Alfa Romeo Forums banner

1 - 12 of 12 Posts

·
Registered
Joined
·
111 Posts
Discussion Starter #1
On My 66 Sprint GTV:

I have a small issue where out of the two red rear tail lamps, one is markedly brighter than the other.

I looked at this a while ago, it was made worse when I used LED bulbs.

The loom is unequal length, i.e the wires to one tail lamp are longer than the other.

I think I voltage tested both a long time ago.

I also cleaned up the earthing points and connectors.

Is this a know issue? any Hints??
 

·
Registered
Joined
·
1,015 Posts
Check the quality of the earth.
Check the current not just the voltage.
Put two new lamps in (luminous flux can vary between lamp manufacturers and batches)
Take both lenses off and check....
Back Reflector is clean an dirt free, of equal condition.
Hold both lenses upto a bright overcast sky side by side, check equally clean or for variation in opacity.
 

·
Registered
Joined
·
1,531 Posts
The Left side typically gets dull due to the exhaust. I've got NOS lenses if you're interested to replace them.
 

·
Registered
Joined
·
180 Posts
Sounds obvious, but are you sure one side isn't connected to the brake light and the other side to a park light?
 

·
Registered
Joined
·
2,310 Posts
Pancho's right. The left side gets covered in soot from the exhaust. How about taking off both lenses and comparing the bulbs just by themselves. Or swapping lenses (keeping them in place with some tape) and seeing if the dimming switches sides.
 

·
Premium Member
Joined
·
21,714 Posts
I took mine all apart, cleaned wires, connections, grounds, inside of housing, left side lens was sooted, as described above, but inside chrome was also more decayed than right side. Painted inside surfaces with a reflective chromy silver, reassembled, much better for the cost of a spray can and a couple hours' work.

Andrew
 

·
Registered
Joined
·
111 Posts
Discussion Starter #7
Thanks for all of the tips guys. I will do some more checks when I'm next with the car.

From memory, it is the exhaust side that is dim,and the seal is a bit iffy on that side.
 

·
Registered
Joined
·
426 Posts
I had the same problem which I solved like Andrew by cleaning all electrical contacts, but then made reflectors from 0.007 inch thick stainless steel shim stock (can be cut with regular scissors).

I polished the stainless steel using Simichrome Metal Polish so that I could see my reflection in the polished surface, then installed the shim stock in the lamp housings so that the metal bowed in such a way that the polished surface does a very good job of reflecting the light from the bulbs outward towards someone behind the car. I recently had to change a light bulb and found that after four years in service the polished metal surface still had a mirror like finish.

I bought a 50 foot long by 6 inches wide roll of the shim stock (316 stainless or "A4") from McMaster-Carr here in the U.S. for circa $20.00. For me this it was cheaper than a can of the "chrome like" paint. (I used the shim stock primarily out of concern for the durability of the paint) I ended up making reflectors for all of my lamp assemblies on my GTV.

Bob
 

·
Registered
Joined
·
111 Posts
Discussion Starter #9
So, had a very short play with this last night.

Voltage both the same.

Went to measure resistance but clumsily broke the fuse inside my multimeter!

What I did find was that the LED bulbs I put in a year or so ago may be suspect.

One is brighter than the other when you swap sides. I tries with normal bulbs and all ok.

Have ordered some new LED ones, I want them brighter to protect my rear end :)

I also cleaned and checked the lhs lens, it seemed OK but it did have a small crack where dust can get in.

Also, when it comes to reflectors, I have none present that I can see, unless the central divider section should be chromed? It is a dull black, and seems to be there to divide the tail lamps from the indicators.

Remember these are the early light lenses on my 66 GTV....
 

·
Super Moderator
Joined
·
10,634 Posts
Voltage both the same. Went to measure resistance but clumsily broke the fuse inside my multimeter!
How are you measuring the voltage? Remember, your voltmeter has high impedance, so no matter how much resistance there might be in the circuit, you are going to measure 12V on the hot side of the socket with the bulb out. The most pertinent measure is the voltage between the hot side of the bulb and ground with the bulb installed and lit (that is, with current running through the circuit).

What I did find was that the LED bulbs I put in a year or so ago may be suspect. One is brighter than the other when you swap sides. I tries with normal bulbs and all ok.
Well, that sounds like your answer.

when it comes to reflectors, I have none present that I can see, unless the central divider section should be chromed? It is a dull black, and seems to be there to divide the tail lamps from the indicators.
Sorry, that wasn't clear. Are you saying that the entire inside of your lamp housing is black? That wouldn't be good, though it will be less of a problem with LED's than with conventional bulbs: LED's direct their light rearward, while incandescent bulbs shine in all directions so they need a reflector to turn around those pesky photons that were sent forward or sideways.
 

·
Registered
Joined
·
111 Posts
Discussion Starter #11
Answers in bold.....

How are you measuring the voltage? Remember, your voltmeter has high impedance, so no matter how much resistance there might be in the circuit, you are going to measure 12V on the hot side of the socket with the bulb out. The most pertinent measure is the voltage between the hot side of the bulb and ground with the bulb installed and lit (that is, with current running through the circuit).

Yes Measured like this.



Well, that sounds like your answer.



Sorry, that wasn't clear. Are you saying that the entire inside of your lamp housing is black? That wouldn't be good, though it will be less of a problem with LED's than with conventional bulbs: LED's direct the light rearward, while incandescent bulbs shine in all directions so they need a reflector.
The inside is white plastic, but there is a black dividing flap.
 

·
Super Moderator
Joined
·
10,634 Posts
The inside is white plastic, but there is a black dividing flap.
I'm not sure if that's original - there may have been a metallic, vacuum deposited coating over the white plastic. But the white finish is probably good enough, particularly with LED's.
 
1 - 12 of 12 Posts
Top