Odd behaviour with brake lights and Waeco Cruise control

[Fredanz]

Gidday,
This is just a report in case it helps someone else in a similar situation.

Vehicle:
Freda '97 with Waeco Cruise control added long ago, working fine

Problem:
Recently, my ignition barrel failed (internal fracture!) and was replaced. This is not relevant except it made me think the problem was related to that. It wasn't.

Soon afterwards I noticed two things:

1. The cruise control would drop out, i.e. I'd be cruising along, then suddenly slowing down because it had disengaged by itself

2. It was at least a month before I noticed the second issue when I was parked in front of some windows - when the brake pedal was pressed, the PARK lights came on! Something clearly amiss there.

Solution
To cut a long story short, the fault was caused by a bad bulb in the brake lights. It was somehow shorting through to the park lights and in some way (I assume) also affecting the voltage that the Waeco uses to determine whether the brake pedal had been pressed. [Haven't yet tested that the latter issue has gone away, but I'm pretty confident].

Me, I thought they'd slightly stuffed up the ignition replacement somehow. But replacing the bulb has sorted it.

I'd seen something a bit similar mentioned in the "brake lights" topic in March, but didn't twig because, to my casual inspection, the brake lights looked as though they were functioning fine.

We live and learn.

[westonwarrior]

When you say park lights do you mean the reversing (white)light?

or do you have a seperate light in NZ foir use when parked?

[David Edwards]

Nice one Fred well worth remembering, happy motoring.

[jaylee]

I think Fredanz means the tail bulb..?
I've seen a similar thing with following old Fords... (Mainly Escorts.)
Some times when they indicate the tail light (& indeed brake light) dims & brightens with the indicator flash..

[Fredanz]

When you say park lights do you mean the reversing (white)light?

What I call the "parkers" are the low-illumination white lights facing front and similar low-illumination red lights facing to the rear (first click of the lights stalk).

At least the former went on with the brake, I dare say the latter did too, due to a current leak across one of the stop/rear-parker bulbs. The bulb had been replaced last month, i.e. was new, but faulty.

[bigdaddycain]

I understand, sounds like a crossed circuit within the bulb, (maybe the smaller filament arcing across the bigger filament within the twin filament brakelight/sidelight bulb).

Well done making the correlation between the light fault and the cruise control irregularities!

Jaylee was right, late 90's fords were plagued with light faults due to a dodgey earth to the rear left light cluster.