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Ammeter

Ammeter

To all, What might the problem be when the amp guage needle is deflected full positive (to the right)? It only happens sometimes. Also, the instrument lights and right turn signal quit working about the same time. Any possible relation or common thread between the three? Thanks. - Aloha, Rob XK-140 FHC

Rob, When you first turn the key on and do not have the engine running, that is the generator is not running, does the amp needle go positive or negetive. I ask the question because I suspect you have the amp meter hooked up wrong. I know I have not answered your question yet but checking this may give us a clue. - Neville Laing

Rob -

You've a temporary or intermittant short! You could try to isolate the offending circuit by disconnecting the instrument lights, etc., circuit by circuit (also check the panel illumination rheostat - a scrap of wire or other such conductor might have achieved 'closure' between it and the back of the instrument panel. This is serious, as it could precipitate a fire!

I had a similar intermittant on my old XK-140 DHC - once a month or two the taillights went out (blown fuse). By a proces of limination (divide and conquor) I isolated it to the wire harness that runs through the body up inside the left rear. Couldn't get at the offender to replace it (believe some of the insulation had rubbed away). Solved the problem with a piece of 1/4" drill rod in place of the oft-blowing fuse! Not recommended, but I was lucky! No fire!

Good luck, and have a happy and safe Fourth of July! - Larry Schear Twin Cam, Inc.

1.My input on this problem is that occsasionally your regulator is sticking causing a full charge into your battery. This isn't particularly healthy to the battery.

2. When your panel and right turn signal lights went out, I suspect two different problems (as I have had both happen to me). The turn signal can be the Lucas box of interrupter coils for both turnsignals (I forget the exact name of the box . The blinker canister you buy at your auto parts store gets its power from this Lucas Box. It can also be a broken wire at the end of the your steering column (or in the steering column). Use your ohm meter to determine that you are getting continuity to the Lucas Box of coils. As to the panel lights, connect alligator clips across the two terminals on the rheostat for the panel lights. If the lights work, make the jumper wire permanent and forget the rheostat. If they don't work, ascertain whether you have power at the rheostat with a voltmeter and work backwards to find where a loss of power can be. - Steve McDonald '53 XK120 S673352

I agree - I've also had the sudden, intermittent pegging-to-the-max of the ammeter happen with Chrysler products (70's and early 80's) when the solid-state external regulator is on its way out. Another symptom, generally occurring first, with these vehicles is a noticeable fluctuation in headlight brightness.

At least with the Lucas regulator, it has points which can generally be cleaned-up enough to usefully extend its life !! - Dave Quirt

I guess that I'll put my two cents in also: A sticking regulator can cause the generator to burn out its armature. Then you have to hassle with getting the armature redone or find another generator. Neither option is all that cheap! (I know from experience!) - Cleo Bay XK120, XK140

Rob, Regarding your gauge anomaly...

although this has not happended on myXK 150, I have a 59 Sunbeam Rapier, which has a grounded metal backing plate behind the 4 guage cluster in the center of the dash. This plate is the common ground point for water, amps and fuel. Occasionally the fuel and water needles would run in tandem, that is, when the fuel gauge read half full when I knew that I had a full tank, I would tap on it and it would go to the correct 'full' reading. At this point, the temp gauge would then move to a higher, and supposedly correct reading.

Additionally, my fuel gauge would 'spike' to the right when I turned on the headlights. Tapping on the gauge would return it to normal.

The solution...acknowledging that this looked every bit like a bad ground, removed all gauges, made sure they were all grounded while at the same time isolated from one another,cleaned and reconnected all of the braided wire ends,and tightly secured the brass finger nuts which hold the gauge posts in place against the backing plate. No problems since then. - Bill Burke

Aloha, Rob. Did you give the engine block a good thorough flushing with the garden hose while you had the radiator out? I would say remove the block drain petcock and all hoses when you do this. What about that heater hose, is it routed in and out of the correct manifold ports? (irrelevant question if you have only two ports of course). Is it common in Hawaii to run without antifreeze? Here in Illinois we use a 50% solution, it helps keep down the rust buildup. Prestone and Peak are common brands here, both claim to be fine with aluminum and I haven't had any problem with all the various aluminum head cars I've owned. Change it every couple of years. Also a very unusual but nevertheless possible failure mode is broken vanes in the water pump impellor (happened to me on an E-type).

Ammeter pegging positive suggests to me the voltage regulator is not cutting out. Clean the contact points by dragging a strip of sandpaper through them. Do not touch the adjustment screws, they were set by Lucas and are presumably still correct. Someone on this list a couple of months back suggested soldering all the riveted connections on the backside of the regulator, and I did this recently with good success. Failure of lighting circuits is an open circuit, likely a dirty connection, perhaps the fuse clips. Good luck. - Rob Reilly

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