wiring harness digital vs analog

[markseven]

Hi everyone, I was wondering if anyone has a wiring diagram of the plug that goes in back of the digital instrument cluster. Im in the process of putting the analog cluster in. I know the wiring for the analog, i just need to do some cross reference. plus i found i need to add some wires. any help would be appreciated. my e-mail address is duratech@mris.com

[ekooke]

You really need to get the EVTM for your specific model year, whatever it is. Look on eBay for the best price, or go to Helm at www.helminc.com (http://www.helminc.com)

[2manymarks]

What year Mark are you working with?
My shop manual has a schematic and a diagram of a plug "electronic instrument cluster terminals". I might be able to scan and send it email.

[markseven]

Im working on a 87, any help would be appreciated. i have several parts cars (mark sevens, 2 lsc's and a bill blass.) Ive dissected one LSC and i figured out the wiring on it for the analog, just didn't get to the bill blass yet to figure out the wiring for the digital. i have a feeling i will end up making a harness to help out.

[2manymarks]

You have email.

[pro-five-oh]

Because the digital cluster wires into the trip computer and the A/C unit, its a PITA. (it does that so everything can switch between english and metric and look correct)

I wouldn't recommend the swap unless you do a complete dashboard wiring swap.

[ September 05, 2005: Message edited by: pro-five-oh ]

[markseven]

Well those wires are the ones im stumped on ( trip and ac wires) Ive got everything else working (kinda). Do you think the trip minder wires hook into the fuel gauge? it works but only backwards. Ive used the sending unit out of the analog, along with the wires.pluged them into the exact location they came out of. as for the temp gauge i changed the sending unit, i ran a direct wire from the temp sensor, and the tach i ran a direct from the coil. So....... The tach works ,speedo works , temp gauge works, fuel backwards

[ekooke]

markseven,
There's a problem there, in that the analog gauge setup requires a THREE-wire sender from the fuel tank, and the non-LSC (e.g., BB) has a TWO-wire sender. The analog gauge has a small 4-connector interface module on the back, opposite the analog fuel gauge, and a dedicated wire from the sender runs to the interface module, with another wire from the module running to the TripMinder. The digital gauge receives info directly from the sender and shares the info with the TripMinder circuitry. You really should get the EVTM so you can SEE what I mean.

[markseven]

Has anyone ever done this swap with success? Ive got a 87 cd diagram of the wiring. I feel im so close to cracking this thing i hate to give up. like i said im using the three wire sending unit along with the harness out of a LSC. im parting out the LSC and i took the complete wiring harness out of the car. The wiring schematic helps alot, i guess im just missing something. Maybe i will just sell my mark and buy a LSC. Ive got a "base model" mark seven and ive already done alot of the LSC upgrades to it. :confused:

[ekooke]

markseven,
It sounds as if you have two of the wires from the sender reversed. One wire feeds the actual fuel gauge based on a resistance of:
145 ohms = Full mark
22.5 ohms = Empty mark

where the interface module uses the other wire, based on a resistance of:
10 ohms = Full
155 ohms = Empty

Do you see the problem?

[markseven]

do you have any idea how the interface module works? i know it has 4 prongs on it, one is the signal from the sending unit itself, one is a ground, but i don't know the other two( im sure one is hot) I checked the wires on another LSC and i have the wires in the right spot. do you have anything ( diagram) that shows that module on the back of the cluster

[ekooke]

Here are the wiring hookups to/from the Interface Module (IM) from my 1990 Mark VII Car Shop Manual:
LB/PK wire from the IM is to the ignition switch (ACC), DB/LG from the IM is to the Message Center, O wire from the IM goes to ground, and the other O/LG sender wire from the tank goes to the remaining interface connection. Doesn't your CD show you these things? Get the actual factory Car Shop manual.

[markseven]

Thanks for your help!!