SpecialEducation Posted June 7, 2016 Share Posted June 7, 2016 (edited) One of these days I'll get around to writing up a 'Me & My Buick' post on this 1989 LeSabre named Ruby that followed my dad home a couple weeks ago, but for now, here's what I know: 235K miles, runs and drives pretty nice. Nearly everything works, but shortly after getting the car my dad observed a funny noise so he gave it to me to shake down. I've put over 200 miles on it and I haven't heard any concerning noises, but the cruise control and air conditioning (electronic control) is driving me bonkers. First thing in the morning, everything works great, although I have noticed that cruise control does do a bit of oscillating when set around 45 mph. The drive home, however, is consistently a different story. I can set cruise, and it will work for a mile or two, then it just quits trying. The light stays on like it thinks it's engaged, but it isn't. If I hit the button to reset, it will grab for a second, then let go again. Once this happens, cruise control is done for the day. The light comes on, but no one is home. Also, the door that puts the air through the dash vents doesn't play nice in the afternoons. Sometimes it will pop within a minute of startup, sometimes it won't actuate at all. When it does pop, it is the noisiest air door I've ever heard. Bi-level and defrost both seem to work fine. With both problem systems being vacuum actuated, the first thing I did was check the condition of the vacuum lines. Everything looks pretty good, and I even pulled the line from the firewall can and there was still significant vacuum in reserve several minutes after shutdown, and this is after an afternoon drive with neither system functioning. That makes me think the two issues are coincidentally independent. As noisy as the air door is when it finally opens, it makes me think it's just sticky. Add to that the fact that there is sufficient vacuum to grab the throttle momentarily when I try to reset the cruise, it seems that its slipping condition isn't caused by lack of vacuum. Anyone out there have much experience with these systems? Edited January 3, 2017 by SpecialEducation (see edit history) Link to comment Share on other sites More sharing options...
FLYER15015 Posted June 7, 2016 Share Posted June 7, 2016 Matt, Find out where your car gets it's vacuum and hook up a "smoke pot", which you can make out of a coffee can, and it will show you leaks you cannot find any other way. Just google vacuum system smoke test, or do a youtube search. Mike in Colorado Link to comment Share on other sites More sharing options...
SpecialEducation Posted June 7, 2016 Author Share Posted June 7, 2016 (edited) To make it better, when I left work today, everything worked great. After 3 miles on the highway, the dash vents quit but cruise never missed a beat the whole way - adding to my suspicion that it's not a leak causing my cruise issue. Edited June 7, 2016 by SpecialEducation (see edit history) Link to comment Share on other sites More sharing options...
NTX5467 Posted June 10, 2016 Share Posted June 10, 2016 (I was thinking that the hvac uses stepper "actuators" to change the vents and such, but probably not?) IF the hvac system uses vacuum . . . the default mode f0r the vents is "Defrost/Floor heat", regardless of what the system commands to happen. This default mode happens when the basic vacuum supply to "the system" is either too weak or "not there". On many GM cars of that vintage, there is a check valve/vacuum tee near the power brake booster, with one line which goes to the cruise control actuator. Where the two lines meet at a right angle, there can be a fine, hair-line crack and things can still look fine. Usually, this leads to a non-functioning cruise control. It might be possible, in the early stages of "crack", that it might have some temperature sensitivity. The resultant vacuum leak is usually small enough that the ECM can put a little more fuel into the mix and the result might be a slightly less-smooth idle quality and a small drop in fuel economy. There is also, as I recall, a "power module" which is in the hvac ductwork under the hood. Similar in location to where the blower motor resistor array would go, but this is a power module (exposed transistor and circuit board, with heat sink) for the automatic hvac. Seems like there should also be a vacuum hose routing "decal" somewhere under the hood. It would show which lines go where and such, mainly for the engine items, but might have a little cross-over for the vacuum supply for the hvac system. Please keep us posted on what you find. NTX5467 Link to comment Share on other sites More sharing options...
