No Back up lights

First, you really need to determine if there is voltage coming off, or even going to, the back up switch. Then find out if it is making it to the wiring harness at the tail light housings. Get a test light, or voltmeter and find out.

Sometimes the lamp sockets, while appearing solidly mounted in the metal strap that runs the full width on the back of the housing, develop a corrosion that prevents the grounding portion of the circuit from getting to the lamp. This is an internal corrosion and may not be readily visible. Take an ohm meter and check for continuity between the strap and the socket.

If not there, try twisting the socket to break free from the corrosion. Second technique would be to use a sharp awl or center punch and hammer some indentations in the socket ring, where it is crimped into the strap. Use a proper size socket to provide a back-up so you don't damage the plastic housing.

Try these tricks before spending money on a switch that you may not even need.

Larry

...Test the Back-Up lights by 'jumpering' the two wires that go to the switch. REMEMBER!!! some Panteras must have the ignition key in the 'Run' position for different lighting to work. I also believe (in RARE cases) that You may need to have the 'Headlight' switch ON, before the Back-Up lights will work. Check it out! And good-Luck! Let us know what you find out...

Marlin,
I did read some old posts on the "other" forum. I have tried it with the ignition in the run position and with the headlights on. No luck. I will try checking the wires with my test light next weekend. By the way if it turns out to be the back up switch , a good source , and price in what range ?
Thanks,
Jeff

Graham has factory upgrade switches for around $50. It is a sealed switch as opposed to the rather archaic switch installed from the factory. His number is 714.283.3926.

I bought this from him, great quality switch not like the stock POS. Price has gone up significantly since it was first offered though.

Today, I checked for power at the inside of the switch. The test light indicated that I have power inside the switch with the plunger depressed. I next checked for power inside the back up light socket and found no power. The test light should come on with the test light needle against the contact inside the socket with the plunger depressed right ?

I do not think I have a corrosion issue as these are NOS units. All contacts are bright and shiny. Turn indicators, brake lights and tail lights are working fine on both sides.
Any new ideas ?

I thought I heard or read somewhere that your headlights had to be on for the reverse lights to come on. I've never checked and my memory is not that good. has anyone heard of this before or do I need to get more sleep?

John

quote:

The test light should come on with the test light needle against the contact inside the socket with the plunger depressed right ?

Yes.

Test again and make sure igniton is on. Then test again and make sure lights are on.

Corrosion issue is between the ground contact of the socket to the metal strap which leads to the mounting stud where ground is landed.

Larry

I heard about some P cars needing the lights on. The ignition is in the run pos. and tried headlights on. Nothing. Is it possible that the Altissmo lights are wired differently than my original Carellos ?

...I'am getting the feeling that the Ground is bad! Did you ground your test light to the chassis? OR the ground 'IN' the socket?? If you grounded in the socket; then try it to the chassis. The back-up light 'Ground wire' grounds at two different studs at the rear tail bulkhesd, at least on the '74, they do...

...other than 'that' if Both sides of your pantera have working lights, then it is NOT a fuse. It would have to be a 'Broken Wire' somewhere in the curcuit. I'll check My schematics and get back to you...

...did you ever try jumping/shorting the Back-Up Switch on the ZF?? Was there 12 Volts DC Found there?...

Guys,
Thanks for your help. I grounded the test light on a bolt on the AC fan shroud. Am I correct that the test light would not work without a proper ground ? If I did not have a proper ground at the studs is it possible for the other lights to work ?

quote:

Am I correct that the test light would not work without a proper ground ? If I did not have a proper ground at the studs is it possible for the other lights to work ?

Test light needs ground.

GRP 4 lights only ground at the one mounting stud. If you have some lights working then they have a ground and thus you will have all lights grounded, as the ground gets to all sockets through the flat metal piece all the sockets mount to. And YES, as I wrote very early on, a fine looking socket could have corrosion issues blocking the ground - but this is highly unlikely for only BOTH backups to have that problem.

Carello and Altissimo light plugs are wired the same, whether stock or GRP 4. Unplug the stock, plug in the GRP 4 and everything should be fine.

