turn signal cancels cruise

Audiovox 250-1316 unit cancels when the turn signals are used. I guess the turn signal activates the 12v signal the same as the brake light would. Is there a work-around for this with a dual filament park/stop bulb setup (in a '51 chevy)? Or is the brake cancel set up on the wrong side of the brake switch?

You likely have bad connections in your brake light circuits. The violet wire that connects to the switched brake light wire, must see ground on it until the brake pedal is applied. On some older vehicles, connections become poor and the resistance to ground increases. You should first check that all your stop lamp bulbs are working. Having one or more out can cause the same problem. You can wire in a relay to the circuit to fix the problem. Just remember that the relay will click every time the brake pedal is applied, so bury it somewhere that you won't hear it. Connect the switched wire off the brake switch to terminal # 86 of a SPDT relay. Terminal # 85 and # 30 go to ground. Terminal # 87a goes to the violet wire of the cruise control. Terminal # 87 is not used.sparky

Thanks Sparkie, I will check out all that you recommended. Just so I understand, in a properly wired cruise setup, the turn signal should not cancel the cruise. Is this correct? If the turn signal will cancel the cruise in a properly wired cruise, then the only cure will be a relay. Is this correct? Thanks for taking the time to reply.

The turn signals shouldn't cause the cruise to cut out. It happened on some old cars back in the olden days. The fix back then was to add a resistor to help the cruise control see a better ground reference. I believe the value may have been about 10k ohms. I would suggest the relay method is preferable though, unless you can resolve the problem in your brake/signal lamp circuit. The violet wire for the cruise shouldn't have more than 10 ohms resistance to ground on it unless the brake pedal is depressed. This value shouldn't change when using the turn signals.sparky

If you are happy with the way the blinkers are working, brightness etc.  A diode in series with the brake wire, between the point of connection of the cruise control and the lamp itself will eliminate your problem.

Thanks Sparkie and I Am An Idiot, a friend and I went over the lighting system yesterday and think part of the problem is that the car has LED bulbs in the rear which we suspect may be causing some of the problem. We have two regular blubs to compare. We cannot find any other problems with the lighting circuits except with the LED's in and the cruise powered we get problems. Oddly enough my friend called last night and suggested a Diode in the violet wire to the cold side of the brake switch. This is the only place the cruise and the lighting system are common. Thanks for your interest! I will let you know how all this works out.

The LED brake lights are the problem. I installed a cruise on a customer's hot rod and a year later he converted the tail lamps to LED's and the cruise wouldn't work. They don't allow the violet wire to reference a proper ground because there is no longer a filament. Trust me. Install the relay. The diode will only make matters worse.sparky

Well, Sparkie, you win the prize! I finally got through to the Techie at Rostra and he said go with the relay. And he took the time, probably realizing what a moron he was dealing with, to explain what the circuit was doing. What I didn't understand was that the Violet was looking for ground through the brake return circuit, not 12 volts. The LED's do not show ground through the circuit. I thought it was looking for voltage when the brakes were applied. The wiring diagram does not make that clear. When cruise is engaged, Violet is wanting ground all the time except when the brake circuit is energized and that causes the ground to be interrupted and kicks out the cruise. The relay is wired as follows: 85 - Violet from Cold Brake wire 86 - Ground 87 - Not connected 87A - Violet from Cruise Box 30 - Ground (87A and 30 are normally closed) Now the relay is using the 12 volts to energize the relay (85 & 86) and the other side is interrupting ground when it is energized (87A and 87 connected but open). Thanks again for taking the time to get involved. This is what makes fooling with old cars interesting.

This concludes this lesson. I am happy to hear you got it working.sparky

Just a footnote, the Diodes in the brake return circuit did solve the voltage bleedover problem in the turn signal circuit. We even left the Diode in the cruise Violet for protection. It does not hinder the cruise operation.