SpecialEducation Posted June 10, 2016 Author Share Posted June 10, 2016 The funny thing is that I can put it on bi-level and it will switch the floor vents on, but still no dash vents. The recirc door also seems to work as intended. That makes me think the failure is between the control center and the door, or the door itself. If it's an electric actuator, that would narrow it down pretty quick. Now I just need to figure out where the door in question is located. Link to comment Share on other sites More sharing options...
NTX5467 Posted June 11, 2016 Share Posted June 11, 2016 Quote If this is a non-automatic a/c system, there will be a plastic "vacuum-distribution" valve which the "mode level" will rotate as it goes through its travel. This is where the main vacuum source ends up from the vacuum accumulator under the hood. It has a thin rubber gasket which seals it together, as the lower section slides when the mode lever moves. This valve is similar to the earlier pot metal valves of the middle 1960s era. On the metal ones, there was no gasket so the surface of the two halves had to be very smooth for things to work correctly. If you heard a "pop", that might indicate some binding somewhere with the vacuum actuators.' linkage. Might need to have somebody assist in moving the mode level, slowly with pauses to allow things to move, as you observe. If the system is the automatic system, there is a complex "controller" that runs the vent doors and such, to maintain hvac functions as desired. Please keep us posted, NTX5467 Link to comment Share on other sites More sharing options...
SpecialEducation Posted June 14, 2016 Author Share Posted June 14, 2016 (edited) Well, I'll officially declare the cruise and climate control systems as separate issues. I haven't had dash vents for nearly a week now no matter what I do, but the cruise has generally been decent 80% of the time. Since I've gone hard fail on the dash vents (but the floor vents for bi-level switch over perfectly), I popped the glove box down and pulled the hoses free from the programmer. When hitting the blue hose with source vacuum, the dash/defrost door flopped every time. I flipped the blue & orange hoses and now I have dash vents in auto again. Oddly, when I hit bi-level, I lose the dash and it goes back to defrost while the floor vents open up. I guess it's time to pull the programmer out and see if it's something I can repair, or if I'll dad will be buying a new programmer. Actually, it's time to go on vacation, so it'll be nearly 2 weeks before I get back into this... Oh, getting in there, I guess the recirc actuator is electric while the other doors are vacuum. I'll also note that all of the soft bits in the system are still quite soft and flexible, with no signs of cracking. Edited June 14, 2016 by SpecialEducation (see edit history) Link to comment Share on other sites More sharing options...
Barney Eaton Posted June 17, 2016 Share Posted June 17, 2016 Sometimes the cruise problem is the dump valve at the brake pedal.......it may be out of adjustment, leaking, cracked, etc 1 Link to comment Share on other sites More sharing options...
NTX5467 Posted June 18, 2016 Share Posted June 18, 2016 (edited) Quote Thanks for that additional information. NTX5467 Edited June 18, 2016 by NTX5467 (see edit history) Link to comment Share on other sites More sharing options...
SpecialEducation Posted January 3, 2017 Author Share Posted January 3, 2017 OK, I'm going to give this a bump. Neither issue seems to be vacuum related, so I'm going to be looking for some salvage components to get the gremlins out. Quick question: Where are the "brains" of the electronic climate control? Is the box on the dash just a remote control/display and the system logic (or lack thereof) is really in the unit below the glovebox? Link to comment Share on other sites More sharing options...
avgwarhawk Posted January 3, 2017 Share Posted January 3, 2017 (edited) Check the vacuum ball is not leaking or lost a line. Note this ball services the cruise control servo. Could be the reason for losing cruise as vacuum is exhausted over a short period of time. It appears to me a vacuum loss is your problem. The question is where. I suspect the vacuum storage ball. See diagram: Edited January 3, 2017 by avgwarhawk (see edit history) Link to comment Share on other sites More sharing options...
