That is complete bullshit and does not indicate normal behavior. Do you think that the engineers did not take the vacuum drop typical with hard load or acceleration into account when they designed it? What this does indicate is either a defective check valve (used to prevent those vacuum changes from effecting air flow) or a vacuum leak after it.
That is complete bullshit and does not indicate normal behavior.
Its been normal behavior in Chrysler vehicles since the early 70's, my Dart does it, my Cordoba does it, and my LeBaron does it. The only vehicle I have that doesn't do it is the Ram, and thats got a vacuum pump on it instead of engine vacuum.
This is another case of you spouting off without thinking.
For someone who vehemently questioned the engineering of certain electrical circuits when queried about a voltage drop, your faith in their ability has certainly improved.
Have fun chasing down a vacuum leak etc. For the amount of time you put into trying to make a system perfect, you'll realize that this minor imperfection is normal.
Usually it's a cracked hose. Most AC systems have a small reservoir somewhere and a check valve. No idea what a van has.
Al
AC systems have no reservoir for vacuum. The entire vacuum system has a reservoir, which may or may not be big enough to counter a WOT application, particularly on a van application. Thus, since the reservoir is for the entire system not just the HVAC controls, it is entirely possible that fluctuations in the system will show up as momentary changes in how the HVAC doors are positioned.
Obviously a diesel Ram would be different, since no engine systems use vacuum, unlike the gassers. Obviously since this is a van, it hasn't got a diesel.
It is interesting to note that the troubleshooting section on the HVAC vacuum system claims that a system that works well at idle may not work well at high engine speeds.
Meanwhile, you two are suggesting vacuum leaks and such as the cause. You are aware, I hope, that a vacuum leak would cause the HVAC controls to operate erratically most of the time, not just at low vacuum events. Also, if the vacuum system has a leak, some sort of loss in performance of the engine would result. Most likely symptons would be loss of power, stumbling or backfiring.
But I'm sure you both know better than me, at least in your own minds.
So you are comparing relics from the 70's to a modern truck?!?!?!?! My 97 does not have a vacuum pump and it never does that and come to think of it, neither did either one of my Magnums (78 and 79).
Me, LOL, PKB.
Once again resorting to spin I see. I never claimed that the engineers were at fault for the undersized wiring, that would be you in your lame attempt to cover for not understanding a simple voltage drop.
imperfection
Just because something is difficult to find doesn't make the problems it causes normal unless of course, you suck as a mechanic and use crap like this as an excuse not to try and fix it.
Your 97 wouldn't have a vacuum pump, its not a diesel. To most of us that actually know somehting, this fact would have been obvious.
Might be why you aren't a mechanic, and instead think a vacuum system is perfect all the time.
If you actually know mechanical systems, you would know that a vacuum system is the most difficult to keep leak free and also the most difficult in which to find the leak. Further, you would know that a perfect vacuum can cause as many problems as a system that has too big a leak.
Obviously since you decided against arguing with my technical fact, you've got nothing of actual facts for a rebuttal.
Good luck with your credibility.
LOL, are you really this desperate??? Who am I kidding, of course you are. I am well aware of why my truck does not have or need one and my point was that even without it and depending on nothing but engine vacuum my climate control is working exactly as it is supposed to, without airflow interruption due to either acceleration or heavy load. If you had the knowledge you claim to then you would be able to argue on valid points instead of desperate reaches like this. Oh, thats right, you have no valid argunment and need to once again, resort to spin and insults.
More desperate reaches and complete bullshit. What you said above means absolutely nothing. What does thinking that a vacuum system is perfect all of the time have to do with the problem and where did I ever say this???? While they don't have to be perfect to function, to claim the behavior from a leak is normal is just ignorant.
LOL, why is that??? I believe you may think that because they exceed you skill level. What makes it harder to diagnose than anything else? The check valve take all of about 10 seconds and the rest of it within a half an hour provided you know how to do it but for you, it might take all day so I can see why you treat it the way you do.
Hahahahahahahaha, you really are too funny. By definition, this is impossible.
What technical fact???? I have yet to see a single one. Your examples of old relics you own are not facts, just further examples of other problems using a very different system. You then come up with complete hogwash that a perfect system will cause as many problems as a defective one when even by definition, the word "perfect" means without flaw and therefore would be unable to have problems. Then you say because something is hard to fix, a results of the problem should be thought of as a normal condition. Yea, you have some killer technical facts here.
My credibility, with the crap you just spewed out here you should be the last one to talk about anyone's credibility.
I use a can of carberator cleaner to find vacuum leaks. With the engine running, spray the carb cleaner on the vacuum hoses. You can hear the engine slow when the carb cleaner enters the through the vacuum leak. I haven't had to do that to a fuel injected engine, but I don't think it would cause any harm.
Using the carb cleaner is fine, until you try it on the HVAC stuff under the dash.
application,
Where exactly is this "system wide" reservoir and exactly how does it work without a check valve?
Wow, you are really bright today. Did you have to look this one up?
Yea, they are referring to changing modes at high engine speeds, not steady state operation but you knew that, right?!
Hahahaha, complete BS. Only if the leak were severe enough but a minor leak would cause no erratic operation under high vacuum conditions.
Again, only with a MAJOR leak such as a broken line and even then, I doubt that the line that feeds the HVAC controls would be big enough to cause that level of a vacuum leak and if it were somehow that severe, the HVAC controlls wouldn't work at all. Then you keep forgetting that if the check-valve is the problem, there would be NO DETECTABLE symptoms as far as the engine was concerned. You really don't know shit about this, do you?
We do know better than you, both in our minds and in the minds of just about anyone that understands these systems with the crap you spewed out above.
Does carb cleaner cause a problem with the HVAC, or does it just make a mess inside the cab?
Carb cleaner tends to do a number on the soft plastic of the interior, plus its a bit difficult to get it to go where you want under the dash. add in the effort of getting to see what you are hitting, and the risk of getting a face full, and its a less than great idea.
The leaks these other guys are so hip to find tend to be found in the vacuum switch itself, making it hard to fix. Replacement is the best option, and the device can be fairly pricey. The reason I call it normal is because a vacuum switch rarely is "sealed" in the sense that most of us know. It'll only wear further, so the new one may be bad in weeks, or years, depending on a number of factors. hard acceleration will drop vacuum signal, and a leaky switch will allow it to dissapate completey in some cases.
So, is it normal, or is it a "gotta replace that because everything works perfectly in my truck, despite its age"?
Some people think its cool to look knowledgable. I figure its best to call it like it is... a vacuum system without a leak is NOT normal, its a rare bird.
However, your carb clean trick is tried and true for all things in the engine compartment, and is very effective there.
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