AC mode switch / vacuum troubleshooting

[Michael Babb]

So - after adding a new stereo to my car, the AC is a bit pissed off and will only blow air out in the foot well of the car. I added a double DIN radio, so disconnected this:
33314

to keep the center vents from opening . . .but do not think that would jack up the whole system? On initial start, I heard a vacuum hissing, and realized that the mode-switch had become disconnected from the vacuum hoses:
33315

I reconnected the hoses to the mode switch But I still get only foot-well air when I do any vent selection.

Something that I am missing, or recommendation on which hosts to check (and where they are) in case I disconnected another vacuum hose?

Thanks!

[mburshtain]

Take a look at the vacuum connections, they all have numbers and colors.
See attached.

[Michael Babb]

Take a look at the vacuum connections, they all have numbers and colors.
See attached.

Thanks! Have been looking at http://store.delorean.com/c-365-7-3-0-electricalmechanical-controls.aspx, but that does not go in to detail....and I am not sure where some of those hoses route to. Just printed out your attachment to use to check out the car again.

[mburshtain]

The most common issue is with the rubber seal of the mode switch.
You may need to order a mode control switch rebuild kit -

https://store.delorean.com/p-7759-mode-control-switch-rebuild-kit.aspx

[Michael Babb]

The most common issue is with the rubber seal of the mode switch.
You may need to order a mode control switch rebuild kit -

https://store.delorean.com/p-7759-mode-control-switch-rebuild-kit.aspx

was wondering about that as well, but since it worked perfectly before my radio work, I was thinking it was more likely something that I did under the dash....may pull the whole switch to check out the rubber seal itself.

[DMCMW Dave]

Did you do anything else to the vac lines? The vac line to the flap chamber still needs to be hooked up so you don't lose all the vacuum.

Keep in mind that when that flap is closed, it uncovers another hole that will bleed your air off to the windshield - as in defrost. Is your air perhaps coming out of the defrost vents rather than the sides?

You may need to physically block the two unused vents rather than securing the door closed.

[Michael Babb]

Thanks Dave - I did not intentionally do anything to any of the vacuum lines, but did have the whole interior out to work on the radio wiring and cables, so possible that I disconnected something unintentionally. the only thing that I changed with regards to the A/C was disconnecting the lever that opened and closed the center flap.

I checked with a tissue, and I do have some air coming out of the defrost vents. So, I have air on the windscreen and in the foot wells - and this does not change regardless of which mode-switch setting I use. Will try to dig in a bit more this weekend to check vacuum tubes.

[Michael Babb]

Fixed by magic! Got in the car last weekend to go to a St. Patrick's parade, already dreading having no vent air... And the mode selector worked perfectly... Go figure

[DMC5180]

Fixed by magic! Got in the car last weekend to go to a St. Patrick's parade, already dreading having no vent air... And the mode selector worked perfectly... Go figure

When you were doing these operational tests earlier did you have the engine running or just the key ON while playing with the control? If the latter you may have bleed of your vacuum reservoir supply. Your vent doors would be stationary in sort of a default mode. Floor Vents do not require a vacuum to be OPEN. vacuum is needed to OPEN them. Its a Default mode sort-a-speak and is the same (vacuum schematically) as putting the mode switch in the OFF position.

[Michael Babb]

Actually had it running when I was testing...

[DMC5180]

Actually had it running when I was testing...

Weird.

Oh and I meant vacuum is required to close the floor vents.

[Rich_NYS]

I'm working on my HVAC mode selectons, and have an issue that seems to only affect airflow to the footwell as well as the selections being a bit wonky.

I tested all modes, heat & cold. I'm looking for some help diagnosing, and help with understanding what to expect with each selection.


Max, Norm, and BiLevel: [HEAT setting] Center vent (low flow) and Driver's Door .....[COLD setting] Center Vents & Doors (high flow)

Vent: [HEAT setting] Center vent (low flow) and Driver's Door .....[COLD setting] Doors (High flow)

Heater: Only blows out the doors on HEAT or COLD setting

Defrost: [HEAT setting] Windshield (low flow) and Driver's Door .....[COLD setting] Doors


Observations:
-No air out the footwell vent on any selection
-Slight hiss on the Heater selection
-Defrost seems low-flow

Thanks!