Have you taken a stock light and remounted it to see if IT had a backup light?

Remember, just plugging it in will not be enough, you will have to mount it and make sure it has a ground. I think this is the next step you should take.

Have you taken a KNOWN good bulb and swapped it for a back up bulb? Your back up and yellow signal bulbs are the same.

Stay with it and you'll find the problem. You won't need a three foot breaker bar, get your hands all greasy or have to remove the engine. Electrical problems are not hard, just time consuming.

Do you have, or can you borrow, a multimeter/voltmeter? Or a continuity tester?

If you want talk this out, I'm home all weekend. California, 559-281-3497

Larry

Larry,

The buckets are mounted. I have tried new bulbs and nothing. What is frustrating is that all other lights work fine. I guess the next step is to try the old buckets and see if they work. I am very electrically challenged and would not know what or how to use a meter. What will this tell me that a test light does not ?

Just one more thought. Could I have a bad connection at the fuse box? Which fuse holder on a 72 Pre L and color wire ?

quote:

Just one more thought. Could I have a bad connection at the fuse box? Which fuse holder on a 72 Pre L and color wire ?

Swap in an old bucket. Then let's see what we have to deal with.

You can get a cheap meter at Harbor Freight and I'll talk you through the testing methods. Continuity or ohm meter would tell if we had a corrosion issue or open wire.

Nothing but time and measured steps of troubleshooting.

Larry

...OK here's the last word I have to help you! I studied the wire schematics that work exact with My '74. 1) A (aprox.) 10 gage RED wire comes off the Positive terminal of the Battery, goes through the front bulkhead to the AMP gauge. 2) From the AMP guage comes a BLACK wire that splits off into 4 PINK wires. Don't get confused!! The only PINK wire You have to be concerned with, is the One that terminates at the Ignition Switch. Yes! This is supplying The Ignition Switch with 12 Volts DC. 3) From the Ignition Switch, when at the 'RUN' position, comes a RED wire that supplys power to FUSE #11 at THAT point there is a 'JUMPER' (brass bar) that also SHARES this 12 Volts with FUSE #12, this IS the fuse Your concerned with! 4) Off the other end of FUSE #12, comes a GREEN wire that travels straight back through the FIREWALL on the Passenger side, and near the wheelwell; goes through a Plastic 'Multi Contact' PLUG, (THIS may be A source of Your Problem. As corrosion here is inevitable!). That GREEN wire, after the Plug Connection, Continues GREEN all the way to the ZF Transaxle To the 'Back-Up Light' SWITCH!! 5) There should be 12 Volts here when the Key is 'ON'. 6) From that same switch, comes a WHITE Wire, to the 'HOT' contact of BOTH B.U. Light Sockets. (The wire was split on the drivers side). 7) From BOTH sockets goes a BLACK wire directly to ground at the STUD in the center of the Rear Tail Bulkhead. In fact ALL the BLACK wires in the 'Rear Wire Bundle' go to ground. That completes the curcuit; PROVIDED Your Battery is Grounded to the chassis in the first place!!! I asked you if you 'Shorted' the Back-Up switch to Test it as being Good! I have not heard an answer. This gives You a couple more things to check out, and is all the help I have for you. Check for 12 Volts at that 'multi contact' PLUG, and AT the BACK-UP SWITCH. Make certain that the GROUNDS 'IN' Light BUCKETS are GROUNDED, as Larry F. pointed out. Lets get these Lights fixed!! And then get back to us!...

Wow Marlin !, Thanks for your research and detailed wiring analysis. I am not sure if this answers your question, but please bare with the electrically/mechanically challenged. I used my test light on the switch at the outside terminal and after removing the cover and cleaning up the inside contacts. I did have power on both inside contacts with the plunger depressed. Are you asking me to try the contact with the white wire outside terminal ?

I will also confirm my center ground. I was under the impression that all rear lights grounded at the two studs on the housing.

Last I will reinstall one of my old light assemblies and see if I had back up lights. I have been told that some assemblies had different contact pin placement such as Euros with the lower amber lens.

Thanks again, to all for your suggestions.
Jeff