I finally got around to testing the wiring and temp gauge. There is continuity between the sender and the gauge. Performed the test below and saw no movement. Just for fun I connected the gauge directly to the battery and it moved right across. So it appears the gauge has life in it still. Now I'm guessing the wire to the stabilizer is bad or disconnected. I get no voltage at the terminal with the ignition on.

What's the best way to get at the stabilizer? Not sure where it is.

A reply from David Crowne... (in blue)

Medland will sell you a new one for under $30. Keri Meyer will do a little better than that: $22. That's K&D part no. N15/13-CT897.13 - CT897 Part N15/13 - CT897 On the temp gauge, the light green wire goes to the voltage regulator and the green/blue wire goes to the temp. sender (via a myriad of intermediate connections, natch).

To test your gauge, make sure the ignition switch is on and that there is contact between the light green wire on the gauge and the terminal of the voltage stabilizer to which the light green wire that goes to the fuel gauge is also connected. When you ground the green/blue wire, the needle of the gauge should move all the way to the right (i.e., maximum temp. reading). When the green/blue wire is not grounded (waving freely in the breeze produced by your sighs), the needle of the gauge should be all the way to the left (i.e., as cold as cold can be). You can also test for accuracy (ask me how), but the test just described will at least tell you if the gauge works. Testing for accuracy requires at least this minimum functioning, of course.

The voltage stabilizer lives the compartment behind the little panel just forward of your left knee on the lower part of the dash panel. You remove that panel by pressing in the little knob and turning it about 90 degrees; the panel then comes right off, revealing compartment containing a significant part of the car's neural network. The voltage stabilizer is in there, up behind a rat's nest of wires. It is a more or less rectangular object with rounded corners, somewhat silver-ish in color (cadmium plated but probably dull with age), and about 3/4" X 1-1/2" in size. It is held in place (and, please note, grounded) by a sheet metal screw that goes through a tab on one side of the wee rectangle and into the metal of the body. I mention the grounding because, after the fiddly job of removing it, one might be tempted to simply let it hang free among the other wires; but it needs the ground or it won't operate at all.

You haven't said if, along with your temp gauge, your fuel gauge is also inoperative, and also with no voltage to the light green wire that connects to the back of the gauge. If so, look to the voltage stabilizer, because both the temp and fuel gauges (and nothing else) are fed through the voltage stabilizer. But before just replacing it, check to see that the voltage stabilizer is receiving 12 volts through the green wire that runs from the tachometer to the stabilizer and that it is properly grounded through the mounting screw. If the fuel gauge checks out OK, I'd guess that there's simply a wire loose between the stabilizer and your temp gauge.

Do let us know how (please note that I do not say "if") it all works out.
David Crowne in San Diego

Me again...

I'm officially confused and baffled.

I can get a response from my temp gauge by connecting each terminal directly to the battery. I have a good connection between the voltage stabilizer and the contact at the gauge. I have a good ground with the illumination circuit. I have a good connection between the new sender (from K&D) and the gauge. Still nothing registering.

The connection at the voltage stabilizer to the gauges is the one at the right/passenger side if that helps. Both the fuel gauge and the temp gauge are fed off the same contact. Two wires fed into a female spade connector. If I disconnect that, the fuel gauge goes dead so I know there's something working there.

I connected one terminal on the gauge to the stabilizer and the other to the sender. I grounded the gauge housing and tested for voltage. With the car running, I saw 9.7 volts at each terminal. That sounds a little strange to me. Take the ground away and nothing.

Are both gauges supposed to be connected to the same terminal on the stabilizer?

What am I missing here? Do you suppose my gauge is really dead and only responds to 12 volts?

David again...

For your benefit (?) I just went out into my garage and measured the resistance of my temp gauge sender, with the engine cooled down to perhaps 75 degrees F. I got a reading of .564 ohm. My temp gauge seems to be quite accurate. No, let me re-phrase that. It never tells me the coolant is boiling when it's not, or tells me the coolant isn't boiling when it could be (though the latter condition has never happened with my relatively cool-running 383), so I trust it. Anyway, the readings on the gauge correspond to what I think they should be with the 180 degree thermostat I'm using.

Both the fuel gauge and the temp gauge SHOULD be connected to the same terminal of the voltage stabilizer, as you say they are. Feeding temp gauges and fuel gauges with a voltage stabilizer was common British practice in the era when our cars were produced. I suppose the theory was that surges in voltage when the alternator was doing its utmost would produce falsely high readings at the temp and fuel gauges. Dunno. Anyway, the stabilizer is intended to produce a more or less constant 10 volts or so, and yours is not far from the bullseye on that score. So you run 10 or so volts through the temp gauge and on to the sending unit, which introduces resistance that varies with the temperature of the coolant in the engine. I don't know enough about electrical devices to suggest the idea with much confidence, but it may be that the gauge is sensitive to polarity. Well, not polarity, exactly, but that the "crossed coil" construction of the gauge may require that one particular connection must run to the voltage stabilizer and the other to the sending unit, and not vice versa. Try swapping the connections and grounding the wire to sender and see if that gets a rise out of the needle.

April 17 2004
Today I went out for a spin and had some pretty bad episodes of cutting out. No matter what speed. Mostly on deceleration. Gravity/inertia? The tach and the engine go dead, just stop. With the engine still turning, applying gas will get it going sometimes. Other times I have to crank the engine. Starts right off. No trouble there. I think there must be some sort of wire finally worn through somewhere. Will have to go over all the ignition wires.

Your cutting-out problem does sound like what you'd get with a bad connection in the ignition circuit. Perhaps, however, it's in the ignition switch itself? Looking at your web log, I see that you have had similar problems both before and after the installation of the electronic ignition distributor, etc., and with the same kind of symptoms; that is, the engine quits, but will fire (and backfire) when you try to re-start it, or will not do anything, or will simply start as it should and run OK for an indefinite time. That kind of behavior is typical for a failing electronic control unit, but your ECU is, I believe, too new to call much suspicion down upon itself. Our ignition switches DO fail, though my experience of that was mainly a failure of the contact for the starter. But the erratic and intermittent nature of the fault you're experiencing with your ignition does sound to me like worn and/or burnt contacts in the switch, which maybe make better contact when you twiddle the switch to start the car, or maybe don't. If you replace the switch, you don't have to replace the lock and all; only the switch itself, which is somewhat loosely attached to the back of the lock. Dear Keri has the switches in stock, I believe. If it has never been replaced before, it might not be a bad idea just to go ahead and put in a new one. Then at least you'll pretty much KNOW that the trouble isn't caused by the switch.

Waiting breathlessly for news of miracle cures,
David

Last weekend I tried to pretty up the boot spring/latch mechanism. The previous owner had a spring and boot affair that had finally started to look ugly. I took that all apart and put it back as I though t it should be. Now the boot won't "pop" open when released. I'll have to get some sort of rubber bumper as listed in the parts manual.