[Rich]

There's a lot going on here.

First, the airflow/ducting velocity at each outlet isn't supposed to depend on whether you choose HEAT or COLD on the temp knob. That knob only controls the air temp so I can't figure out what's causing different flow situations with just a temperature adjustment. So I will set that aside for now.

Second, if you're getting low/zero flow to the floor ducts in HEAT mode and you hear a hissing sound in that mode or any mode you probably have a worn-out mode control switch. Simple to rebuild it if you take your time.
Houston and others have the parts. LINK: Example parts (https://store.delorean.com/p-7759-mode-control-switch-rebuild-kit.aspx)

Recommending you start with that. A bad mode switch can affect more than one of the duct control vacuum motors. A hiss from the A/C control area is almost certainly a sign of a bad/worn mode switch diaphragm.

Extra hint: Whenever you check your face level vent flow be sure both of the vent thumbwheels are in Open mode.



I'm working on my HVAC mode selectons, and have an issue that seems to only affect airflow to the footwell as well as the selections being a bit wonky.

I tested all modes, heat & cold. I'm looking for some help diagnosing, and help with understanding what to expect with each selection.

Max, Norm, and BiLevel: [HEAT setting] Center vent (low flow) and Driver's Door .....[COLD setting] Center Vents & Doors (high flow)
Vent: [HEAT setting] Center vent (low flow) and Driver's Door .....[COLD setting] Doors (High flow)
Heater: Only blows out the doors on HEAT or COLD setting
Defrost: [HEAT setting] Windshield (low flow) and Driver's Door .....[COLD setting] Doors

Observations:
-No air out the footwell vent on any selection
-Slight hiss on the Heater selection
-Defrost seems low-flow

[Ron]

Refer to the .PDF in post #2. Disconnect each line going to the switch and confirm they will hold vacuum, except #1 (black=supply). A leak involving port #5 (black/Red) could cause a lot of what you are reporting. So could the flap it operates being stuck. If all OK, use the chart at the bottom of the PDF to check switch operation using a cigar etc. (Or see Lou.)

[Rich_NYS]

Great help, thanks guys.

I made sure the center vents are open and shined a light inside to confirm the flap was opening & closing.

Saturday I'll do as Ron suggested, and will also prepare to replace the switch diaphragm Rich mentioned.

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[Rich_NYS]

I have a lot of things apart; working on my wiper issue, and HVAC.

I checked all the hoses, they all appear to hold vacuum, and I can hear most of the actuators working (others I can hear/feel changes in the airflow when the selector is changed.

Tomorrow I'll go further with the testing, but I also noticed the hissing noise is fairly significant (albeit brief) when I turn off the car, so that seems to be indicating the switch as Rich mentioned.

[Rich_NYS]

I'm pretty sure it's the mode switch, I have it out where I can manipulate it and if I squeeze it to where it doesn't hiss it seems to function properly.

I'll rebuild it and see how it goes.

[David T]

If the mode switch hisses it is worn out. Even if you can get it to be quiet, it can still be leaking, it just isn't making any noise. Most of the time, if you have a problem with the actuators and the mode switch is hard to turn or is hissing, if you rebuild it, all of the problems are fixed. The other common problem is a vacuum hose that got disconnected. Just be careful to put the wires and hoses back correctly. Make notes or take pictures. Be gentile with the plastic parts. They are brittle and can break easily. On one car I fixed the vacuum feed hose was pinched under a console support but if your mode switch is hissing you've got vacuum.

[Rich_NYS]

Thanks David, I'm going to rebuild the switch this week and will post results.

[Rich_NYS]

Rebuilt it today; I think it's better (everything seems to work,) but now whistles on the heat setting and hisses worse than before. WTH.

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[SS Spoiler]

Took mine apart, smeared Vaseline, workn'
good 32 years now.....

[Rich_NYS]

Took mine apart, smeared Vaseline, workn'
good 32 years now.....Did you put a lot on it?

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[Ron]

I didn't think it would be a big deal if some got into the tubes and used a liberal amount. Lasted 5 years when I sold it...

Is everything still apart enough that you can tell it's the switch hissing for sure?

