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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, MPG computer for Brougham in Past Cadillac Vehicle Discussion; Originally Posted by Fleetwood472 If I come across another 4100 at the yard I am going to try to trace ...
  1. #46
    cadillac kevin's Avatar
    cadillac kevin is offline Cadillac Owners Master
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    Quote Originally Posted by Fleetwood472 View Post
    If I come across another 4100 at the yard I am going to try to trace the wires back to see where they go. Did you grab a wiring harness for yours? How many wires were coming off of the back of it?
    IIRC, I traced the wires back on a V864 and they went to the computer

  2. #47
    Fleetwood472 is offline Cadillac Owners Fanatic
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    Re: MPG computer for Brougham

    Do any wires goe to the ALDL port under the dash?

  3. #48
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    Re: MPG computer for Brougham

    A wire is going to the ECC control head which is also HT-specific.
    I think, it is a huge system and is not possible to install into another car (except you install the HT4100 and everything else too ). It even needs information from the tank to calculate the "miles to empty" value.

    Here's a pic of it. The wire on the left side of the ECC control head goes to the fuel data display. It doesn't work without the ECC control head!



    Regards
    Felix

  4. #49
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    Re: MPG computer for Brougham

    Quote Originally Posted by Fleetwood472 View Post
    If I come across another 4100 at the yard I am going to try to trace the wires back to see where they go. Did you grab a wiring harness for yours? How many wires were coming off of the back of it?
    I pulled out and could get about 6 inches and cut it there. It is out in the trunk now, but as I recall it had about 70 wires coming out of it! Well, maybe 10 or 12 but it seemed like 70....

  5. #50
    Bro-Ham's Avatar
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    Our forum friend Sven converted one of these MPG gauges into a temperature gauge if I remember correctly. The thread was interesting, but it involved removing the inside of the MPG 4100 gauge and installing a temp gauge behind the lens.

  6. #51
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    Re: MPG computer for Brougham

    I read that one already while doing my search on the subject here. That was how I came upon this old thread!

    Looked good, but I was hoping to get the function of the fuel data. Had it on my 82 and loved it.

    Before I would do that, I print 28.4 MPG on the lens and backlight it, just to mess with people!

  7. #52
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    So you moved from Madison to Fantasy Island?

  8. #53
    Big_Al1911 is offline Cadillac Owners Member
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    Re: MPG computer for Brougham

    Per the 1985 Brougham FSM, pages 8A-56 and 8A-203:
    The fuel data module has 2 wires that connect back to the ECM to indicate the selection of Instant/Average fuel data and reset. It also has 12 wires that go to the Electronic Climate Control, 11 of which are titled "Control Circuit Lines" and one which is only labeled ".5 Lt Grn" (20ga Lt Green). And one ground wire. So it is pretty close to 70 wires...

    It could be possible that the later models have the capability in the ECU and Climate Control, at least for those that have same style of climate control. The ECU apparently calculates the display values, and sends all data to the climate control via a serial link. I do wonder if it is RS-232 such that it could be tapped? The 11 "Control Circuit Lines" are enough to provide a binary value from 0.0 to 99.9 (observation on my part). I don't see any definition of the exact pinout of the 11 wires in the manual.

    Big Al
    talismandave likes this.

  9. #54
    brougham is offline Cadillac Owners Master
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    Re: MPG computer for Brougham

    I thought they got rid of that display when they went with the 5L engine. It uses a complete different ECM and there's probably too many variables involved with the carberator to figure out how much gas is actually going thru it.

  10. #55
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    Your car still gets 15 mpg regardless of what spending endless hours figuring out how to hook up the MPG sentinel takes.

    A novel gadget in the era the V8-6-4 and HT4100 cars were new, but as quickly passed by when incremental fuel savings were inconsequential. If you want a prius you can have a gauge like that fully functional. In a Cadillac it is a disgrace.

  11. #56
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    Re: MPG computer for Brougham

    If GM hadn't been typical GM and actually put the best motor they made into supposedly the best car they made . . . .

    We would have had a 1986 Fleetwood Brougham powered by a then state of the art "Tune Port Fuel Injected" Chevrolet 350 V8. With about 220hp and 330lb-ft of off idle torque, the big Brougham would've been a rocket ship by 1986 standards. Plus it would have had an MPG computer, something the 1986 Vette had as standard equipment.

  12. #57
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    Quote Originally Posted by Aron9000 View Post
    If GM hadn't been typical GM and actually put the best motor they made into supposedly the best car they made . . . .

    We would have had a 1986 Fleetwood Brougham powered by a then state of the art "Tune Port Fuel Injected" Chevrolet 350 V8. With about 220hp and 330lb-ft of off idle torque, the big Brougham would've been a rocket ship by 1986 standards. Plus it would have had an MPG computer, something the 1986 Vette had as standard equipment.
    You're forgetting the Brougham was not a contemporary luxury car by 1986 and was purchased by white haired buyers for which the old 307 was probably just fine since they likely weren't in a hurry.

  13. #58
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    Re: MPG computer for Brougham

    Quote Originally Posted by Bro-Ham View Post
    You're forgetting the Brougham was not a contemporary luxury car by 1986 and was purchased by white haired buyers for which the old 307 was probably just fine since they likely weren't in a hurry.
    Yeah but I do like to have enough power to pass somebody on an uphill grade. Or not have to put my foot to the floor and lose speed up a hill when the car is full of people and luggage.

  14. #59
    pompste is offline Cadillac Owners Connoisseur
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    Re: MPG computer for Brougham

    Quote Originally Posted by 90Brougham350 View Post
    I've been told that the reason GM didn't give the Brougham and last generation DeVilles was that they were typically sold to an older generation, which had no desire to be pressing buttons and switches on an info center while driving down the road. The 80-89 Towncars had them and they worked great, only problem was, don't try too much while rolling down the highway!

    Brian
    That does make sense.Usually older people have slower reaction times--it happens with age--and they liked things uncluttered and simple.On board displays were relatively new back then and might have been a real distraction to the elderly while driving.

  15. #60
    Bro-Ham's Avatar
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    Quote Originally Posted by pompste View Post

    That does make sense.Usually older people have slower reaction times--it happens with age--and they liked things uncluttered and simple.On board displays were relatively new back then and might have been a real distraction to the elderly while driving.
    I think most mature Cadillac owners then and now could care less about superfluous gadgets. They simply want to get to Florida or Arizona for "season" or to the country club or to the bridge game or the cocktail party at Betty and Dick's house.

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