88 XJS v12 coolant temp gauge and oil pressure gauge not moving

88 XJS v12 coupe…my car starts and runs fine…recently the coolant temp gauge and the oil pressure gauge at the center cluster not moving at all…however all other gauges working just fine…I tried shorting to ground both the wire/spade connectors at the coolant gauge sensor/sender (passenger-side water rail) and the oil pressure gauge sensor/sender (inside the V at the rear near the fire wall) but still get no movement at the center gauge cluster…is there a connector block along the wiring harness i should check???..please help???

Lead,
Many of us have experienced instrument cluster abnormalities and fixed them. You need to remove the instrument cluster from the car and clean up the flexiboard contacts. It is also a good idea to add an additional ground wire.

There are lots of posts in the archives about problems with the instrument cluster and what people did to resolve them. While I had the instrument cluster of my wife’s 1990 XJ-S convertible out to fix a flaky tachometer problem I added a new ground wire and wired up the unused green “caravan” warning light to come on whenever the auxiliary cooling fan comes on to give provide confirmation that the cooling system was working as it should. I have had relay and thermostat problems in the past and the auxiliary cooling fan did not come on when it should have. I also removed the green filters over the light bulbs to brighten up the instruments at night because my wife complained that she couldn’t read the instruments at night.

If you haven’t already done so I recommend that you download Kirby Palm’s excellent “Experience in a Book” from Jag-Lovers (it is free) and read up on instrument cluster fixes and other matters that you will find very helpful. The archives also has a wealth of information about this.

Paul

Usual problem with bad contacts inside instrumen cluster. I had to disassemble my cluster completely to clean all connectons and that cured all now all the gauges work as never before :slight_smile: you have to clean not only the flexiboard contacts but also there may be bad contacts inside the cluster.

The addition of a new earth worked wonders for my cluster.Dan

thanks to all your assistance and suggestions…it turned out to be electrical contact corrosion buildup at the wiring harness (CF6) connector… I unplugged the CF6 block connector…cleaned up all the contacts…re-plugged it back in …turned on the ignition switch…checked for 5V at both the coolant temp and oil pressure spade connectors…started the car…both gauges came back alive again.

I’m not familiar with the connector numbers. Is this the bulkhead connector where the harness passes from behind the right front wheel into the passenger side footwell? Just curious.

this connector is located inside the engine compartment on the main wiring harness that is strapped along the passenger side fender support brace-bar leading towards the rear of the engine…the large (CF6) engine connector block is square and services seven wires that runs into the engine…the connector block in my 88 car is located near the vicinity of the auto transmission dipstick area strapped to the fender support brace bar.

No such connector on my '76. Might be equivalent to the one on the center firewall on my car… very difficult to get at, BTW.

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Yes, I’m sure we’re talking about the same connector now. Strange that the diagram seems to show it about where mine, i.e., center firewall area. It has given me much grief over the years, most recently with regard to ignition wires. One day I’ll rip it out and replace it with WeatherPack connectors.

Hmm, I think there might be some confusion here, or at least big differences between the wiring configurations of model years.
When I cleaned up the engine bay of my wife’s 1990 XJ-S convertible I cleaned up and repaired the wires to the CF6 connector. It is an overly large black cylinder shaped connector for the three wires leading to it from sensors and going on to the instrument panel. The wires are Green-Blue (GU) for the Coolant Temperature Gauge, White-Brown (WN) for the Oil Pressure Gauge, and White-Slate-Blue (WSU) for the tachometer. The CF6 connector is hidden from view in my wife’s XJ-S because is located close to the firewall beneath the fuel rail just aft and to the left of the throttle pedestal. It is difficult to access unless you remove a lot of stuff, lije I did to clean up the engine bay.

Lead, can you post a picture of the CF6 connector in your car?

Paul

This kind of connector is all over the early XJS. Don’t know when, but as you point out they changed. Today, these molded rubber bullet connectors are commonly called “trailer” connectors.

my 88 (CF6) connector looks exactly like ed’s “trailer” connector pictured above…

My 83 Right-hand drive V12 gauges plus the other 2 (fuel level and voltage) have just stopped too (all pointers at bottom).
I have checked all 12 under scuttle fuses and the 5 under-hood on the passenger side inside wing (any information on what circuits those 5 protect would be welcome as the cover is missing). I think I have found the CF6 connector (driver side near firewall but haven’t tried to fettle that). I also removed the instrument cluster from the fascia and had a look behind there without moving it past the steering wheel (but haven’t disconnected any wiring there as yet).
Any advice on where and what it would be most profitable to check first would be very welcome!
Edited; I have now had the CF6 connector apart and cleaned but it made no difference.

A while back I bought a used HE instrument cluster to replace the one in my 1979 coupe. I needed to do that since fitting a 5 speed manual box with a pulse output negated using the original mechanical speedo drive.
There were all the usual dramas overcoming the problems with the flexible printed circuit board to get it all working. To help it along and make a record for posterity I drew up a diagram with all the info on the electrical connections on the flex, the wire colours to the connectors and how to check the gauges are working. It shows the layout you would see looking at the back of the cluster so troubleshooting is a breeze, well as breezy as anything could ever be on the XJ-S electricals.

The diagram is in .pdf format. If Ed Sowel likes to add it to his website it would be easy to access for dealing with instrument problems.

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Richard,
If Ed is unable to add your wiring diagram I would be happy to add it on to my website

Bernard Embden

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Hope you two combine successfully on this!

There would be no downside to having it at both sites. Send it to both of us, Richard.

BTW, there is already an extensive write-up on this gauge at my site.

Richard / Ed

I received and have published Richard’s XJS cluster wiring diagram on my website.
Richard, I decided to convert the pdf file to jpeg. I had some issues with optimizing the file to what I considered small enough. Internet connections vary worldwide. Although adobe reader is almost universal there are still issues with having the latest versions. The jpeg file can be opened with a number of programs.
There is a small loss of resolution but not noticeable unless one had your original file in hand.

The link is:
http://bernardembden.com/xjs/xjscluster/index.htm

Thanks again for making this available.

Bernard

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The following link from my upgrade to an electronic speedometer might also be of help.
The link is:
http://bernardembden.com/xjs/speedup/index.htm