[Rich_NYS]

~snip~
Is everything still apart enough that you can tell it's the switch hissing for sure?Yes. I can hold it in my hand while the car is running and change the noise by covering different parts of the switch. I took it apart a few more times to add vaseline, then reinstalled the original diaphragm for comparison.

FWIW, my switch has one round hole, three oblong holes. The original diaphragm matches. The replacement has one large round nub, three small round nubs. Steve said he doesn't think the holes on his switch are oblong.

[Ron]

IIRC, on all of them I have seen there was one nub larger than the others for orientation. I haven't needed to install one for a few years now though.

...now that I think about it, I remember two that were glued on and thinking the nubs must of broke....

I wouldn't think it would leak from the sides (ie not through a port) because it was not aligned (rotated). Any chance the electrical portion got yours too hot and warped/damaged the plastic?

[Rich_NYS]

~snip~ Any chance the electrical portion got yours too hot and warped/damaged the plastic?

Sounds plausible.

I think there must be something wrong with my switch.

[David T]

It could be cracked. On the earlier cars the hoses are directly attached to the switch. On later cars they attach to a large rubber plug and the plug fits to the switch so you don't have to remove each hose individually, you take the whole plug off. If your hoses are hard and brittle they could be leaking where they connect to the switch. Take teh switch apart and inspect it closely. There are nubs or bumps so you don't assemble it incorrectly. You should not use a petroleum based lubricant like Vasoline, it will eventually cause the rubber diaphragm to break down. There are products out there that are specifically made to be used with rubber.

[Rich]

+1, particularly about NO Vaseline on the seal.

Use a silicone grease, same as you would on car door weatherstripping or on an o-ring. Vaseline petroleum jelly will attack some kinds of elastomers/rubber so it's best not to use it on the mode switch seal.

A thin wipe of silicone grease with a clean cloth onto the face of the seal will do.


It could be cracked. On the earlier cars the hoses are directly attached to the switch. On later cars they attach to a large rubber plug and the plug fits to the switch so you don't have to remove each hose individually, you take the whole plug off. If your hoses are hard and brittle they could be leaking where they connect to the switch. Take the switch apart and inspect it closely. There are nubs or bumps so you don't assemble it incorrectly. You should not use a petroleum based lubricant like Vasoline, it will eventually cause the rubber diaphragm to break down. There are products out there that are specifically made to be used with rubber.

[Rich_NYS]

Half say use vaseline, half say don't....I'm going to use Vaseline on one half of it, silicone on the other half.

I returned everything to its original config (with the stock diaphragm) and used an incense stick my hippie voodoo-child wife gave me. I can see the smoke getting sucked in at the edge of the diaphragm, but nowhere else. All the hoses and the adapter are very flexible and rubbery.

I'll replace the diaphragm with the new one and test again to see if I get the same result.

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[ritztoys]

Years ago my mode switch failed(diaphragm had slipped out of position on the moving part of this IIRC)

I found only one 'nub' holding everything kinda in proper place. I removed the rubber part. thoroughly cleaned and re-installed in proper place w/superglue.

I polished the metal part to a shiny surface and coated the rubber part with 'baby powder', still working fine for over 25 years!

[Ron]

Half say use vaseline, half say don't....I'm going to use Vaseline on one half of it, silicone on the other half.LOL
It all depends on the rubber (natural, synthetic, etc). If its viton like the PPR o-ring, no problem even with gasoline.
Play it safe and use the silicone grease.

[Rich_NYS]

~snip~

I polished the metal part to a shiny surface and coated the rubber part with 'baby powder', still working fine for over 25 years!

I'm going to try this...thanks for the tip!


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[Rich_NYS]

So far nothing stops the hiss. New diaphragm hisses & whistles, cleaning & polishing seemed to help a little.

FWIW, I don't think the new diaphragm is a proper fit. The old one had raised "keys" the same size & shape as the switch....the new one has "keys," but three are not the same size & shape.

I tested with smoke and can see it getting sucked into the edge of the diaphragm.

I put everything back together....aggravation for a different day.

Probably sell the new diaphragm.

