Doctor's Pontiac Posted January 30, 2023 Share Posted January 30, 2023 (edited) I've owned this Pontiac 2 door sedan, 6 volt stock, for more than 12 years but I've never tried to fix the non-working dome light until now. I decided to disassemble to check and found there was no light bulb. I thought it would be an easy fix and installed a correct bulb #88 with 1 filament and 2 contacts. Well, the light turned on but I could not turned it off. I blamed the switch, which looked very damaged, so I installed a new one but the light still remains on. I suspect the prior owner gave up and just removed the bulb to "turn it off". I removed the assembly and found 3 wires shown in the photo: The hot wire goes to one of the bulb contacts and the wire from the door switches (both get connected together) goes to the other bulb contact. There was a 3rd wire attached to the light switch when I removed it but that seems some modification done by prior owner as it is not shown in the wiring diagram and I could not track it to any particular site. So I got the wiring diagram from my shop manual and connected everything as shown on the diagram (and left the 3rd wire loose). From the door switch wire I made a connection to one of the bulb contacts and spliced an other wire going to the light switch. The entire assembly is grounded to the body when touching the roof (see tabs in photo). Everything works fine when I test it with the dome light assembly hanging from the ceiling but as soon as it touches the metal on the body the light remains on all the time regardless of light switch position. The circuit is effectively grounded all the time and I find no way to interrupt it. The light switch is supposed to connect/disconnect the ground but it does not happen. I verified the connections multiple times. The assembly shown before making all the connections. What am I missing in my wiring connection? Thank you for any comments. Manuel Edited January 30, 2023 by Doctor's Pontiac Typos (see edit history) Link to comment Share on other sites More sharing options...
joe_padavano Posted January 30, 2023 Share Posted January 30, 2023 If the wire to the door switches is shorted to ground at all times even with the doors closed, that's your problem. Figure out where the wire is pinched or otherwise shorted to ground, or run a new one. 1 Link to comment Share on other sites More sharing options...
F&J Posted January 30, 2023 Share Posted January 30, 2023 29 minutes ago, Doctor's Pontiac said: Everything works fine when I test it with the dome light assembly hanging from the ceiling but as soon as it touches the metal on the body the light remains on all the time regardless of light switch position. Going by what you said above... I would bet you used the wrong type bulb. If your present bulb gets another ground through the brass base of the bulb, then it is wrong bulb. Your present bulb shows two filaments where a proper dome light bulb has just one. A proper dome light bulb has an isolated brass base so it won't be a ground for a filament. Also, the glass part of a dome light bulb looks different, not as rounded, (and it's a dual contact, but only one filament). 3 Link to comment Share on other sites More sharing options...
Frank DuVal Posted January 30, 2023 Share Posted January 30, 2023 (edited) If you look into the socket with the bulb out, do you see one or two brass contacts? The socket of the lamp looks like it is firmly attached to the base, no insulator between them, so I suspect, as F&J says, you need a dual contact single filament 6 volt lamp. A #82 is an example. Of course, you need to see two brass contacts when you look into the socket. I only see one wire coming out of the socket in your picture. The two brass contacts, one should go to hot, the other contact to the dome light switch and door switches. Now, if the socket only has one contact, and that one is right in the center of the base, no other hole in the base, then the problem is the socket needs to be insulated from the base. And a single contact bulb would be used. Edited January 30, 2023 by Frank DuVal (see edit history) 4 Link to comment Share on other sites More sharing options...
37_Roadmaster_C Posted January 30, 2023 Share Posted January 30, 2023 (edited) Looking at the picture, you have the wrong bulb for sure. What I see in the picture is a dual filament bulb. This bulb grounds both filaments to the brass base. What you want is a single filament bulb with an isolated filament. I am not sure of the bulb number, but someone will chime in with the answer. A little quick research shows the proper bulb to be a number 82. Edited January 30, 2023 by 37_Roadmaster_C (see edit history) 2 Link to comment Share on other sites More sharing options...
Buick35 Posted January 30, 2023 Share Posted January 30, 2023 I know I've mentioned this before but on my 35 Buick my dome light goes out if I open the passenger side front door.I've given up on it for now. At least our cars don't have Lucas wiring like my MGB. 1 Link to comment Share on other sites More sharing options...
Oldtech Posted January 30, 2023 Share Posted January 30, 2023 You need, as 37 says, the correct bulb. The 12 volt version is a 1004 but I don't know the 6 volt number. Link to comment Share on other sites More sharing options...
Frank DuVal Posted January 30, 2023 Share Posted January 30, 2023 I said, #82. Robin also said it after my post. 2 Link to comment Share on other sites More sharing options...
37_Roadmaster_C Posted January 30, 2023 Share Posted January 30, 2023 5 hours ago, Frank DuVal said: I said, #82. Robin also said it after my post. Sorry @Frank DuVal, I missed the bulb number in your post. Link to comment Share on other sites More sharing options...
Bloo Posted January 30, 2023 Share Posted January 30, 2023 I'm just amazed all you guys can remember that bulb number. @Doctor's Pontiac, as has been already mentioned the filament of the correct bulb runs between the two socket tips. You should have a hot wire up there. That goes to one of the tips. Ground the other tip to turn the light on. You can ground it with a door switch or with that switch in the dome light. Both hook to the second tip and either can turn the light on. The socket ground (shell) is unused except to hold the bulb in. Link to comment Share on other sites More sharing options...
Doctor's Pontiac Posted January 31, 2023 Author Share Posted January 31, 2023 1 hour ago, Bloo said: I'm just amazed all you guys can remember that bulb number. @Doctor's Pontiac, as has been already mentioned the filament of the correct bulb runs between the two socket tips. You should have a hot wire up there. That goes to one of the tips. Ground the other tip to turn the light on. You can ground it with a door switch or with that switch in the dome light. Both hook to the second tip and either can turn the light on. The socket ground (shell) is unused except to hold the bulb in. Thank you all. I am also amazed how many of you can spot tiny details that can get unnoticed easily (like the filaments in the photo above). I checked the bulb and indeed I used the wrong one. The correct one is the #88 with 2 contacts tips for the socket and a single filament. I had my bulbs in the same small package and accidentally I installed one with 2 filaments although I intended to use the single filament one. So far this is what I have accomplished: both door switches work well and turn the light on and off correctly but only while the assembly is not touching the body. As soon as the assembly contacts the top (metal to metal) the light turns on and can not be turned off with the switch. This happens with the correct bulb. Will try to figure out where is grounded, may be a short with old dry wires running through the car roof? 1 Link to comment Share on other sites More sharing options...
pfloro Posted January 31, 2023 Share Posted January 31, 2023 (edited) I don't think that one of the wires running to the door switches is the problem. If that were the case, the lamp would glow continuously when the housing is dangling by the wires. As you said, it functions properly when dangling... I suspect that the problem is with the slide switch. In the "off" position (and perhaps in the "on" position too), it may be grounding to the case of the lamp housing. Everything is OK until you ground the case to the body's roof structure. Take the switch "out of the equation" and test again... Studying the wiring diagram make a light go on in my head.. ! Paul Edited January 31, 2023 by pfloro (see edit history) 1 Link to comment Share on other sites More sharing options...
Bloo Posted January 31, 2023 Share Posted January 31, 2023 I agree. The bulb contact that the door switches are connected to is grounded to the housing somehow and it shouldn't be. Well, it shouldn't be except when the switch connects it. Link to comment Share on other sites More sharing options...
37_Roadmaster_C Posted January 31, 2023 Share Posted January 31, 2023 Bulb number 88 is NOT the correct bulb. It MUST be a number 82 or equivalent. Link to comment Share on other sites More sharing options...
Frank DuVal Posted January 31, 2023 Share Posted January 31, 2023 #88 is a double contact Ba15d base, so it will work properly. It is higher candlepower than a #82. I suggested the smaller bulb, as I did not want to melt the lense giving bad advice. If the owners or shop manual says 88, that is great, at least you can see when you open a door at night! 17 hours ago, Bloo said: I'm just amazed all you guys can remember that bulb number. Google is the answer. Also I worked in electronics and had to look up many miniature lamps in repair work, used to use paper catalogs from Sylvania and Chicago Miniature Lamps. The Newark and Allied catalogs also had miniature lamp pages. If the light comes on when the base is touched to ground then either the internal switch is ON or a wire to that switch is touching the base. Are the wires in the socket insulated now? I see bare wire in an earlier picture. Needs to be two wires, one for each brass terminal and they need to be insulated. 1 Link to comment Share on other sites More sharing options...
Doctor's Pontiac Posted January 31, 2023 Author Share Posted January 31, 2023 9 hours ago, 37_Roadmaster_C said: Bulb number 88 is NOT the correct bulb. It MUST be a number 82 or equivalent. I got the #88 based on the Shop Manual. I am sure others will work but probably have different candlepower. The # 82 in the Manual is listed for the 1951-1954 Catalina and Convertible courtesy lamp (see below). The # 82 has 6 C.P and the #88 has 15 C.P., both single filament, dual contact. 4 hours ago, Frank DuVal said: If the light comes on when the base is touched to ground then either the internal switch is ON or a wire to that switch is touching the base. Are the wires in the socket insulated now? I see bare wire in an earlier picture. Needs to be two wires, one for each brass terminal and they need to be insulated. It seems several of you think the switch and/or connections are not insulated properly. Tomorrow will work on this issue with a friend who is very able and has helped me many times. Got to fix this tomorrow because have to travel the day after for a while away from this car!! Fingers crossed. Thank you 1 Link to comment Share on other sites More sharing options...
37_Roadmaster_C Posted February 1, 2023 Share Posted February 1, 2023 (edited) @Doctor's Pontiac, I stand corrected. You are absolutely, 100% correct, as shown in your manual page. My number came from someone I felt was in tune with your 50 Pontiac. He was obviously wrong!!! I will eat my CROW head first do the feathers do not get caught in my throat 😇. Ok, I now need to eat another crow. I was going to go look up the difference between the two bulbs before I went back and read ALL of your post. You answered my question with your candle power specifications... I will now go off and digest my crow dinner. Edited February 1, 2023 by 37_Roadmaster_C more info (see edit history) Link to comment Share on other sites More sharing options...
Doctor's Pontiac Posted February 1, 2023 Author Share Posted February 1, 2023 Problem solved thanks to all your tips, thank you! In summary, the main issue was the wrong bulb. Evidently using a 2 filament bulb provided current all the time regardless of position of the dome light switch. These 3 photos show how I finally installed and is working correctly. Both door switches and the dome light switch operate independently and correctly. First of all had to check the socket wires that were suspected of grounding the circuit all the time. The first photo shows NO continuity between either one of the 2 socket wires with the case which confirmed there were no shorts in the socket. Then we (my friend and myself) made the connections from the 2 wires as shown in next photo: Notice an extra white wire coming from the metal tab on the roof to the dome switch ground connector. This is needed for this aftermarket switch in order to complete the ground circuit. With the above setting everything works correctly now ! Very happy with results I then cleaned and polished the dome light cover and is all done! Thanks again to all!!👍 Manuel Quote 7 Link to comment Share on other sites More sharing options...
37_Roadmaster_C Posted February 1, 2023 Share Posted February 1, 2023 Glad you got it repaired. Looks great!!! Link to comment Share on other sites More sharing options...
Frank DuVal Posted February 3, 2023 Share Posted February 3, 2023 Yay!👍 Link to comment Share on other sites More sharing options...
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