A/C switches vents on its own

[mark_gober]

Hey everyone,

I've looked through the forums and I can't find anything on this. (Although I SWEAR that I've seen it...maybe I am just not searching with the correct terms) Here's my problem.

I have a 2000 Windstar w/ the 3.8l. The A/C works fine, with one very small exception. When the engine is under a moderate strain, such as climbing a small hill on the freeway, the a/c vents automatically switch to the defrost. If I release the gas pedal, they pretty quickly switch back to vents. Thats about the only time I get this problem, but man is it annoying.

My brother has a 2003 that did the exact same thing. His solution involved removing the radio and reaching in and wiring the vacuum solenoid into the vent position. Obviously, it will work, but then you're tied to vent only operation. I'd like to just fix the stinking problem and be done with it. I've checked for obvious vacuum leaks and don't see any.

Does anyone have experience with this problem and can you steer me in the right direction. I'm just curious as to why you'd have the problem under moderate strain, but not heavy acceleration or idle. Look forward to your feedback.

Mark

[olopezm]

Hello Mark

That happens because of a vacuum leak, if the system does not detects enough vacuum it will revert back to defrost mode, that way "you might be freezing but at least you can see in the winter" as someone said before in the forum LOL. When you're going uphill or as you step on the pedal the vacuum at the engine decreases and the VACUUM RESERVOIR provides the stored vacuum needed for the AC system.

Now onto the vacuum leak, I have the same problem with mine, I already found where the leak is, but since I haven't had enough time I haven't found the exact place where I should connect the loose hose. It is located at the back of the plastic intake manifold it's a red colored hose you can easily trace it if you put your hand at the back of the manifold passenger's side it has a small check valve (white and black colored) which some other users have had problems with. This same hose goes from the intake manifold to the check valve which has a rubber tee and from there it connects to the firewall and to the vacuum reservoir under the windshield cowl, this is the point where the hose on mine was disconnected but I still need to take the cowl apart in order to find the spot where it should be connected.

If you have the same problem as me and you decide to take the cowl off I would really appreciate if you could take and upload some pictures, other than that you won't need to take anything apart and you can easily fix your problem.

Best regards,

Oscar.

[olopezm]

I don't know if you still have the problem but I fixed mine last week and I would like to post some pictures in case you or someone else need them:


This is the hose that gets disconnected from the back passenger side of the intake manifold.


This is where that hose should be connected to.


This is the other end of the same hose, it has a check valve on it and this side is connected to the vacuum reservoir and into the firewall to the dashboard to control the A/C system.


This image is just to show the location of the vacuum reservoir, you'll have to remove the cowl in order to see it properly, if you don't you can still reach the reservoir but it will be a bit hard since you don't have much space.


Here's the vacuum reservoir and the hoses viewed from another perspective.

Hope this information helps.

Best regards,

Oscar.

[azharj]

Dear olopezm
Thanks for nice pictures. I located the vacume check valve, checked vacume reservoir and all the pipes. Vacume check valve seemed to be defective and so replaced. As a further savegaurd I positioned the valve vertically instead horrizontally.
I will mention that in hot days after drive of 150 miles sometimes my windstar 2000 is not accelerate or does not maintain speed particularly at up-slopes some times but at night it is normal. (probably fuel pump problem??) The problem of A/C withiching to defrost improved, that previously I had to off the cruiseor reduce the speed to bring the switch normal. However, it still persists. Can u or any one guide me what to do next?

[olopezm]

Hello azharj,

I'm glad you found the information somehow useful.

I think your first problem is the installation of the check valve, it should have been installed the same way the older one was. It is designed to provide vaccuum from the reservoir to the firewall (the dashboard) and to keep it from going back to the engine. If you installed the valve in a different position you must still be loosing some vacuum. I would install it horizontally again.

The other problem I think might be related to the MAF sensor if it happens only when hot; you can try disconnecting the harness going into the MAF and running the engine like that (it may turn off the first times, just start it again); it is located after the air filter inside the big plastic tube and has a rounded connector attached close to the battery (that's the connector you need to disconnect). If you find out your windstar runs better with it disconnected when hot then the next step would be to give it a good clean with some electric contact cleaner, MAF cleaner (if available) or some other non-oily and none residue cleaner. Failure to use only these types of cleaner will damage the sensor (if it's not already).

