Automobile(s): 1985 Sedan DeVille Join Date Aug 2007 Location Southern Maryland Posts 1,559 Re: 85 c

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1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum 85 cruise control diag and parts interchange CadillacForums.com is the premier discount hotels montreal Cadillac Forum on the internet. Registered Users do not see the above ads.
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, 85 cruise control diag and parts interchange in Past Cadillac Vehicle Discussion; The cruise discount hotels montreal control went out on my 85. Basically it won't hold speed but I can feel a very slight ... LinkBack LinkBack URL About LinkBacks Bookmark Share Digg this Thread! Add Thread to del.icio.us Bookmark in Technorati Tweet this thread Cadillac Discussion Tools Show Printable Version Email this Page Subscribe to this Thread 08-28-10 05:39 PM #1 ehall
Automobile(s): 1985 Sedan DeVille Join Date Aug 2007 Location Southern Maryland Posts 1,559 85 cruise control diag and parts interchange The cruise control went out on my 85. Basically discount hotels montreal it won't hold speed but I can feel a very slight sputtering like something is trying to work and failing to hold.
From what I can glean, the system uses a relatively complex vacuum assembly to manipulate a diaphragm, which is in turn attached discount hotels montreal to an arm that is also connected to the throttle body. The car uses a speed sensor on the transmission to monitor the desired output speed, then modulates the vacuum pressure going into the diaphragm to try and maintain the desired discount hotels montreal output speed by opening and closing the throttle body.
The vacuum assembly seems to be where my problem is located. First there is a basic vacuum solenoid which acts as an ON-OFF filter for vacuum pressure--when discount hotels montreal the system is engaged it allows vacuum discount hotels montreal pressure to pass to the rest of the assembly, but when the system is off it directs vacuum through a bleeder valve. I have monitored this part with a vacuum gauge and it seems to work fine: when the system is off there is no pressure on the output port, but when the system is on the pressure discount hotels montreal immediately jumps up to ~17 hg inches and stays there until it's turned off again.
Next in line is the power solenoid which controls the amount of vacuum pressure that is passed to the diaphragm (this is what actually controls the linkage discount hotels montreal movement). discount hotels montreal I have also tested this part with a vacuum gauge and it does NOT work as expected. According to the FSM it should vary the amount of vacuum, but when I hook the gauge to the output port (which is usually plugged into the diaphragm) I see sporadic blips of vacuum pressure, usually low or off then ON full then low or off again. It does not appear to be trying to maintain discount hotels montreal pressure at all. Also the spikes seem to correlate with the sputtering. discount hotels montreal I am pretty sure this is my problem.
I don't know if the unit has failed or if the signal to the unit is bad. The FSM doesn't tell me how to test the signal from the ECM so I don't know how to check. Also I cannot find the unit at any parts stores. It seems that ~84 and earlier used a different vacuum setup, while ~87 and up use an electronic diaphragm. I will probably try to find one in a junkyard and see if I can get one to work.
I assume somebody else ran into into this already so if anybody has any ideas or inputs on this let me know pls Share Share this post on Digg Del.icio.us Technorati Twitter Reply Sponsored Links Remove Advertisements CadillacForums.com Advertisements
Automobile(s): 1985 Sedan DeVille Join Date Aug 2007 Location Southern Maryland Posts 1,559 Re: 85 cruise control diag and parts interchange The FSM describes a way to make the solenoids flitter on and off, so I did that while listening discount hotels montreal with my mechanics stethoscope ( here is a blog post by noahsdad describing this exact process). Once the test starts, I can clearly hear the power solenoid clicking like crazy, so I assume everything discount hotels montreal is working correctly from an electrical perspective, and the mechanical part of the solenoid is probably damaged.
