself, they would never have invested in longer wires and a fender mounted design where it is no longer in contact with the engine.

Ken
Click to expand...

If dielectric grease was so good as you are proclaiming, then it would in fact be used in computers for heat sink paste since it is so good at not conducting current. However, there is countless number of occurences here and at other websites where people have mistakenly used dieletric grease and suffered alot of problems with the DIS module. Once they used the proper heat sink compound they no longer had issues...

I have also run the heat sink compund on my car and have never had a DIS problem, and the last time I pulled the DIS module off, the compound was still there and had not melted away as you are proclaiming it would. In fact the heat sink compound I use is not only rated for auto use, it is also rated for computer use as well.

If you where right, then I should be having alot of problems with the way my car runs.

Frit
 
Well....I thought we went through this heat sink issue once already. I certainly provided info that the commonly used Artic Silver had sufficent temperature range to be used in this application. In another thread there is NO DOUBT that Ford specified a heat sink compound be used between the DIS Module and Accessory Bracket in the 89-90 Shop Manuals. Why that changed in 91 I don't know but I do know that in 91 the part number for the DIS Module changed too. I am trying to get info on what the change was and why but when Standard took over the DIS Module production I have been assured that a later model DIS Module and early model would both work. (Not counting the 94-95...different system).

Heat ALWAYS flows from hot to cold...just basic thermodynamics. If the DIS Module is hotter than the bracket heat will flow from the module to the bracket. Heat Sink Compound increases the rate of heat flow since it provides more physical contact between the module and the bracket thus increasing the effective surface area. The rate of heat transfer is determined in part by the temperature difference between the parts and the effective surface area. That is the reason both surfaces should be as clean as possible before you install the module....that too increases the effective contact area. The heat sink compound fills in the small peaks and valleys of the machined surfaces. I can't see how using dielectric grease here would do anything but lower the rate of heat transfer since it is both an electrical and heat insulator. I would like to see some data that proves the accessory bracket is warmer than the DIS Module given all the heat in the bracket is from radiant heat in the engine bay (except that originating in the DIS Module or the amount coming from the block itself) as opposed to being "generated" in the DIS Module since that is where the high current draw semiconductor components are located. At each primary coil fire, the DIS Module supplies up to 5.5 amps of current to the coil to be used to fire the plugs. This is occurring for 3 coil packs pretty much continuously so you can pretty much say there is up to 16.5 amps potentially flowing through the module total.

Now you can choose to do what you want with your car. I have a 92 and still used heat sink compound when I replaced the DIS Module. Don't have a 94-95 so I don't have as much experience dealing with their issues but based on what my source of technical information says (Lou Willimas Ex-Ford Drivetrain Development Engineer) you should be using heat sink compund on ALL DIS Modules.
 
The pedestal runs at engine avg. temp in that location - 175 deg. is what my car shows at that point. The DIS runs at the same temp. as it heat soaks. Yet it runs at 135 if lifted off the pad. You can set the DIS on small thin flat washers and try for yourself.
Click to expand...



So, it seems to me that we should all be doing that (elevating the DIS module) and not worry about what kind of goo we use <shrug>

Is there any compelling reason not to? (I'm asking, not arguing). After reading the jillion postings about DIS heat issues I sorta planned on doing so myself.

Cheers
DD
 
Well....one reason is that the DIS Module (at least the early models) are grounded through two of the mounting bolts/screws. Not so sure you want to rely on just the mounting screws for this....but again...do what you choose.
 
Duffy Floyd said:
Well....one reason is that the DIS Module (at least the early models) are grounded through two of the mounting bolts/screws. Not so sure you want to rely on just the mounting screws for this....but again...do what you choose.
Click to expand...


Good reason :)

OTOH, I reckon I can work up a redundant ground easily enough. I've been working on English cars for the last ten years. "Redundant ground" is the name of the game :D

Cheers
DD
 
You must log in or register to reply here.
Back
Top