Brights not working...

Gregg Benedict

Gregg Benedict

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The brights are not working on my '68 Imperial I just received. It seems highly unlikely that all 4 bright elements are out. I suppose it might be the foot switch, or possibly something with the relay, but not sure...

-Gregg B.
 
Most likely it's the dimmer switch, it's a common failure point.

I know this goes against conventional forum logic of spending someone else's money, but rather than just throw parts at it, testing is quick and easy and will show you how it works. (With apologies to anyone that has correctly suggested to change the switch)

It's very easy to check. Disconnect the plug at the switch. You'll see 3 wires. The green wire is the feed from the switch. Turn the light switch on. With a short jumper wire, connect the jumper from the green to each of the other connections, one at a time and check for operation. If the lights work, it's the dimmer switch.

You'll need a couple of these and a length of wire. Toss it in your tool box when done as part of your Mopar electrical diagnostic survival kit.

63677.jpg
 
Gregg Benedict said:
When you say dimmer switch, you mean the floor switch, not the dash light dimmer switch, right?
Click to expand...
Yes. That is the headlight dimmer switch, meaning it changes the headlights from high to low, thus dimming them.
 
Big_John said:
Yes. That is the headlight dimmer switch, meaning it changes the headlights from high to low, thus dimming them.
Click to expand...

I haven't dug into it yet, but I did suspect the floor dimmer switch. This is my first Imperial and the first time I'm dealing with the Sentry Sentinel lightning and such... was just making sure I didn't miss anything. I'll check with a jumper later on today. Thanks for all your help...
 
Gregg Benedict said:
I haven't dug into it yet, but I did suspect the floor dimmer switch. This is my first Imperial and the first time I'm dealing with the Sentry Sentinel lightning and such... was just making sure I didn't miss anything. I'll check with a jumper later on today. Thanks for all your help...
Click to expand...
This is completely separate from the Sentinel system.
 
So... I got around to getting a new switch. The thing is, it is doing the same thing. When I disconnect the switch, I have brights. When I hook it back up, I only have the regular headlights. Pushing the dimmer switch does nothing to change it. Now I'm suspecting the headlight relay, but I'm not sure about that either...
 
Well, I'm in a quandary on this one. It turns out I have a 4-prong dimmer switch, likely because the car has the automatic headlight beam changer. But, the 4th prong looks like it is for the photo-amplifier located on the cowl. So, I should be able to bypass that. But, like I said earlier, replacing with a new 3-prong dimmer switch does nothing. The only way I can get the brights to work is to disconnect the switch entirely. So... does anyone have any ideas? Maybe I should ask if anyone has one of those 4-prong dimmer switches available?
 
Does anyone know how many amps run through the dimmer switch? I'm thinking of a Rube Goldberg where I'm partially bypassing the foot switch with another switch...
 
When I posted my comment on how to test, I had zero idea that there was a "Sentinal system" involved. Sigh.... Always include such information. It makes things easier on everyone and wastes a lot less time.

Have you looked at the service manual?

I just looked at my '70 FSM real quickly and it shows how to check the system. I don't have a '68 FSM, but I would bet that it all works the same. I would go through the steps there first. Can't beat them for figuring out the problem. That floor switch can't be that hard to find... IF you need one that is. Just can't get one at Advanced Zone. Somebody will have one.

That said, from looking at it quickly, I think the Sentinal system could be bypassed and it wouldn't even surprise me if the connector to the system plugged directly into a conventional dimmer switch. Don't even think about reaching for a pair of dykes to snip wires until you've really looked at what's going on though. I'll bet it could be bypassed by just unhooking some wires, but I know nothing of how this is actually installed, I'm just going by past experience.
 
Not Sentinal, auto dimming headlights.
 
detmatt said:
Not Sentinal, auto dimming headlights.
Click to expand...
So, he doesn't have the Sentinal system? As I said, I don't have the '68 manual so I don't know and not familiar enough to help much.

I would still think it would be covered in the FSM though...
 
He might have the headlight Sentinal but that’s separate from the auto dimming feature.
 
I actually have both on my Imperial... Safe Guard Sentinal and Auto Dimming. As I mentioned before, the switch actually has 3 wire blade prongs in the front - as typical, plus an additional prong in the back. The standard 3-wire pigtail hooks in the front, with an additional single wire in the rear. I assume the back wire is associated with the Sentinal or Auto-dimming, but I'm not positive. I do indeed have a '68 service manual and have tried to troubleshoot the problem there. However, there is nothing in the manual that referrs to having brights when the switch is connected, and no brights when the switch is hooked up. As I also mentioned, I did get a new switch (3-prong) on ebay, as it is logically the weakest link in the system. However, the same exact problem exists whether I use the old switch or the brand new one.

And, I have yet to see a 4-prong switch for sale anywhere...
 
OK... thanks for that. I couldn't find a 4-prong anywhere. Now, I guess I have to hope it IS the switch that is bad...
 
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