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[Ron]

Maybe try putting a very thin washer under the two plastic prongs to shim it tighter. You can notch the hole to shape with a square/box file.
If you're lucky, you can locate a horseshoe clip to fit. (It's brittle -- I'd try aligning it all up and press the plastic through all at once, instead of slipping it under the plastic prongs. Wash the back side of the diaphragm (for grip) and lots of silicone on the maze.)

[David T]

You should not be having so much trouble with this. Maybe somehow you don't have the right switch or someone messed up the parts. One thing you could do is send the switch out to a Delorean vendor and ask them to assemble it for you. They would immediately see if something is not right knowing exactly what it should look like.

[Rich_NYS]

Maybe try putting a very thin washer under the two plastic prongs to shim it tighter. You can notch the hole to shape with a square/box file.
If you're lucky, you can locate a horseshoe clip to fit. (It's brittle -- I'd try aligning it all up and press the plastic through all at once, instead of slipping it under the plastic prongs. Wash the back side of the diaphragm (for grip) and lots of silicone on the maze.)

I was thinking I needed it tighter, and tried "elongating" the spring early on. I'll try the washer idea on the next go-around.


You should not be having so much trouble with this. Maybe somehow you don't have the right switch or someone messed up the parts. One thing you could do is send the switch out to a Delorean vendor and ask them to assemble it for you. They would immediately see if something is not right knowing exactly what it should look like.

I agree, it's a pretty simple task and I shouldn't be having such a hassle. I like the idea of sending it to a vendor for a more experienced set of eyes (and better part-swapping resources.) I don't need help assembling it, though....every part of it is keyed, it seems pretty foolproof to reassemble.

I have an odd thought/silly question: is it possible that too much vacuum could be causing the issue? I put a gauge on my manifold, it's at the high end of the scale/

[David T]

The motor can't produce "too much vacuum". Maybe take a ride to PJ Grady with it.

[Rich_NYS]

The motor can't produce "too much vacuum". Maybe take a ride to PJ Grady with it.Lol....not going to drive 200 miles for a HVAC switch. Ain't nobody got time for that!

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[David T]

Then either have him do other stuff too or just mail him the switch. I would call first.Or wait till you have other business in the area nearby.

[Rich_NYS]

Today I picked up my latest DeLorean purchase. The owner had a small parts stash, and coincidentally it contained one of these:
https://uploads.tapatalk-cdn.com/20191126/f146a0b6fabf4d8731a4cc218eb35b72.jpg

[JohnZ]

I'm sorry to refresh this thread, but I'm about to replace the rubber diaphragm as well!

My only question is: how in the world do you remove the switch without taking the console out? If I put my head on the carpet floor in the passenger side and look towards the inner part where the vacuum hoses are supposed to be... I see nothing but a mess of cables! I can't reach the switch from behind, let alone remove it and put it back properly!

So: are there other parts to remove to clear the visual up? Because I think that removing the center console may be paramount to perform this job...

:)

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[82DMC12]

I'm sorry to refresh this thread, but I'm about to replace the rubber diaphragm as well!

My only question is: how in the world do you remove the switch without taking the console out? If I put my head on the carpet floor in the passenger side and look towards the inner part where the vacuum hoses are supposed to be... I see nothing but a mess of cables! I can't reach the switch from behind, let alone remove it and put it back properly!

So: are there other parts to remove to clear the visual up? Because I think that removing the center console may be paramount to perform this job...

:)

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It's been said you can remove the mode switch without removing the console but I don't feel like fishing around back there and probably jacking up something else. Just take the console out. Not that hard.

[JohnZ]

Ok thanks Andy! I've been removing the center console a couple of times before, it's just tedious but I feel like I want to do it, because I don't want to screw things up! :)

I wonder how people managed to do it without removing the console though..... It's just a mess in there

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[mike123]

It was recommended to me to go at it from the driver's side, and I did find it easier to access the mode switch and get it clear of the rat's nest of wires/hoses from that side.

However, the length of the hoses did not allow me to really pull it out of the area, I could just get it to the edge of the mess, if that makes sense. And I chickened out because I didn't want to risk pulling a hose too far and disconnecting it somewhere else, or pulling off the switch and dropping or losing a hose back in the rat's nest to never be found again. So I have a replacement mode switch in my basement and still have a slightly hissing (but working) original switch in my car :-)