SpecialEducation Posted January 3, 2017 Author Share Posted January 3, 2017 19 minutes ago, avgwarhawk said: Check the vacuum ball is not leaking or lost a line. Note this ball services the cruise control servo. Could be the reason for losing cruise as vacuum is exhausted over a short period of time. It appears to me a vacuum loss is your problem. It is most certainly not a vacuum issue, I've beat that possibility to death. I just happen to have issues with 2 different systems that use vacuum. Link to comment Share on other sites More sharing options...
avgwarhawk Posted January 3, 2017 Share Posted January 3, 2017 Just now, SpecialEducation said: It is most certainly not a vacuum issue, I've beat that possibility to death. I just happen to have issues with 2 different systems that use vacuum. Check valves in the vacuum lines are functioning? Link to comment Share on other sites More sharing options...
SpecialEducation Posted January 3, 2017 Author Share Posted January 3, 2017 11 minutes ago, avgwarhawk said: Check valves in the vacuum lines are functioning? Yes. I had actually bought a new check valve, even though the system was holding vacuum for hours after shutdown, and the REPLACEMENT leaked - it whistled at WOT and at shutdown. On the upside, I had an audible indication of when I had more vacuum on the service side than on the manifold side, and there was never any whistling when the cruise would quit. On the climate side, I bypassed the controller, and my air doors hold all day long. It also does stupid things with the temp mixer, which has nothing to do with vacuum. The psychosis is in the controller logic. The cruise will start to oscillate before it fails completely. It starts out small and increases in amplitude, apparently until the error rate gets significant enough to cause the system to let go completely. It's not that it's slipping due to lack of vacuum, it is over-correcting and it seems to know it's doing so, so it quits. It will actually pull on the throttle pretty hard during the oscillations, but not hard enough to induce a whistle with the bad valve installed. There's plenty of vacuum available. Link to comment Share on other sites More sharing options...
avgwarhawk Posted January 3, 2017 Share Posted January 3, 2017 Possible the cruise control is losing data vehicle speed sensor thus shutting down? Link to comment Share on other sites More sharing options...
NTX5467 Posted January 5, 2017 Share Posted January 5, 2017 I suspect the reason for "the surge" is probably due to speed sensor readings vs "set speed" instructions. I've seen "the surge" on the earlier cruise units, BUT when they were on a body contact lift with the rear wheels not on the ground. With the car "in gear", the rear wheels will start turning. Once past the minimum "set" speed. when the cruise button is pushed, the cruise accelerates the engine. With no load on the drivetrain, the speed immediately exceeds the set point, so throttle is immediately reduced until wheel speed drops below the set point. Cycle repeat. That's "normal operation" with the wheels off of the ground. In looking in RockAuto, the cruise SERVO is under the hood. The cruise MODULE is probably under the instrument panel. The module is electronic but the servo is electro-mechanical with vacuum being varied to move the servo and throttle cable. The ONE check valve we saw the most "activity" on was the one near the power brake booster. It had a smaller port which supplied the HVAC, off of the same port that went to the cruise unit. The check valve function didn't fail, the small port CRACKED . .. cruise did not engage. The leak was big enough to not have enough vacuum for the cruise to work, but small enough that the ECM could cover the additional air with additional fuel. I saw lots of "ball" vacuum reservoirs get replaced, but not sure if that was the main problem. Many had a check valve inside of them. It might be time to seek out a wiring schematic for the cruise system for the SPECIFIC model year and BODY SERIES of your Buick. GM-supplied rather than "close match". The cruise modules which RockAuto has are "reman", as I suspect the servos are too. Might be that you can open them up and look for failed solder joints or similar? NTX5467 Link to comment Share on other sites More sharing options...
SpecialEducation Posted January 5, 2017 Author Share Posted January 5, 2017 I don't take the car out of town (which makes my kids sad), so the cruise isn't as irritating as it could be. The cold, however, is a bit obnoxious. At lunch today, I hit the exterior temperature button. It showed a bit warmer than expected. 1 Link to comment Share on other sites More sharing options...