I wonder if this is the same setup on all 85-86 GM cars. I can't find anything for any of them but I notice that the 84 DeVille interchange is basically every other 84 GM Share Share this post on Digg Del.icio.us Technorati Twitter Reply 08-29-10 07:21 PM #3 dennis93coupe
Automobile(s): 1993 Coupe Deville 2006 XLR Infrared, 2009 XLR-V Crystal Red Join Date Feb 2010 Location Orange County, CA Age 60 Posts 2,468 Re: 85 cruise control diag and parts interchange My factory parts book covers discount hotels montreal 85 Deville and up. What exactly are you looking for? I can't tell you what interchanges, but I can give you a parts number that might have changed since June of 1993. Share Share this post on Digg Del.icio.us Technorati Twitter Reply 08-29-10 11:41 PM #4 ehall
Automobile(s): 1985 Sedan DeVille Join Date Aug 2007 Location Southern Maryland Posts 1,559 Re: 85 cruise control diag and parts interchange The FSM calls it a cruise power solenoid , it's the vacuum solenoid that plugs directly into the back of the diaphragm. Share Share this post on Digg Del.icio.us Technorati Twitter Reply 08-30-10 02:55 AM #5 dennis93coupe
Automobile(s): 1993 Coupe Deville 2006 XLR Infrared, 2009 XLR-V Crystal Red Join Date Feb 2010 Location Orange County, CA Age 60 Posts 2,468 Re: 85 cruise control diag and parts interchange Ok there is item
I didn't ask or read your whole post, but this isn't a diesel is it? It's a 4.1L right? Hmm, had a vacuum pump then huh....Also this covers 1985-1987 C body if that helps. Share Share this post on Digg Del.icio.us Technorati Twitter Reply 08-30-10 11:02 AM #6 ehall
Automobile(s): 1985 Sedan DeVille Join Date Aug 2007 Location Southern Maryland Posts 1,559 Re: 85 cruise control diag and parts interchange Originally Posted by dennis93coupe discount hotels montreal 7, GROUP 3.885 SOLENOID, CR CONT PART #25031699 (price about $92.25 in 1993) That's the one, confirmed it a couple of different ways
Automobile(s): 1985 Sedan DeVille Join Date Aug 2007 Location Southern Maryland Posts 1,559 Re: 85 cruise control diag and parts interchange The good news is that a nearby junkyard just got an 87 so I was able to grab the cruise parts from it, along with some other stuff I've been hunting.
This got me irked so I did some more diagnostics work. There is a vacuum test in the FSM that supposed discount hotels montreal to tell you if the solenoids are working, basically you put 12v to each solenoid with the engine running discount hotels montreal and car in Park, and the solenoids should both open and allow unrestricted vacuum to the diaphragm which will cause it to pull the linkage and rev the engine. This works as described, which means that my problem isn't with the mechanics at all. That means the problem is with the signal, either with the wiring discount hotels montreal or with the actual signal from the ECM.
When I did the solenoid tests described earlier, I could hear the power solenoid flickering on and off, so I know it's getting signal. In addition, the system won't power up if the power solenoid is disconnected (the car sees the open circuit and refuses to engage the cruise control). This all means the circuit must be good.
So the only thing left is the signal from the ECM? Maybe there is a problem with a sensor or switch discount hotels montreal that is preventing the ECM from engaging the cruise control? I did a switch test earlier that showed all of the switches were working so this shouldn't be the problem. Maybe the Park/Neutral switch (I did some work on the shifter recently)? Maybe the transmission speed sensor (the diag shows the digital speed signal but I don't know if that's the same input)? Any other ideas? edit : talked to my mechanic buddy and he said there is a vacuum release switch at the brake pedal that vents vacuum from the diaphragm and if that is leaking discount hotels montreal then it will do what I'm seeing. I have to get a hand pump and will test this out! Share Share this post on Digg Del.icio.us Technorati Twitter Reply 09-03-10 12:09 AM #8 dennis93coupe
discount hotels montreal Automobile(s): 1993 Coupe Deville 2006 XLR Infrared, 2009 XLR-V Crystal Red Join Date Feb 2010 Location Orange County, CA Age 60 Posts 2,468 Re: 85 cruise discount hotels montreal control discount hotels montreal diag and parts interchange You said you did some work recently on the shifter. On the column? You don't think it's the turn signal lever/cruise switch? Share Share this post on Digg Del.icio.us Technorati Twitter Reply 09-03-10 01:32 PM #9 ehall
Automobile(s): discount hotels montreal 1985 Sedan DeVille Join Date Aug 2007 Location Southern Maryland Posts 1,559 Re: 85 cruise control diag and parts interchange I figured I would try to get a look at the vacuum vent switch on the brake line, so started tracing the line and cleaning some connectors. The line in the engine bay looked alright so I popped the trim from under the dash and looked discount hotels montreal at the brake switch assembly. There are multiple switches here, one of them is a vacuum switch that connects to the diaphragm, so that the vacuum in the diaphragm will be vented when the brake is pressed. The vacuum line there also looked good (looked great actually, still smooth and not at all dry). I couldn't really see too well but I could feel a plunger that opened when the brake was pressed. Everything seemed normal. discount hotels montreal Maybe a leak in the line somewhere under the dash?
I figured out a way to test for vacuum, by connecting the main harness directly to the brake hose and watching my gauge while tapping the brakes. Sure enough, the line went up to ~17 hg inches then dropped discount hotels montreal to 0 whenever I pressed the pedal, so the vacuum switch was venting discount hotels montreal the line as it should. No leaks, no problems... Then I went for another drive and now the cruise control works! My guess is that the vacuum switch was stuck open a little bit and by brushing it with my finger I unstuck it. Share Share this post on Digg Del.icio.us Technorati Twitter Reply 09-03-10 01:43 PM #10 ehall
Automobile(s): 1985 Sedan DeVille Join Date Aug 2007 Loca