1948 Roadmaster model 71 Electral Problems

[rdmst71]

The tail lights,stop lights, Trunk light, dome light, front & rear courtesy lamps have all stop working. The first to go were the tail lights, which started to work again for a short time and then one by one the other lights failed. All bulbs are good and the head lights, parking lights, instrument panel and all other electral items are working. Today the starter would not turn over but the battery is fully charged. Per my shop manual, the tail and stop lights are not protected by a fuse and I can not locate any loose connections. Fuse's for the other lamps are located some where behind the dash panel but the shop manual does not give exact locations as to what fuse's are where.

Any ideas as to what may be the cause of this and is there any way to try and slove this other than trying to use the wireing diagrams in the shop manual.

:confused:

[Guest ewing]

sounds like you could have a regulator problem.

I am just learning about the regulator and the settings wrt to the generator. I understand that regulators rarely fail,. However if they are set wrong, with a voltage adjustment that is outside the 'normal ramge' that it can cause lights and any other voltage sensitive things....to fail.

stop running the car and check the regulator, or replace it.

I am not an expert, so others will likely add to this opinion... but that is where I'd start!

[trp3141592]

Hi,

Clean the contacting surfaces of the strap connecting the frame and the body. A high resistance contact here can isolate the body and cause seemingly inexplicable problems.

--Tom

[rdmst71]

Hi Tom,

Looked under the car ( front to rear ) and I can not seem to locate a strap connecting the frame and the body. Should there be some type of ground strap connecting the frame and the body? If this strap is missing where should it have been attached ?

Jim

[jackofalltrades70]

I believe it should be somewhere on the lower firewall on the drivers side? Matt

[trp3141592]

Hi,

I have located this strap--it's like a woven battery grounding cable with a flat fitting on both ends--on two of my cars at the bottom of the firewall on the passenger side under the hood where the passenger floor meets the frame. I don't know for a fact where it is in yours. If it doesn't exist you can add one by installing one end of a auto-store woven strap under a body bolt and the other to a convenient location on the frame. Clean the surfaces to bare metal before you tighten down the strap.

I became aware of this possible problem when a '67 GTO that I had was doing bizarre and unpredictable electrical things. A seasoned mechanic listened to my tale of woe and immediately told me the answer. Cost to repair was zero dollars and ten minutes of relatively minor effort.

--Tom

[rdmst71]

Thanks for the information on the ground cable and the regulator.

After taking a few days away from car repairs, this past weekend I installed a ground cable between the frame and the body, where it was supposed to have been and my lighting problems were sloved. I was not able to locate the original ground cable but since this problem just started a short time ago it must be on the car somewhere and either the connections are corroded or the cable has broken.

Jim:rolleyes:

[trp3141592]

Hi Jim,

So glad that the problem has been solved!!

--Tom

[Guest Straight eight]

Thanks for the information on the ground cable and the regulator.

After taking a few days away from car repairs, this past weekend I installed a ground cable between the frame and the body, where it was supposed to have been and my lighting problems were sloved. I was not able to locate the original ground cable but since this problem just started a short time ago it must be on the car somewhere and either the connections are corroded or the cable has broken.

Jim:rolleyes:

I think the ground you are looking for is the outer covering over the heat gauge tube to the block. This cable covers the copper tube that picks up the engine temperature and sends it to the dash while the outside is grounded to the firewall.

Many times left loose when engine is worked on. It is on the passenger side just above the engine block, and coming from the engine block to the firewall.

[Ben Bruce aka First Born]

As per Straight eights post, if your spark plug cover is still in place, it will be hidden underneath it. It comes out of the head.

Ben

[rdmst71]

I did find this short ground cable which covers one end of a tube connected to the cylinder head and is attached to the fire wall at the other end. This ground connection is for the temperture gauge which was still working.

I disconnected both ends and cleaned the connection points to be sure of a good connection. It appears that the missing ground between the frame and the body was the cause of my problems.

Thanks for the response, I do welcome all of the input. I will check out anything that may have been a part of this problem

Jim