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CarQuestionGuy, Technician
Category: Car
Satisfied Customers: 1259
Experience:  ASE Master Auto Technician for 5 years, ASE Refrigerant Handler, ASA, iATN
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two relays to control headlights and they work..parking..dash lights

Resolved Question:

I have a 78 Triumph Spitfire with an electrical problem I can't seem to figure out. I added two relays to control headlights and they work fine. But now I don't have brake, backup, sidemarker, parking, or dash lights. Also, my gas gauge, temp gauge, and tach do not work. Headlights and turn signals are fine. I have pulled all 3 fuses and they look fine. Engine runs great.......just no lights. Any suggestions???????
Submitted: 5 years ago.
Category: Car
Expert:  CarQuestionGuy replied 5 years ago.
Why did you install the 2 relays? Did this problem happen before you put the relays in?
Customer: replied 5 years ago.

all of my lights and gauges were operating after installing relays, except for one brake light and one license plate light. Changed both of the bulbs, then no brake lights at all. Did a continuity check on brake light switch and it was working properly. Then all my lights and gauges stopped working except head and turn signals.

I installed relays to take part of the load off the switch and give me brighter lights.

Expert:  CarQuestionGuy replied 5 years ago.
Spitfires were known for these types of electrical issues.
Since one brake light and one lp light were working we know that power was getting back there. Did you test the lights that weren't working to see if power was getting to them?
Have you traced the power in the wiring to see where it drops off?
Have you checked the grounds?
Customer: replied 5 years ago.
How do I go about tracing the power in the circuit? I have a multimeter but not a lot of experience using it. The grounds in the front of the car are all hooked to the main which runs directly to the negative post on the battery. I have complete circuits for the head lights and they are grounded to the main so all the lights should be grounded.
Expert:  CarQuestionGuy replied 5 years ago.
Ok. Just set the multimeter to measure about 12 volts (there is usually a 20 volt range on the meter) then with someone stepping on the brake go back and see if there is power to where the brake lights go. Read the voltage. If there is not, then go back to the brake pedal switch. See if there is power on either side of it. If there is power going to it but not out of it (to the brake lights) then the switch has a problem. If there is no power to the switch then check for power at the fuse block. If there is not power there then check from the fuse block all the way to the battery.
Be careful when you are checking all of these things that you have a good connection with your multimeter both with the lead that connects to ground and with the one that you are testing the power with.
They have a lead for multimeters called a "bed of nails" that makes wires really easy to test. It just clips onto the wires and pierces them, but when you take it off it doesn't leave holes in the wire.
This testing method is going to be your best bet to trace down this problem. I think you probably have a bad connection somewhere, but the trick is to trace it down.
Do some testing then let me know what you find and I can help you more.
Customer: replied 5 years ago.
will try all these things in the morning and get back to you. If this get me back on the road again, the fee will definitely be worthwhile. to you in the morning.
Expert:  CarQuestionGuy replied 5 years ago.
I will be online tomorrow evening so I will try to connect with you then. I'll do my best to get you back on the road.
Expert:  CarQuestionGuy replied 5 years ago.
Just checking to see how testing went today. Let me know and I'll give you some more direction if you need it.
Customer: replied 5 years ago.

I couldn't trace the reason for the brake lights not working. The back-up lights and brake lights are on the same circuit. I got all the other lights functioning. I tapped into an "always hot" circuit and ran a fused wire directly to the brake lights. The only problem I am still working on is the tach, gas gauge, and temp gauge are not working. I think that problem is caused by the voltage stabilizer. Could be not grounded properly or a loose wire because sometimes they work and sometimes they don't. I know those stabilizers have always been a problem. Can they be bypassed?

Expert:  CarQuestionGuy replied 5 years ago.
There is really no way to bypass them. Here is a way that you can test it though:

To test the stabilizer get an analog (the old style with a needle) voltmeter and open the center section of the dash. Pull the green wire that attaches to the fuel gauge, and attach your positive lead there, ground the negative lead, and turn on the ignition. If you are measuring 10 volts constant, then the voltage stabilizer is fine. If not check that is is properly grounding. Make sure the screw is tight where it mounts. Check that all contacts are clean and tight.

Let me know what you find after this test. It probably is being caused by something that is loose or not grounded properly. Sometimes I use a wire brush and clean the metal where wires are grounded to make sure they are getting a good ground.

I'll help you more after you test this.
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