Cruise

Hello all
My name is boyd and am from Paisley Scotland.

Electronics has never been a strong point with me but I am a dab hand with relays, timers, diodes etc. as required in connection (no pun intended) with my job as an electrician.

My hobby is building/rebuilding cars and kitcar type vehicles and solving all issues that arise.

However, for the past year I've been tinkering with my cruise control in my latest kit which is based on an old Mercedes. To say it is driving me nuts would be an understatement. I've replaced the amplifier (ecu) with 2 spares at cost each time and am aware that they are unreliable. The system wiring, speed sensor, actuator etc. are all in good order.

I know that by this time you will be thinking I am on the wrong forum, but hold on. I need some advice from somebody infinitely more clever.

A cruise amp seems to be a mass of electronics on a pcb but performs basic functions. Can I make one at home with readilly available components?

Functioning as follows,

Automotive, therefor 12-14v.
Takes a signal from a speed sensor of 50-155hz (at 7v steady)
(50hz is 30mph and shouldn't operate below that speed)
Operates a set of clean contacts to drive the actuator to accelerate.
Ditto above...............................................................decelerate.
Tries to match/maintain the hz signal received when 12v is applied to the pcb.(switched on at the column)
(obviously the hz signal is relative to the desired cruise speed)
The speed signal will always be there even if the unit is not required to operate so mustn't be able to do any damage via return path to permanent negative or switching would need to be D.P.
I am not concerned about 'resume' function.

All other stuff can be taken care of externally with relays. I.E. brake pedal drop out, polarity reversal for actuator deive, actuator clutch (engage) mechanism and refusal to work in neutral (only in drive).

Any info, help, assistance would be most welcome.



Boyd

Would it be possible to disassemble one of the old ecu control units?
There is a distinct possibility that the problem with the defective units is an aged or malfunctioning component that can be replaced. Electrolytic capacitors are notorious for this characteristic. Since you have more than one non-working ecu, maybe the identical part is causing the units to fail.

Hi friend,
Thanks for looking.

I have 3 units.

No knowledge is my problem with these units as all looks in order within. a
They are dipped inn varnish and show no signs of burning.

I can send them to Holland for repair at a cost of 110 euros plus post but they are known to be unreliable so I could end up in the same position soon after.

Boyd