headlight/parking light issues- 1970 ambulance

[John Zicha]

We have our 1970 Cadillac superior ambulance running and driving again. She is quiet, purrs like a kitten and drives very nicely.
When our mechanic shop started working on it, the headlights/market lights etc. all worked. They pulled the engine and trans and replaced it with a known running unit, replaced all the brakes and suspension. Now when you connect the battery (turn on the master switch) the left rear brake light illuminates and so do the rear license plate lights. When you pull out the headlight switch, the dash lights illuminate and so does the right blinker light (constant on), but no lights on the exterior of the car come on at all. I'm thinking there might be a ground wire somewhere that might not be corrected?? I'm trying to figure out where to look first. I also see a button hanging under the dash. I looked it up and its called a brake light switch? I attached a pic of it.
Thanks for any help.

[Bill Marcy]

Hi John, I will throw a couple of thoughts out, but this is just from my experiences over the years, perhaps somebody who is an expert will have better ideas.
1 Check the dimmer switch, sometimes they go bad, sometimes they have corrosion on them. It sounds odd, but I had a somilar problem with a 68 Cadillac.
2 Check/replace your directional flasher and your four-way flasher boxes, sometimes they cause strange problems with lights.

Let's see some pictures of your ambulance, we love pictures!

[John Zicha]

The dimmer seems fine. Dims lights on dash. When I push in the brake light switch, the one light that always stays on shus off.

[Jacob M. Fournier]

Originally Posted by Bill Marcy

1 Check the dimmer switch, sometimes they go bad, sometimes they have corrosion on them. It sounds odd, but I had a somilar problem with a 68 Cadillac.

Originally Posted by John Zicha

The dimmer seems fine. Dims lights on dash. When I push in the brake light switch, the one light that always stays on shus off.

Bill wasn't referring to the the dash light dimmer, but the floor mounted switch that dims the headlights (low beam / high beam) - the location of the switch in the floor means that they have a tendency to build up corrosion and cause headlight issues.

The rear brake light is staying on because that brake light switch is loose - it mounts in a bracket up under the dash, close to the base of the brake pedal. When the brake pedal is not being pushed, and the spring returns it to it's normal position, it will push and hold the button in on the brake light switch, keeping the brake lights off - when you step on the brake pedal, the button is released, sending power to the brake lights. As to why only one is on, could be as simple as a bad bulb on the other side, or a wiring issue, or an issue with the directional signal (the directional signals use the same element in the bulb as the brake lights, but have priority over the brake light.)

[John ED Renstrom]

they left a ground strap of the engine. these late morale ones it's more impotent then ever. if every thing worked before the engine swap it had to be something done during the engine swap. the ground strap is the most likely thing. remember the light bulb doesn't care which way the current flows threw it. so now you know the grounds on that set of light are vary good. a set of jumper cables is all you need to prove it. connect the engine to the neg side of the battery with them and to the body with the other set of clamps. if the problem goes away or changes you know were to look.

[John Zicha]

Thank you very much. I was thinking a ground of some sort myself. I just didn't know if there were little ground wires that were originally to the engine area that might have been over looked when the new engine was put in.