Tach cluster into a L trim car

[needragr]

I just pulled the cluster out of my 89L.
It was updated by the PO at some point to a tach unit (oranage).
The reason I pulled it was it had a seriously screwed speedo (bouncy @ low speed & pegged @ hi) and no gas gauge operation (always empty).
What I found was a pair of wires jumperd to screws on the circuit board that routed thru the firewall to the coil. ??
I pulled the R. seat & tested my sender ...good
I cleaned the connector's reassembled then I tested continuity of the yellow wire from the sender to the connector under the dash...good
So Im replacing the cable which I think will solve my bouncy speedo, but how do I proceed with the gas gauge?
Does it also have to be externally wired (two wires from circuit board to coil)?
So what is the wire loom difference between the L & LX?
The wire loom for the body including the tank sending wire(s) are the same, until they connect to the loom section under the dash.
Against conventional wisdom apparently the L & LX DO have a different loom section running behind the dash connecting things like HVAC ctrls, cluster, R window ctrls, AC, pwr mirrors ect.
Perhaps not all, but mine.
The 1st indication that something was amiss was when I went to plug in the pwr mirrors only to find there were no connectors.
Now Im faced with swapping a LX dash loom (which looks to be a MAJOR PITA) or independently wiring all the options not installed on my car.
Has anyone BTDT?

I just want important indicators like my gas gauge & speedo to WORK!

[navdoc101]

No difference I can find.
I have a '93 L & pulgged in power mirrors, & Tach cluster with No problems.
The plugs/wireing for rear wipers is behind the blanks in the Guage surrond.
PO may have screwed with things.

[needragr]

URGH!
OK so your LATE car has the wiring, my EARLY car does not. ...how does that help me?
I need some help.
How do I correctly manually wire this cluster for Tach operation ...and
How do I test the cluster fuel gauge for operation independent of a signal form the car?
Im confident of the wire path & sender operation up to the connector point under the dash.
If I had the wiring diagrams or Haynes manual I might be able to figure it out but I still dont understand why this had wires from the coil jumpered to screw posts on the back of the cluster? To energize the tach?

[ryanprins13]

Tach cluster into a L trim car

Did your tach work before you removed the cluster? On carberated cars its common to get your tach signal from the coil. If it was working that has to be what it was for. I cant help you with how to properly wire it as i am only familiar with the efi. But if it works and isnt going to start a fire i would leave it.
Speedo cable just needs to be greased.
What kind of signal does the fuel sender send to the gas guage? Is it 12v on full and less voltage lower? Is it 5v on full? Or is it based off resistance in the current? A haynes manual would be helpful to have... Someone sent me the complete wiring diagram for a festiva once ill see if i can find it.

Here:
.easternbeaver.com"]Eastern Beaver.

http://www.fordfestiva.com/forums/showpost.php?p=705704

Sent from my iPhone using Tapatalk

[nonamekid]

There were some 88-89 L models that did not have all the wiring for the optional items. All 90-93 L models had the extra wiring.

Gas gauge shouldn't be affected by the model. You either have a bad sending unit, a bad gauge cluster, or bad wiring between the 2 items. Test the sending unit at the fuel tank. Flip the rear seat up, pull the carpet back, unscrew the 4 screws for the inspection cover, and then remove the cover to get access to the top of your gas tank where your sending unit is. You can then pull the sending unit and test to see if it is working properly.

The tach is one wire and should be able to be added to the electrical connector for the instrument cluster.

[needragr]

So I revisited this as its kind of driving me crazy.
I pulled the R. seat. I had tested my sender previously & it showed a graduated resistance from top to bottom of the swing. ...Good.
I had also tested the continuity of the yellow (hot) wire from sender to the connector beneath the dash, so I pulled cluster and tested the continuity from the sender to the L. round cluster connector ...GOOD! I also tested the ground wire from sender to chassis and from the cluster connector to chassis & those were good...~!
So its looking like the gauge itself may be bad so I had a spare identical cluster and plugged it in and with .5 tank of gas STILL no indication at the gauge!!!! Something is up. :cry_smile:
As for the Tach It looks like I have directly wire it to the screw posts on the back of the cluster.

[tooldude]

It sounds like you have checked all the ground side of the cluster, but what about the B+ side? Check whether the meter fuse is blown and is getting B+. Check that the BK/Y wire terminal, which connects to the left side of the cluster, is receiving that B+ from the fuse. If that's good, disconnect the tach and see if the fuel & temp guages then work (because I'm not sure what you're saying about those wires). If not, there must be a problem in the cluster. Like nonamekid already said, there should be only one wire from tach to coil and it should be on the negative coil terminal. The guages actually could be checked with the cluster out of the car by connecting B+ and B- to the appropriate connectors and connecting resistors in place of the CTS (330 ohms) and fuel sending unit (33 ohms). Those values should put the guages around center. I don't know what wattage they would need to be without measurements - maybe 1W.

[needragr]

just thinking out loud, correct me, anyone, but I didn't think the gas tank probe "sends a signal" anywhere. It's a resistance to (chassis) ground (really a rheostat) read by an Ohmmeter (the fuel qty indicator)..no?
I would think if we could find an aftermarket sender (summit racing? ) you could wire a cheap rheostat (POT) in series with the fuel probe and indicator, and adjust the 'empty' side resistance however you want. Not much current involved here, so I wouldn't worry about heat build up.