Electrical short

[Zipppo 11]

I turned on my headlights last night in my 1970 sportsroof and both healights burnt out, dash lights quit, blinkers in dash cluster do not light up yet the blink and fuel gauge reads empty. I was told that it was the headlight switch shorted out and needs to be replaced. Does that make sense almost sounds to simple or should I be looking deeper?

Thanks in advance

[LindenBruce 27]

Did you blow any fuses? If everything quit at the same time it's possible it is the headlight switch. I don't know why the fuel gauge would be effected thought? B.

[Raven R code 281]

You can also pull your dash and look at the circuit board on the back of your cluster. The corners of mine had delaminated then curled (over time) and ended up shorting both fuel and temp gages......not to mention it melted my gage faces too. Going to do a full resto on all Gage's and clock.

[Zipppo 11]

I will try the headlight switch first and see. Pretty basic and if it looks toasted then maybe that is it. I also will pull the dash and look at the circut board as well. Fuel gauge well maybe coincintal the sender went out.

[det0326 179]

I turned on my headlights last night in my 1970 sportsroof and both healights burnt out, dash lights quit, blinkers in dash cluster do not light up yet the blink and fuel gauge reads empty. I was told that it was the headlight switch shorted out and needs to be replaced. Does that make sense almost sounds to simple or should I be looking deeper?

Thanks in advance

 

Did the headlights actually burn out or just go out from lack of power ?

Dave

[Zipppo 11]

Both headlight bulbs actually burned out at the same time and none of the running lights work either. The dash lights quit working as well as the blinker arrow in the dash cluster.

 

The brake lights, interior lights horn and radio still work.

[det0326 179]

Both headlight bulbs actually burned out at the same time and none of the running lights work either. The dash lights quit working as well as the blinker arrow in the dash cluster.

 

The brake lights, interior lights horn and radio still work.

 

If the car was running when the headlights burned out you may want to check voltage at battery terminals with car running to see if alternator is overcharging. Just a thought

Dave

[Max Power 74]

Yup, actually sounds like maybe the voltage regulator quit regulating. Alternators can't really overcharge, they all produce an amount of voltage/currant that needs to be regulated, even the lowest rated ones. Alternator output never increases. Regulators sure can fail though.

[det0326 179]

Yup, actually sounds like maybe the voltage regulator quit regulating. Alternators can't really overcharge, they all produce an amount of voltage/currant that needs to be regulated, even the lowest rated ones. Alternator output never increases. Regulators sure can fail though.

 

 

 

???????????

 

May just be a language barrier, down south we say alternator overcharging. Maybe because before the ECU etc. there was a

regulator in the alternator.

[danno 128]

You could have an intermittent failure in your regulator or the connections to it. It probably produced a very high voltage, and burned up whatever was on at the time. This would include the lights mentioned, and maybe the gauges. The things that were off when the spike hit, like the radio, are still ok. The coil and operation of the motor will be fine at a higher voltage for a long time, so that is why you did not notice it.

 

I would check all ground connections, including the one from the motor to the firewall. Unless you find out what it is, it could happen again?

[Zipppo 11]

Lots of good info here. Yes the car was running and then the lights turned on and poof just that quick everything went. So Possible alternator, voltage regulator, fuses or fuses and or headlight switch and check grounds. Anything elese? I hope the printed circit borad did not fry. The speedo, temp and oil pressure gauge work just no gas gauge.

[Raven R code 281]

From my new experience......check the circuit board . Spent a few weekends searching g for my problem and it was the circuit board.

[danno 128]

If your temp and oil gauges work, then the problem with the gas gauge has nothing to do with the bigger problem you have. Maybe you are out of gas? :-)

 

I would guess the larger problem is not the headlight switch or fuses. There is just nothing about any failure in them that could cause the bulbs to burn up. The only thing that could do this is a high voltage. That is the charging system, you probably have a weak connection somewhere.

[Zipppo 11]

No the tank is full of fuel. All gauges except fuel work. I checked the ground at the tank. Probably the sender . Odd how it happened at the same time.

 

I spoke with a friend of mine that is more electrically inclined then I am. He said start the car and then disconnect the negative side to battery if it dies most likely alternator and or. He said then reconnect negative cable and restart. Pull the connector to voltage regulator and take a paperclip run it from 1st to 3rd slot and the alternator should change pitch if it does then he said it is the voltage regulator if not then alternator. He also said to check grounds fuses etc... So I plan next week tues on day off to check it out. If all else fails I guess change both alt and regulator and replace all old fuses. Pull dash and look at circut board if wasted replace it and regulator behind dash along with headlight switch and clean all grounds. look and see if and damage to wires from headlight sockets back. Chnage headlight bulbs and see what happens. If that does not solve it then take it to an electrical specialty auto garage and get gouged. Ah old cars love them and hate them.