SpecialEducation Posted January 5, 2017 Author Share Posted January 5, 2017 A couple hours later… 1 Link to comment Share on other sites More sharing options...
NTX5467 Posted January 6, 2017 Share Posted January 6, 2017 The exterior temp sensor is usually mounted on a front bumper support bracket near the bottom of the radiator area, but NOT attached to the radiator itself. Rather than an "air" temperature, it's a "contact" sensor out of free air flow. per se. It might sound a little flaky, but it works. Probably about the size of your little finger and "black", with a wire attached to it. Compared to some temp displays on signs, there can be a few degrees difference, but once "right", your's seems well within spec. Now, IF that sensor is accurate, that's one heck of a cold front headed toward TX! NTX5467 Link to comment Share on other sites More sharing options...
SpecialEducation Posted January 6, 2017 Author Share Posted January 6, 2017 1 hour ago, NTX5467 said: The exterior temp sensor is usually mounted on a front bumper support bracket near the bottom of the radiator area, but NOT attached to the radiator itself. Rather than an "air" temperature, it's a "contact" sensor out of free air flow. per se. It might sound a little flaky, but it works. Probably about the size of your little finger and "black", with a wire attached to it. Compared to some temp displays on signs, there can be a few degrees difference, but once "right", your's seems well within spec. Now, IF that sensor is accurate, that's one heck of a cold front headed toward TX! NTX5467 When I first hit the external temp button, it said 24° (I work at the airport, so airport temp of 18° actually means something to me). I drove 1 mile and the temp shot up almost 100°. If that's in spec, that's quite a tolerance they've given it. Link to comment Share on other sites More sharing options...
NTX5467 Posted January 7, 2017 Share Posted January 7, 2017 I believe that a 5 degree variance would be the max spec, but some customers see a temp on a bank display and believe that their vehicle should indicate similarly. In many cases, only a few degrees off, but not the magnitude you mention. Different banks, different temps indicated! It was a solid 22 degrees today, going down to about 16 degrees tonight and Saturday night. Only about 5 hrs forecast to be above freezing over the next day or so! That's pretty cold for us! I suspect the thermistor in the sensor is a resistance device That would make integrity of wiring connections important. Never have seen any specs for the resistance vs indicated temperature, though. Might be a "decoder" module in the instrument panel unit? The RegalGS forum had some information on how to repair the display of their auto temp instrument panel unit (mainly dead sections of the numbers display). Perhaps there might be something in their forum about the outside temp display? NTX5467 Link to comment Share on other sites More sharing options...
JohnD1956 Posted January 7, 2017 Share Posted January 7, 2017 That outside temp sensor was one of the first things I had to replace on my 95 Riviera. Since mine was way off the HVAC would not heat or cool correctly. But the doors for directing the air to the vents still worked. Link to comment Share on other sites More sharing options...
SpecialEducation Posted January 10, 2017 Author Share Posted January 10, 2017 On 1/6/2017 at 7:37 PM, JohnD1956 said: That outside temp sensor was one of the first things I had to replace on my 95 Riviera. Since mine was way off the HVAC would not heat or cool correctly. But the doors for directing the air to the vents still worked. Well, that may explain the mixer door psychosis, but not the floor/dash control. A couple of these have shown up in salvage recently, and I'm wondering what parts I should be stockpiling. I guess I'll add temp probes to the list... Link to comment Share on other sites More sharing options...
JohnD1956 Posted January 10, 2017 Share Posted January 10, 2017 I'd check NAPA and or the dealer. The new one was less than $20.00 Why go through the work to salvage one with the same wear and tear as the one you have? Link to comment Share on other sites More sharing options...
NTX5467 Posted January 11, 2017 Share Posted January 11, 2017 There are some items which can be best "new" rather than "harvested new". But, if the salvage yard person doesn't see the sensor as a "big seller" or "in demand", it could be very inexpensive! Might also end up being more "universal" in GM than suspected, too! NTX5467 Link to comment Share on other sites More sharing options...
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