SV Electrical Issues

[Henry K]

Okay, at the outset I will admit that I am electrically-challenged. I have a ’67 Alpine SV with a number of electrical issues, some of which I’ve solved and some I have not. The PO did some interesting re-wiring and I’m working through those issues. However, I have 2 for which I’m seeking your help. They may be related.

1. The fuel gauge doesn’t work. I’ve checked the continuity from the sending unit into the gauge (it’s fine) and I’ve checked power to the sending unit (it’s there) and I’ve checked the gauge itself (it works). Thus, I think the issue lies with the sending unit itself or the ground. I just don’t know where to check the ground. So, how should I test the ground for the fuel gauge?

2. My brake lights are funky. When the running lights/head lights switch is off, the brake lights illuminate very faintly. (I have installed a new pressure switch.) When I switch on either the running lights or head lights at the dash, the rear running lights illuminate very brightly, but the rear lights only very faintly, barely perceptibly, get brighter when depressing the brake pedal. Not nearly enough for safe street driving. I’ve tried swapping the wiring around under the dash at the light switch, with no results. Therefore, I think it MAY be a grounding issue. I don’t know how I should begin to track that down. It MAY be inter-related to the fuel gauge issue but I’m not sure. While the PO had re-wired some things, this doesn’t seem to be part of that. How would I check the ground for the brake lights?

I also have an issue with the horns, which are barely audible. I know I said I have 2 issues, but I thought I’d toss in a bonus issue too, just as an added extra.

I would appreciate some guidance on tracking down these problems. Thanks in advance for any assistance.

Henry

 

[Ragg Mopp]

Can't help you with the fuel gauge but I did have the same problem with my tail lights. The problem is probably at the back. The wires to the lights are crossed and when you hit the brakes, the running light side is coming on which is about 5 watts vs the 20 watt brake light. Just reach in behind the gas tank and you will find one light that has two wires attached. Switch them and see if the problem goes away. You will have to do it on both sides. If that works but your license plate light now comes on when you hit the brakes, the problem is at the junction under the dash where the lights split and wires go to the back. It is behind and to the top of the left kick panel. You can match the wire colors from the tail light connections but if they are painted at the tail and you can't tell, you will need to match the colors from the wiring diagram.

 

[Henry K]

Thanks, Greg. I appreciate your quick reply. I will try that immediately.

Henry

 

[mattinoz]

Hi Henry,
I think your issue may well be grounding of the tail light assemblys. The factory grounding (earthing) of these unit relys on the screw fixings to the body. Many have attached a dedicated wire from the light unit to a solid ground on the body thus making grounding thru the fixing screws obsolete.

In order to test the ground you should get yourself a basic multimeter. These are invaluable in tracing all sorts of electrical issues such as the grounding of your fuel gauge. Here the gauge body should be grounded via the earth loop that goes past all the gauges.

While your at it check the grounding of the main earth cable from the battery. If I remember correctly it attaches to the body at the battery box. Removed this and clean the contact surfaces to ensure the grounding is good at this point. If it's not then chasing other possible grounding issues may well be a waste of time.

 

[Tom H]

Henry,

Your expressed lack of electrical understanding causes me to doubt some of the tests you've already done. Like how did you check the continuity from Sender to the gauge?

So here's what I suggest; all done with a voltmeter.
1) with the ignition on connect the black (-) lead of your voltmeter to ground - the chassis anywhere - find a screw that goes into the body somewhere.
2) Touch the red ( + ) probe to either one of the 2 terminals (not the lamp) on the gauge.
3) Then measure the volatge at other terminal
4) On one terminal it should read some voltage about 12 V but be going On /OFF about 2 times per second if the voltage stabilizer is working.
5) on the other terminal the voltage should be about about half that , depending on how much gas is in the tank.
6) If there is never any voltage on either terminal, you have no power applied- must be a broken wire from the volatge stabilizer (assuming the Temp gauge works)
7) if the voltage at both terminals is about the same, you have either no connection to the sender, or the sender is not grounded.
8) Assuming you find the volatge the same on both termninals , go measure the voltage at the sender - accessed via inside the trunk. Measure the voltage on the terminal on the sender. If it is again the same as found at the gauge, then you have a grounding problem at the sender. I think it's grounded inside and you'll need to take the sender out of the tank.


Good luck. I'll check for your reply in a couple hours.

Tom

 

[Jim in PA]

electrical

Be sure all connectors are clean and tight. I had similar issues with brake lights and it was due to a loose spade connection at the double connector tail light. Scuff the connections with Scotchbrite if you can or even a slip or rolled tube of fine sandpaper. Use pliers to gently squeeze the female part of connectors so they slide together tightly.
The bulbs should be cleaned as well as the inside of the bulb sockets. I had many issues so I went the full monty with cleaning and tightening connectors. I even bought the bullet connectors and the tool for crimping and an assortment of splicing connectors. Many flaws found and resolved...

 

[Henry K]

Thanks to all who responded. The fix for the brake light problem was as Greg suggested, ie switching the wires at the tail light. I did a lot of other stuff but hadn't previously tried that since it looked to me that the PO hadn't fooled around with that area. (I was wrong.) BTW, I had been using a multi-meter for my testing.

Thanks again for the help and suggestions. I appreciate and am truly humbled by the collective wisdom in this group.

Henry