[det0326 179]

No the tank is full of fuel. All gauges except fuel work. I checked the ground at the tank. Probably the sender . Odd how it happened at the same time.

 

I spoke with a friend of mine that is more electrically inclined then I am. He said start the car and then disconnect the negative side to battery if it dies most likely alternator and or. He said then reconnect negative cable and restart. Pull the connector to voltage regulator and take a paperclip run it from 1st to 3rd slot and the alternator should change pitch if it does then he said it is the voltage regulator if not then alternator. He also said to check grounds fuses etc... So I plan next week tues on day off to check it out. If all else fails I guess change both alt and regulator and replace all old fuses. Pull dash and look at circut board if wasted replace it and regulator behind dash along with headlight switch and clean all grounds. look and see if and damage to wires from headlight sockets back. Chnage headlight bulbs and see what happens. If that does not solve it then take it to an electrical specialty auto garage and get gouged. Ah old cars love them and hate them.

 

I don't know if I would remove the battery cable while car is running.

I have done this in a quick and dirty test but it is not recommended.

This can also cause an over voltage/current condition that is why everyone is telling you to check grounds because this could be just like removing a cable if it is not getting a good connection. I would not jump any reg. terminals with a paper clip either. You can check the status of your alternator/reg. by simply checking the voltage at the battery terminal with engine running it should measure about 13.8 volts if it is working normally. If alt. is not charging it will measure around 12 volt or maybe a little less depending on the state of your battery. If it is charging more than it should this same test would indicate that as well the voltage measurement would be higher, to burn out headlight bulbs I would think it would have to be well over 14 volts or so. I would check the voltage as stated above with engine running if normal I would check/clean battery cables and any grounding straps between engine and chassis then replace headlights and monitor the voltage at the battery terminals while turning the headlights on and off. These conditions are sometimes hard to find but when you do find the problem it is usually something simple.

Dave

Edited May 21, 2014 by det0326

[Midlife 814]

I don't know if I would remove the battery cable while car is running.

I have done this in a quick and dirty test but it is not recommended.

This can also cause an over voltage/current condition that is why everyone is telling you to check grounds because this could be just like removing a cable if it is not getting a good connection. I would not jump any reg. terminals with a paper clip either. You can check the status of your alternator/reg. by simply checking the voltage at the battery terminal with engine running it should measure about 13.8 volts if it is working normally. If alt. is not charging it will measure around 12 volt or maybe a little less depending on the state of your battery. If it is charging more than it should this same test would indicate that as well the voltage measurement would be higher, to burn out headlight bulbs I would think it would have to be well over 14 volts or so. I would check the voltage as stated above with engine running if normal I would check/clean battery cables and any grounding straps between engine and chassis then replace headlights and monitor the voltage at the battery terminals while turning the headlights on and off. These conditions are sometimes hard to find but when you do find the problem it is usually something simple.

Dave

+1. You can blow the diodes out of the alternator by disconnecting the battery cable.

[Zipppo 11]

Okay I will go the route you recommend. thnk you. Now say the alternator reads good would it be prudent after checking grounds and cleaning cables to replace the voltage regulator as a precaution? They are pretty inexpensive. Lastly how about the dash lights and the blinker lights in the cluster could it be as simple as a blown fuse or could say overcharging alternator pop all the bulbs and or circut board?

[det0326 179]

Okay I will go the route you recommend. thnk you. Now say the alternator reads good would it be prudent after checking grounds and cleaning cables to replace the voltage regulator as a precaution? They are pretty inexpensive. Lastly how about the dash lights and the blinker lights in the cluster could it be as simple as a blown fuse or could say overcharging alternator pop all the bulbs and or circut board?

 

 

If the alternator does test normal and you find no other reason why it burned out your headlights then yes I believe I would change the

voltage regulator it could be an intermitting problem with the voltage reg.

Check fuse for instrument lights first (assuming none of them work) and if it is good I would check bulbs.

I know some of the instrument lights can be a pain to get to with the dash pad in place but I would at least try to get to one that is easiest and see if it is burned out as well. If it is then it could have been caused by the same problem your headlights burned out.

Dave

[Zipppo 11]

So I was able to swing by after work to my garage that I keep my cars in. I started the 70 Mustang and used a voltmeter. I tested the system by negative to negative side of battery cable and positive side to positive battery cable with engine at idle. Voltmeter read 14.50 to 14.51. I moved to the battery posts and same readings. So after speaking with a friend that is good with electrical he said start with the voltage regualtor fiest. Most likely that will do the trick. He also said check the headlight switch which i will do tomorrow on my way home from work. If questionable I will change that as well. Then the running light bulbs head lights. I also will check the small fuse in the fuse block to see if that popped. if it did I will change that aand hopefully that will restore the dash lights. If all of that goes well. I will check the fuel gauge as well. I hope I get lucky with this and it resolves. What a pain this electrical stuff is.