[DeTomaso] More cruise control issues

[Chris Difani]

Chris:

I guess the other question to ask here, is the VSS you got from SOBill "good"?  Was it in service in a working correctly cruise control?  Or did it come to you "new"?  I'm wondering if that might be the source of the surging?  If it's bad "out of the box failure", then you might want to try another one...  I've got one myself, but it's the kind that's designed for an electronic speedometer only.  It's only got 3 wires coming out of it, ground, 12V+, and signal.  You're welcome to try it, but I can't say it's perfect... (because I'm not "on the road" yet).

Just a thought....

Chris

Chris Difani
'73 L #5829 "LITNNG"
The Electric Pantera
Sacramento, CA
Email: cdifani at comcast.net 


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----- Original Message ----- 
From: "Christopher Kimball" <chrisvkimball at msn.com>
To: <sobill at aol.com>; "Pantera List Serve" <detomaso at realbig.com>
Sent: Thursday, September 10, 2009 11:31 PM
Subject: Re: [DeTomaso] More cruise control issues


> 
> 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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