Brake light and turn signal drivers side out only.

[USN_Green_Addict]

I have a 1966 M35A2. Due to my rear drivers side blinker/stop and marker not working I decided it was a good time to replace the rear wire harness, and driver rear bulb housing. Even after replacing both I only have a extremely dim turn signal , no stop or marker. What else could it be?

I did try to tighten up the back of the light selector switch. The turn signal works on both fronts and passenger rear. I did just use a flap wheel to make sure the driver rear is grounded.

 

[Mullaney]

I have a 1966 M35A2. Due to my rear drivers side blinker/stop and marker not working I decided it was a good time to replace the rear wire harness, and driver rear bulb housing. Even after replacing both I only have a extremely dim turn signal , no stop or marker. What else could it be?

I did try to tighten up the back of the light selector switch. The turn signal works on both fronts and passenger rear. I did just use a flap wheel to make sure the driver rear is grounded.

.
You might try looking at the ground for the lights.
Clip an alligator clip to the negative post on on your battery at one end of the wire - and the other end to the "light bucket" and see if anything changes.

 

[msgjd]

1: Are the inside of the bulb sockets rusty, dirty, or have the typical white-powder corrosion? If not, I would take a meter measurement between a good ground source and each wire end-tip inside each bulb socket to see if you have the full 24V+ there (and also check it at the connectors coming off your harness) .. An analog (needle-type) meter is best when checking flasher voltage ..

2: It never hurts to run a ground wire from the battery ground post directly to the object in question, such as the light can, as an additional step in the process of elimination

3: If the basic checks come up empty, there is always the fluid level check to do

 

[USN_Green_Addict]

1: Are the inside of the bulb sockets rusty, dirty, or have the typical white-powder corrosion? If not, I would take a meter measurement between a good ground source and each wire end-tip inside each bulb socket to see if you have the full 24V+ there (and also check it at the connectors coming off your harness) .. An analog (needle-type) meter is best when checking flasher voltage ..

2: It never hurts to run a ground wire from the battery ground post directly to the object in question, such as the light can, as an additional step in the process of elimination

3: If the basic checks come up empty, there is always the fluid level check to do


View attachment 925534

Would a bad flasher unit affect the brightness or would it stop completely?

 

[msgjd]

Would a bad flasher unit affect the brightness or would it stop completely?

1: any bad flasher units that i had don't flash at all, but others may have had different experiences with them

2: although you have a new housing (can) , do a continuity check between your ground wire connector tip on the can pigtail and the metal holding the sockets .. I have seen new parts have problems before, very rare, but it happens .. Being you have a 1966 truck, I was thinking it may still have had the original aluminum light cans, which are prone to internal corrosion

3: put all your bulbs in and touch a hot wire to each of the pigtails (except the ground one of course)

4: have you checked for proper voltage at the wiring harness connectors yet? (with light can unhooked)

5: the symptom screams to be a grounding issue, but you seem to have that covered .. you just might want to make double-sure the ground wire on your "new" harness is getting good continuity at its connections ... Mullaney's suggestion is right-on as well

 

[USN_Green_Addict]

1: any bad flasher units that i had don't flash at all, but others may have had different experiences with them

2: although you have a new housing (can) , do a continuity check between your ground wire connector tip on the can pigtail and the metal holding the sockets .. I have seen new parts have problems before, very rare, but it happens .. Being you have a 1966 truck, I was thinking it may still have had the original aluminum light cans, which are prone to internal corrosion

3: put all your bulbs in and touch a hot wire to each of the pigtails (except the ground one of course)

4: have you checked for proper voltage at the wiring harness connectors yet? (with light can unhooked)

5: the symptom screams to be a grounding issue, but you seem to have that covered .. you just might want to make double-sure the ground wire on your "new" harness is getting good continuity at itsand connections ... Mullaney's suggestion is right-on as well

Ok I tried using a wire directly to the battery negative and touched the end to the light socket. Absolutely no change. I'm looking fory multimeter to get voltage.

I also just noticed it is affecting the driver front as well as rear.

 

[Mullaney]

Ok I tried using a wire directly to the battery negative and touched the end to the light socket. Absolutely no change. I'm looking fory multimeter to get voltage.

I also just noticed it is affecting the driver front as well as rear.

.
Hate to say it, but that means you definitely have a grounding issue...

 

[USN_Green_Addict]

.
Hate to say it, but that means you definitely have a grounding issue...

I'm a amateur mechanic. Can you please explain? The light didn't get brighter after I tried a true battery ground. I thought that would be a supply issue.

 

[USN_Green_Addict]

 

[USN_Green_Addict]

Multimeter reads 23.5 volts

 

[Valley Rock]

Sounds like you have a short on that side, so it is a supply problem if you asked the bulb .

Which is dimmer the front or the rear ?

Whichever is dimmer your short is on that end .

You can also feel for some heat in the wire, whichever one is warmer is going to be where your problem is, if you can't feel it with your hands ( probably not because it's intermittent) possibly try a temp gun, or just look for a place where wires are touching metal .

Personally I'd be suspicious of the light housings, start disconnecting until the problem goes away it's process of elimination

 

[USN_Green_Addict]

Sounds like you have a short on that side, so it is a supply problem if you asked the bulb .

Which is dimmer the front or the rear ?

Whichever is dimmer your short is on that end .

You can also feel for some heat in the wire, whichever one is warmer is going to be where your problem is, if you can't feel it with your hands ( probably not because it's intermittent) possibly try a temp gun, or just look for a place where wires are touching metal .

Personally I'd be suspicious of the light housings, start disconnecting until the problem goes away it's process of elimination

They both look about the same. I'm just so confused with it having 23v it's probably because both batteries are down at nearly 11 volts.