Something behind center instrument cluster let out its smoke

[cdscds1 (cdscds)]

Hello all,

It has been quite hot here in LA today but on the drive home on the freeway with all the windows open,
A wisp of smoke appeared in front of the voltage/oil pressure/clock/water temperature/gas gauge
Cluster and I watched all the needles go to zero over the span of a minute.

She got home all right after I pulled off the road to check for any burnt wires or what not.

All fuses seem fine and have continuity,

two things seemed out of place;

This guy which I know as a suppressor of some variety is not connected on one end.

There’s one on the left side of all of this and one in each of the fuel pumps.

The other suspect is this object which I think regulates the voltage to the cluster.

Checked continuity on the green and red wires that come from this to the cluster, checks good.

Likely suspects? Or is there a mystery fuse somewhere?

Thanks everyone!

[Robert_Wilkinson]

@cdscds1

I watched all the needles go to zero over the span of a minute.

Yes, the Series 1’s do leak a bit of smoke now and then, but you can go quite a while before a refill is necessary.

The IVR is a likely suspect, but the voltmeter and oil pressure gauges would be spared–only fuel and temp would stop working. If ALL gauges went to zero, there was a much broader power loss. I would jiggle all of the connectors on the center panel; including removing and reinserting the large connector at bottom. Not clear from your post, but if the gauges still aren’t registering it should be easy to find the problem.

The “suppressor” is a capacitor that is supposed to be connected between the IVR output and ground. Its purpose is to reduce noise that would be audible when listening to AM radio. You can remove it. IMHO.

[MLee (Mark Lee (Pay Pal Patron))]

Good to know, since I recently acquired a Series I; What’s an IVR?

[godfrey (Jag-ur)]

Moss Motors used to have a supply of NOS Lucas wiring smoke available to refill your system… getting harder to find and the Chinese copies just don’t seem to work

[Robert_Wilkinson]

@MLee

What’s an IVR?

Mark, it’s the Instrument Voltage Regulator or " this object which I think regulates the voltage to the cluster" as described and shown in the photo above. Much info in the E-type and XJ archives. Only supplies the fuel and temp gauges. OP gauge has one built into the sender; clock doesn’t need voltage regulation; voltmeter obviously doesn’t want voltage regulation.

[cdscds1 (cdscds)]

Hello all,

Robert_Wilkinson thank you for your suggestion!
You were right that something beyond the IVR was at fault!

Took the IVR out and bench tested it first for shorts (none) and then voltage with my DC power supply, “B” input connection at 12V “I” output to Instruments all over the show, but since it’s a Bimetal Circuit that goes on and off all the time and my Multimeter is not the best in the land I figured that was ok., mostly 10 ish volts.

Power on the car however was not happening, nothing at either “B” or “I” connections… telling, but one must be systematic or your just in for lots of frustration when your trying to sort out electrics.

Next was testing voltage to the plug

Red wire white tracer (light circuit)was fine.

Then check continuity on the wires from the IVR to the printed circuit again, all good, not pretty but good.

Blown away by the somewhat cheap nature of the printed circuit, it’s not a proper board on some sort of phenolic or glass fibre, it’s on some flimsy plastic sheet.

Checked the continuity as best I could on the car and then I noticed the classic signs of an overheated piece of copper in a circuit board lifting up and out due to overload/overheat!

So I unscrewed the board and instruments via:
6 screws that connect the printed circuit and the instrument innards to the housing binnacle.
The green and red wires to the IVR,
The nut and flat blades screw to the clock,
Finally the wire from the voltmeter to the ceramic resistor housing that has no resistor!

Now let’s see if we can solder in a wire across this

Cleaned the copper leads with some alcohol and used a piece of scrap glass fibre circuit board from another project underneath to protect the printed circuit from melting.

Out comes the Hako and I tin one side.

I grabbed a lead off of a 9V battery connector, close enough?

One wire connected, not my proudest moment in soldering!

The other side has plenty of real estate to tin.

And the wire was tinned and quick to connect to the copper strip.

Used a piece of electrical tape (white was all I had handy and wrapped it up.

Added another piece of tape on top for good measure.

Put it all back in and then turned it on to make sure no more smoke escaped!

All seems to be working now, better hit the Chevron before I go to work in the morning!

The only thing left to ask is if this bodge is good enough?!?! I’ll keep checking on it throughout the week, but I’m wondering if I need to think about a new solid state IVR.

Or miracles of miracles this printed circuit sheet is still available?

Once again I get to see the voltage seem to low,
The oils pressure fluctuate to scary lows,
The clock forever at 12:19:12.5,
The temperature gauge that terrorizes me every summer!
And the gas tank that always seems to be on “E”

Thanks again for all the help, case closed for now!

P.S Godfrey, I have found L.A. smog is an excellent and highly concentrated replacement for Lucas smoke!

[Frank_Andersen]

@cdscds1

The temperature gauge that terrorizes me every summer!
And the gas tank that always seems to be on “E”

**
You’re not the only one looking at the temp gauge apprehensively…

The ‘empty’ tank reading is not related to the voltage stabiliser anyway. As a matter of fact, the stabiliser was later omitted, with seemingly no ill effects - these instruments were never high precision…

Frank
xj6 85 Sob Europe (UK/NZ)
**

[Demian]

Outstanding work. Well done.
Thanks for posting and updating.
Great stuff.

Gotta say, within all forums I’ve perused over the years, I’ve seen no greater competence of workmanship, wherewithal, and downright craziness as Jaguar enthusiasts!

Edit: PS, i just had to add, this is something i completely would have overlooked btw. Really good to know.

[MLee (Mark Lee (Pay Pal Patron))]

I haven’t gotten to my Series I yet Lord! I hope this isn’t what I have to look forward to. Reworking PCB’s ugh.

Good information though! Thanks

[Jochen_Glockner (Jochen Glöckner)]

Cdscds (ahmm … names make friendliness easier:-),

very nice job and no bodge at all, I’d say. Better than waiting for a replacement part anyway. That being said I’d give it just as much time of useful service as any “temporary fix”: about as long as the rest of the car!

10V is exactly right for the voltage stabilizer, BTW. Maybe I’m wrong but I thought the voltage stabilizer was only omitted with the advent of a different instrument type on SIII cars. For SI and II it should be there and yours is performing fine.

Water temp guages are critical these summer days. Your needle seems to sit in the perfect spot for me. Fuel guage empty on both tanks should be the instrument circuit. Do you have proper ground? The clock is a piece of fine mechanics. Somewhere I’ve read a how-to for overhaul. Oil pressure low on hot engine and idle? Welcome to the club! No need to worry though if your idiot light functions properly. The OP guage isn’t very good at correctly depicting low pressures.

Keep up the great work and the cat on the road

Jochen

75 XJ6L 4.2 auto (UK spec)

[godfrey (Jag-ur)]

[cdscds1 (cdscds)]

Sorry Jochen,

My name is Carl, but since there already is a Carl on the forum I used my initials, which I often go by in life

It’s doubled because I think at one point when I owned my first series 1 I must have forgotten the password.

[75jaggy (Michael)]

Replacement wiring harness smoke? Don’t buy it. It’s like a lot of the Lucas equipment, extremely difficult to make it work properly.