[DeTomaso] More cruise control issues

Christopher Kimball chrisvkimball at msn.com
Fri Sep 11 02:31:13 EDT 2009


This evening I did what was suggested by the last tech with whom I spoke.  First, I tried the sensitivity switches in all their different positions.  The difference between high and low sensitivity was barely noticeable.  Then I fashioned an extension arm on the throttle so the cruise control cable would have more travel and therefore more leverage to move the throttle.  The technician thought this might help in a high-horsepower/low weight scenario. 

The extension arm may have made a little difference, but the thing still cycles annoyingly.  This weekend PNW is going on a weekend trip with some freeway driving, so I'll get a chance to see if it's bearable or not over longer time periods.  If not, the next step is to find an oscilloscope and do the tests you recommended below.

Sincerely,

Chris



From: SOBill at aol.com
Date: Thu, 10 Sep 2009 00:58:04 -0400
Subject: Re: [DeTomaso] More cruise control issues
To: chrisvkimball at msn.com








Chris,
 
The number of pulses per mile is not really critical to a 
cruise control. Whatever number of pulses being produced when you hit 
the SET SPEED button, represents the number of pulses the cruise control will 
try to maintain with the throttle. If the number of pulses drops below the SET 
SPEED number of pulses, the car will accelerate. If the number of pulses goes 
above the SET SPEED number of pulses, the car will slow down.
 
If the pulses are erratic, then you will have a 
problem.
 
I would find someone with, best case, an oscilloscope so you can 
see the VSS output from the sender. It should be a solid square wave directly 
proportional to wheel speed. If no oscilloscope, see if you can find someone 
with a multimeter which has a frequency  measuring function.  many 
small, inexpensive multimeter have frequency function these days. Connect the 
meter between VSS and ground. The frequency should be stable at a constant wheel 
speed and increase with increasing wheel speed. This testing is dead easy on 
jack stands.
 
Wish I was near enough to help.
 
Let me know what you find,
 
SOBill 
Taylor
sobill at aol.com 
 
 


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