Instrument cluster
 

Have any of you removed the instrument cluster from an "88 FC? I've got mine out but can't get the male part of the wiring connector far enough out of the body to examine the wires. I'm pretty sure there's a short in the wire between the oil pressure gauge and the sensing unit. The cluster is completely removed.

Dennis, what exactly are you asking? The only question you've posed is has anyone removed their cluster, and the answer is yet :)

The large electrical connector on the cluster plugs into a "socket" under the dash. I can't pull this socket out to get to its wires. It's fastened to a piece of sheet metal with a black plastic fastener. Do you know how to free this connector/socket enough to pull it out a few inches?

Those fasteners are difficult to remove without damage, unless you "pinch" them from the underside. Easiest way is to use a tool called a crow's foot. It's basically a forked pry tool.

The plugs also can disengage from the fasteners by sliding them apart, but that's very challenging when you're short on space.

Oil Pressure Gauge
 

OK, the wire between the gauge and the sending unit appears to be shorted out (somewhere.) That would account for the pegged high reading, wouldn't it? If all my assumptions are correct will it be easier to bypass this wire with another new wire, not in the harness?

Hold on a second. Poke around under the hood. There originally was a large filtering capacitor on this circuit. After 25 years the caps usually go missing, and the dangling connectors are sometimes mistaken for ground wires.

I think the oil pressure wire is Yw/Rd? Look for a Yw/Rd wire with a single pin connector and see if the cap is still connected, or missing and the wire grounded.

Oil Pressure Gauge
 

Here's what I've found: There is a single y/r wire attached to the sending unit with no capacitor in view. That wire runs into a large harness about 6 " from the sender. My diagram shows a condenser in parallel with the y/r wire but gives no clue to its location. The condenser is not in the path to the gauge. It's attached (somewhere) to y/r wire and to a ground on the other pole. Do you recall what the condenser looks like? Also the post on the sender is a short wire or rod with a ball on the end. The connector on the wire has a cross section like this :0_0. Do you know what I mean? The connector just slides over the ball on the sender, which seems strange.

All you're describing is correct.

The condenser (old school terminology for capacitor) is in parallel to bypass noise on the circuit. There is one for the oil pressure gauge, and one for the ignition. They're small black rectangles with a ground tab for mounting. Stock, one was located on/around the slave cylinder on the trans, the other was on the driver's side fender area. After all these years, they tend to move/break/disappear.

The connector for the pressure sensor is quite strange, I've never seen similar on another vehicle.


Edit: Example of condenser. The one on the FC has a white connector IIRC.
Attachment 596209

Oil Pressure Gauge
 

I can't find a condenser, a loose wire or even an empty screw hole anywhere in the engine bay. I did find what I think is a y/r wire in a harness running down in the direction of the tranny but I have no way of seeing under the car. I'm thinking about running a wire through the speedo cable grommet and attaching it to the y/r fitting going into the socket / connector. I would also branch off this wire in the engine bay and connect a condenser which I can mount to the firewall. I could avoid removing the dash board and /or working under the car. The run from the sending unit to the speedo cable is only a few inches so I can make it look pretty original. Doing this I would bypass any shorts or the old condenser. ???? BTW I'm very impressed with your knowledge and appreciate all the time you're spending on MY problem.

Dennis

Dennis, that's why we are a community, to help each other :)

Your idea will work. The signal only goes to the gauge; as long as the sender and gauge are isolated from the faulty wiring, you should be good. As a sanity check I'd test this and just loop a wire out the window and to the sender as a test first. The condenser isn't imperative, but it's nice to have on there to reduce jitter on the gauge. If it were me I'd still see exactly where that Yw/Rd near the trans is going and use the factory wiring.

Oil Pressure Gauge
 

I've got the gauge in and working. I used my bypass method but left things in place so I can use the factory wiring when I can get under the car. I would not have been able to do this without your help. Thank you very much.

Dennis

Glad to hear, nice work :icon_tup: