When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Now comes the electrical problems, first of all I analyzed the complete electrical diagram of the car at length. I found it in PDF, going to the printer to print it in A0 color.
I have already solved a lot of problems, between bad bulbs, oxidized masses or even disconnected connector wire, it was not glorious.
The worst was some kind of yellow paste that was in half of the bulb connectors, it dissolved in contact cleaner but it was long. I only have one problem left to deal with.
I've scoured the forums and videos but nothing quite close. I understood that it is necessary to have a mass everywhere in good condition, I have already tested everything with a multimeter and stripped the necessary.
On this model the bulb connectors always return the ground by a wire, I have not encountered any metal connector in contact on the chassis for the ground.
In fact I already have some basic questions, I didn't particularly know American cars before having this oldsmobile (Jaguar Volvo Peugeot Renault Audi Mercedes yes, but not GM ^^)
1: When the park lights are activated (first position of the light switch on the dashboard): is it normal for the turn signals (left and right front only, those on the side of the headlight unit, those orange) to turn on?
By following the diagram I can clearly see that a 12 volt is sent via the brown wire which lights up all the lights linked to the parklights position, therefore flashing them sideways.
The side marker blue wire then becomes a 0v passing through the second filament of the parklight double filament bulb. (see section A1 of image below)
2: the problem that we see in this video that I filmed is more or less identified:
when the parklights are activated and I activate the turn signals (right or left both have the same fault) then the orange indicator (turn signals) of the side goes out and the park lights its second filament.
When the parklights are not on, the turn signals and side marker work perfectly.
By following the electrical diagram I understand a little what is happening and this is where it lacks logic.
When the park lights are not activated the turn signals and side marker work well because the brown wire is a 0v passing through the second filament of the park lights.
By activating the park lights I then send a 12v on this brown wire. As long as I do not activate the turn switch the blue wire of the indicators is a 0v, hence the fact that they light up when the park lights are on (see question 1)
So when there is flashing + park light, the blue wire sends a 12v, and the brown wire too. (see section A1 of image below)
Obviously the blinkers on the side (orange / side markers) stop because 12v at both terminals.
The flashing filament of the park light does not flash because there is not enough amperage for the bimetallic strip.
I must be missing an element of understanding. In a certain logic when pilot light and indicators are activated there should be a system allowing to cut the 12v of the brown wire to return it to 0v, but I do not see it on the diagram.
I tried to make it as clear as possible but not sure if it is.
hi rez electric diagram delta 88
Last edited by maitrepathelin; January 11th, 2023 at 08:24 AM.
I was trying to follow your write-up and interpret the diagram. I had to read it numerous times to interpret "pilot" lights and "sidelights". I have neither worked on nor owned a 1978 Oldsmobile Delta 88 Diesel 350ci, collectively members may somehow be able to assist & provide some input.
First however, is terminology. It's critical to use the same terminology identified in the wiring diagram:
(1) There are "park" (parking) lamps;
(2) There are "cornering" lamps;
(3) There are "side marker" lamps;
(4) There are "turn signals"; and,
(5) There are "headlamps". Headlights is fine, but stay with the written terminology in the wiring diagram.
NOTE: It may be noteworthy to know if your car is equipped with a "lamp monitor". If you have a lamp monitor, have you reviewed the dimmer switch headlamp wiring in the service manual?
You mentioned the yellow paste in the bulb sockets. Have you cleaned all the bulb sockets? This is just coagulated dielectric grease. If the bulb sockets aren't clean and making good contact, this could contribute to the problem your having.
Sorry for the somewhat wild terms used, I use Google Trad to have a slightly correct syntax. Otherwise
I can write in French but it will be even more incomprehensible ^^
Pilotlights are park lights
Sidelights are the amber turn signals on both sides (front) of the vehicle with a small #194 bulb.
I'm going to go there in a very wild way and place relay cards under the dashboard to cut the 12 volts and put back a 0v when a turn signal is activated, making sure that it goes through the bimetallic relay circuit of the turn signal.
Unless someone would have found the fault before
but I have 10 no/nc din rail relays which are ready to be installed
@Olds64 Thanks for following me on this thread! Yes I cleaned all the connectors well with contact cleaner, it liquefies this grease.
@Vintage Chief I don't have the Twilight Sentinel Control system for automatic headlight regulation, it's only done by the lever on the steering column.
Last edited by maitrepathelin; January 11th, 2023 at 08:29 AM.
First, show us a good picture of the front, rear and sides of your car. You should be able to troubleshoot this with your DVOM by searching for 12 VDC. If you don't have 12 VDC at the lights when they're activated, then you can check at the switch.
First, show us a good picture of the front, rear and sides of your car. You should be able to troubleshoot this with your DVOM by searching for 12 VDC. If you don't have 12 VDC at the lights when they're activated, then you can check at the switch.
^^^THIS. The lights worked from the factory without relays. Adding complexity without understanding the cause of the problem is just adding new potential failure modes.
Ok I put aside for the moment the addition of relays.
But if it's the turnswitch in the steering column that's dead I don't rule out doing it because the customs fees for this kind of parts are terrible.
Looking at the diagram attached to my bay window in the living room, I ask myself an existential question:
in the image below, can you confirm that the bulb circled in purple is indeed the LH Side Marker and the bulb circled in green LH Cornering Lamps?
You are waaaay overthinking this. The side marker bulbs have two wires, the brown wire (which is the park lamp feed) and the blue with white stripe (which is the turn signal feed from the flasher).
With the park lights off, those side marker bulbs ground through the park lamp circuit (the brown wire) which is connected to ground through the park lamp filaments. Activating the turn signal switch applies intermittent 12V to the other wire (blue with stripe), which flashes the side marker bulbs in phase with the turn signal bulbs.
With the park lamps on (headlight switch in either the first or second position), 12V is applied continuously on the brown wire. The blue/white wire provides ground through the turn signal filaments when the turn signals are off, and the side marker lights come on. When the turn signal switch is activated, the side marker on that side gets intermittent 12V applied on the blue/white wire. When 12V is present on both brown and blue/white wires, the side marker bulb goes dark. When the turn signal flasher opens, the side marker again grounds through the turn signal filaments and illuminates. In this case the side marker bulbs flash out of phase with the turn signal bulbs.
This same circuit has been used by Oldsmobile since the 1971 model year and it works flawlessly without relays or any other problems. If your bulbs are not operating this way, you have either a bad ground somewhere or a bad wire.
Ok I put aside for the moment the addition of relays.
But if it's the turnswitch in the steering column that's dead I don't rule out doing it because the customs fees for this kind of parts are terrible.
Looking at the diagram attached to my bay window in the living room, I ask myself an existential question:
in the image below, can you confirm that the bulb circled in purple is indeed the LH Side Marker and the bulb circled in green LH Cornering Lamps?
Should I be a smart A$$? Neither of those are "bulbs" - the bulbs are underneath the lenses. You have them exactly the opposite. A "cornering lamp" (circled in purple) provides a little more illumination during a cornering/turning maneuver; albeit, a cornering lamp has a clear lens. A "side marker" has an amber lens (circled in green). I believe this is a U.S.A. Federal safety mandate. Front side marker lamps must be amber, while rear side marker lamps must be red. I'm not privy on the Federal statutes governing the particular years of manufacture but I believe a 1978 motor vehicle required amber (front) and red (rear).
I finally found all the faults. Indeed the dried grease in the bases + HS filaments were already a source of problem.
But the real flaw is actually the turn signal flasher which is just dead. I reversed with the Hazards Flasher, and it worked impeccably well.
January 10th, 2023, 01:26 PM
