Hello fellow Deville owners.

I am the original owner of my 98 Concours with 53K miles. The car is always meticulously maintained and pampered. I've done almost all of the routine maintenance and repairs since new.

However, I've run into an issue I can't seem to solve. The headlights and interior lights are flickering steadily when engine is running.

Voltage is 12.2 prior to start. DIC reading increases to 14.5 and then tapers off as expected. Currently reading at 13.5 at idle when warm (seems a little low).

I replaced the alternator with 100% new OEM Remy/Delco in July 2015.

Positive cable was pretty corroded, but cleaned thoroughly and cables appear to be in very good condition. Battery connections are tight. Flicker remains.

I cleaned both grounds that lead from the negative cable (didn't appear dirty at all). Flicker remains.

I have a brand new battery. Flicker remains.

I removed and tested all of lamp relays under the hood. All good.
I removed, inspected, and cleaned all of the fuses under the hood. All good.

I pulled the 18-month old alternator and had it tested at AutoZone. They ran the test 3 times, and it passed all three. (I've read this test may not be accurate, but this is new store with new equipment. ??)

Is it possible the alternator could still be bad?

Before I pull that sucker again (not fun), I want to look for any other faulty grounds. I have the GM Service Manual, but cannot locate the other ground points where the manual lists them.

Can anyone point me to precise locations of the body and engine ground points in the engine compartment? (I'm not concerned about the grounds in the trunk at this point. Can't see them being at fault since there are no other system problems.)

I've researched for hours, and tried everything I can think. So, I'm coming here for possible insight.

Thanks!

 

Check condition of both positive cables for corrosion under insulation. Positive battery posts would leak acid it could wick into wire. Also on occasion insulation would split along subframe to front junction block near underhood fusebox . Clean grounds. Check voltages at light bulbs see if feed voltage is erratic or ground.

 

Thanks. I did remove the red insulation from the positive and cleaned everything very well. Cable insulation and flex tube are all in tact along front frame. I need help locating any other ground points. Can't find them by following wires, and I've looked.

 

Those little wires on and around core support. If you look in section 8A there is a component locator and illustrations. I would check the voltage is stable at front fuse block and relay centers. you can try to add ground straps from engine to frame. There are several grounds in front where engine bolts to transmission.

 

Update...

While searching for grounds, noticed small amount of coolant leaking from bottom bolt of water pump. In process of changing gasket and pump now. Figured if I had to take everything apart, I may as well change the pump and belt while I'm in there. Cheap and easy to do.

Coincidentally, there is an engine ground directly below the thermostat housing. If coolant has been leaking there, this could be the whole issue. Fingers crossed. If not, I will proceed with checking voltage at bulbs.

 

Be sure to shield ABS unit from coolant. ABS unit is not coolant friendly it can cause connector issues

 

Finished installing new pump, gasket, pulley belt, thermostat, and full coolant change. If I hadn't had headlight flicker, I might not have noticed the water pump leak until it was a real problem. $77.00 and a few hours' time. Not too bad at all. (Probably only needed to change the gasket, but since everything was apart...)

Cleaned the large ground below the thermostat housing. Voltage now reads a constant 14.2 at normal engine temp. This is much better than before. Haven't driven in the dark yet, but I'm optimistic this fixed the issue.

Thanks for your help finding the grounds in the manual. (Those books are a maze.)

So, today the passenger seat stopped moving forward/backward. I hit 53K miles and suddenly everything is breaking! On to the next repair project...

 

its the age not the miles. It's 18-19 years old, my Eldo drove me crazy until it was totaled. Electric failures and many parts either way too expensive or discontinued. GM never built many Eldos, so they weren't high on the salvage yard save list.