Regards,

Oscar.

[azharj]

Thanks Olopezm,
Can I use wd 40 to clean MAF because cleaners are not available here?
But I will do this after changing IAC today. Best regards AzharJ

[olopezm]

Don't use wd-40 to clean it, if it's only dirty it is very likely it will be damaged because of it's oily nature. Do you have access to any electronics shop? These should have at least electric contact cleaner, which evaporates quickly and leaves no residue.

Whatever you do, do not touch the small wires on the MAF, these can break with the slightest pressure.

Oscar.

[azharj]

Dear Olopezam
I am highly thankful to u for the information.
with best regards
AzharJ

[olopezm]

You are welcome!

However I suspect you haven´t found any good advise. I would suggest you to start a new thread where you mention all of the problems your windstar has; I´m pretty sure you will get MUCH MORE help by doing so.

Regards,

Oscar.

[azharj]

Dear Olopezm,
Whatever still I beleive all it is good advice from all forum members. I will like to ask that the red hose commin from manifold is common with another hose may be black or grey; where is this secon Hose going.
best wishes,
AzharJ

[olopezm]

I can't remember exactly but I think that the other hose goes to the EGR valve, that could give you rough idling now that you mention it, make sure to trace the entire hose at the back of the intake and feel for any cracks.

The EGR valve is a round plate connected by a steel pipe to the front exhaust manifold (the valve looks like a UFO) it sits right at the front of the engine, right below of the throttle body. Inspect that hose.

You can see a picture (tenth picture) from the back of the engine in this page:
http://leckemby.net/windstar/windstar01.html

Regards,

Oscar.

[azharj]

Dear,
This white tube is in common with red on intake manifold end. The red tube goes to vacuum reservoir and the white tube goes to vapor canister purge part of the feul vapor system. Leckmby very good page but does not shows the white tube or whereit is going.
Best wishes,
AzharJ

[azharj]

Dear Olopezm
I fixed the issue of vent deflection to the defrost position. I made two amendments:
1.) fixed check valve vertically see diagram No. 1.
2.) repositioned the whole check valve and vacuum reservoir assembly inside, under the dashboard
I fixed the valve vertically because the air can travel from the white side to the black side only. In the cylindrical part which is between the two white and one black tubes (marked red), diagram 2 &3there is small thin circular plastic disk like membrane. This plastic membrane closes the way back to white tubes. If the valve is vertical, the sheet will be horizontal, thus closing the white tubes by its weight, all the time.
One of the white tubes is connected to the vacuum canister. From the other white tubr, a black hose goes to the control knob, from which different hoses go to the different actuators. See the connection diagram (NO. 4) of the hoses. Leak can occur at any of the connection points between manifold and the red hose, hoses and check valve, vacuum canister, control knob, and actuators; and the hoses, check valve, vacuum canister and actuators themselves. However, the most probable site of leak is on the engine side, where the changes in the temperature due to engine heat and cold external temperature can damage the plastic parts by making them inflexible.
I removed the hose, the canister and check valve, which I had replaced recently, plugged the open ends, dipped all of them in a bucket of water and applied pressure to one end. I came to know that all the joints and vacuum canister were leaky, even though I had secured all the joints with silicon and wires. There was a small phalange of residual plastic material along the whole length of the tubes of the valve. This phalange was preventing airtight fitting of hoses with the check valve. I repaired the leak of the vacuum canister and filed it to smoothen the tubes of the check valve. I took a long new hose to connect it to the manifold on the one end and firmly connected the other end to the black hose, which is connecting the vacuum canister to the control knob, to pull the new hose inside. I could find much place behind on the glove box just on the passenger side of the central console and fixed the check valve and vacuum canister on the new place; so that any future service is easy. Other advantage was that it gave much space to replace the metallic heater hose. Alternatively, creating 15-inch vacuum in all hoses, check valve, canister control knob and actuators, and a fall in vacuum by 1 inch per min will detect leaky part.
see Link: http://www.automotiveforums.com/vbul...02#post6921202
http://www.automotiveforums.com/vbul....php?t=1074091
http://www.automotiveforums.com/vbul....php?t=1052185
AzharJ

[olopezm]

Wow!

That's a great troubleshooting Azharj; congratulations on all your hard work.

I'm pretty sure your information will help somebody else with a similar problem,

All the best to you my friend,

Oscar.