DigitalSynthesis

Just found this forum out... did a little searching to see if my problem had already been discussed but either it hasn't or I missed it so ...

I have a 1989 RX7 Convertible, and basically there are a few issues all working at once. When I hit the brake pedal with the headlights OFF, the dash lights come on as if the headlights were switched on, but the headlights do NOT come on. The brake lights work normally. When I turn the headlights on, all the brake lights (including the center light) come on at low power, then upon pressing the brake pedal operate normally. So, to summarize:

1. Headlights OFF, Brake Pedal PUSHED: Dash lights AND brake lights come on.
2. Headlights ON, Brake Pedal NOT pushed: all brake lights including center (high) light on dim.
3. Headlights ON, Brake Pedal PUSHED: Normal.

Can anybody give some clues as to where to begin troubleshooting this wierdness?

All help is much appreciated - I just bought this car, love it, but am a bit befuddled by this behavior.

Rxmfn7

iTrader: (4)

Look at your voltmeter when you tap the brakes, is it dropping down?? Sometimes flickering warning lights is a symptom of a bad alternator, and hitting the brakes makes it worse. It could also be a bad engine ground. Thats all I can think of for now. I think by dash lights you meant the idiot light cluster in the center above the A/C vents, right?

Icemark

I would double check the grounds at the lights as well as the CPU.

The CPU has a relay (the stop light warning relay) that sometimes sticks or has cold solder joints.

(one of the reasons I resolder everything when I rebuild a CPU).

DigitalSynthesis

Thanks for the input...

Actually, the problem isn't the idiot lights... its actually the entire dash lights and the parking lights!! Apparently the brake signal is getting shorted to the circuit labeled "TNS" in the wiring diagrams, causing the panel illumination to kick in and the parking/cornering lights to turn on. The CPU is not at fault (I unplugged it and the problem remains), neither is the headlight switch on the dash console. But this short explains all the problems... now if I could just find the d*mn thing...

I've checked all the under-dash wiring as far as I can inspect (excepting the plastic wiring bus lines and the massive clusters of wire running down into the floorboard, which I cannot easily access - besides, they don't look problematic right now anyway), and haven't found any evidence of where the short could be, but it has to be somewhere in the dash vicinity I think, unless there is separate wiring for the TNS and the brake lights running to the trunk, in which case the problem might possibly be in that area.

However, is the CPU wiring the connector on the bottom of the unit, or the connector on the front (the "big" one)? TNS goes to the "big" one, but I can't tell exactly what goes to the bottom connector.

Thanks a bunch - you guys rock!! Sorry for the slow response... I had a heater core hose blow up on me a few days ago and had to get a tow to the service station for a fix. That, and I've had lots of work between then and now.

Peace.. and thanks for any more suggestions you can come up with!.

DigitalSynthesis

Hallelujah! I figured it out!!! Some dumba$$ who replaced the taillight bulbs (not me!) put a single-brightness bulb in the dual-brightness socket, thus shorting the parking/running lights to the brake light circuit. SO glad it wasn't something cruel like a harness short! :-)

Peace...