Heater modification project

[Tomcio]

Hello everyone,
I want to share my project with everyone that might be interested in improving the heating in the DeLorean. When I used to live in Florida I didn't care much about the heater as I used the A/C pretty much all year round. I got that taken care of, flushed the lines, replaced the oil, replaced all o-rings, recharged the system and it was cold. And when I say cold I mean 45 degrees F at the center vents in Florida heat. Plenty of nice and cool airflow. All was great. Then I moved to a much cooler climate and started using the heater more often. It became very apparent that there is something wrong with the heating. It was ok when directed down to the floor or up to the windshield. When switched to center vents there was almost no air coming out. Sound familiar?? I thought something was broken, a flap didn't work or something was blocking the path. Now that I've taken the A/C box apart I had a good chance to investigate what the problem was. As it turns out it is just very poor design and I mean VERY poor. Something has to be done...

There are two flaps that control the airflow to the center/door vents. When closed all air is directed to the floor or the dashboard.
This is what it looks like with the temperature flap removed and both center vent flaps closed looking from where the air enters the distribution chamber - notice the heater core in the upper part of the picture:
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In this configuration the air comes in from where the camera is and depending on the temperature flap goes straight in or up and through the heater core.

Trouble starts when you want some warm air through the center vents. In the bi-level position of the mode switch one flap opens and this is what you get:
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Half of the flow bounces off the flap and is directed to the center/door vents and half goes through the remaining opening and flows down to the floor.

If you want all of the air coming out the center/door vents both flaps open and you get this:
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With temperature setting at full cold all air goes straight, bounces off the flaps and is directed to the center vents.

If you set it to full hot all the air goes up and through the heater core and down through the little space left above the open flaps:
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There's a gap of about 8mm or less than 1/3 of an inch between the flaps and the heater core.

You can see in the picture below that only about 25mm or 1 inch of the heater core remains "open":
28544
No wonder there's almost no air coming out of the center/door vents when temperature is set to hot.

The lines on the flaps you see in the pictures above were drawn after carefully measuring the required opening. I approached the problem with an angle grinder and a 1mm cut-off wheel and just a few minutes later this is what I got:
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As you can see now I will get full and unrestricted airflow coming from the heater core. That should make a huge difference because the opening will now be 40mm (1.6") instead of the original 8mm (0.3").
This, of course, creates a problem... When closed the flaps will no longer seal the center/door vents (looking from the outside):
28546

This will be fixed in a second step. The sections that were cut off will be attached with a hinge. A simple lever will be installed so the little sections will allow the flaps to seal off the center vents but will swing open when the flaps are raised.
This is just my first post on this subject. I will post further details and pictures as work progresses. I need to get some nice small hinges to make it work now.
Stay tuned if you're interested. I should post an update within a few days...
Upon completing this modification I will post some before and after comparison of the amount of airflow.

[NightFlyer]

Heater works great in my car without any mods - it will sweat you out in freezing temps.

[Tomcio]

Well, it worked in my car too and the air coming out of the vents was very hot. There was just very little of it. It was fine when set to windshield, floor or bi-level. When set to center there was very little flow. Set your mode switch so you have air coming out of your center and door vents, set fan to 3 or 4. Then move the temperature knob from full cold to full hot and see if the airflow remains the same. That is what I'm trying to fix. I had to take everything apart anyway (all flaps were really rusty and all foam had disintegrated) so I figured that I'll do this while I'm in there.

[Lightning]

I currently have my system apart while doing a restore of 5096. Let me know what you come up with as I'm curious if I want to do the mod while I have the box out.

[NightFlyer]

Well, it worked in my car too and the air coming out of the vents was very hot. There was just very little of it. It was fine when set to windshield, floor or bi-level. When set to center there was very little flow. Set your mode switch so you have air coming out of your center and door vents, set fan to 3 or 4. Then move the temperature knob from full cold to full hot and see if the airflow remains the same. That is what I'm trying to fix. I had to take everything apart anyway (all flaps were really rusty and all foam had disintegrated) so I figured that I'll do this while I'm in there.

Yeah, airflow remains the same - good and strong.

BTW - I have the mode switch set to vent with the temp control turned full hot.

Maybe I just lucked out :biggrin:

[Tomcio]

Yeah, airflow remains the same - good and strong.

BTW - I have the mode switch set to vent with the temp control turned full hot.

Maybe I just lucked out :biggrin:

Apparently your flap system must be different than mine. Was there a change in the design of the A/C box? I've seen the same effect of dropping airflow when moving from cold to hot on numerous cars including vins 6298, 6149, 3633 and 2418. In all those cases the flow drops significantly when moving the temp knob. I would say that the amount of cold air is at least four times the hot flow.
Your VIN is earlier than mine. Maybe they changed the design of the box during the production. That would be very interesting. It would be great to be able to see and compare the insides of the two boxes to see where the difference comes from.
Anyway... I'm continuing with my project and expanding it as I'm going forward. I'm thinking about replacing the vacuum actuators with electronic servos and replacing the mode switch with something different. One thing will be changed for sure. The heater core valve that sits in the engine compartment will be replaced with a proportional valve that will be controlled by the temperature knob. In the current setup the heater core is always hot except for two settings - OFF and MAX A/C. As a result the entire A/C box gets fairly hot and I get warm air out of the vents even when set to full cold. There were days when I had to use the A/C even though it wasn't hot outside.
This is fun ;)

[Bitsyncmaster]

Anyway... I'm continuing with my project and expanding it as I'm going forward. I'm thinking about replacing the vacuum actuators with electronic servos and replacing the mode switch with something different. One thing will be changed for sure. The heater core valve that sits in the engine compartment will be replaced with a proportional valve that will be controlled by the temperature knob. In the current setup the heater core is always hot except for two settings - OFF and MAX A/C. As a result the entire A/C box gets fairly hot and I get warm air out of the vents even when set to full cold. There were days when I had to use the A/C even though it wasn't hot outside.
This is fun ;)

I also thought about using electric servos. But will be doing what your doing changing the heater valve with one that turns on or off with the temp knob. My plan is to just use a micro switch on the temp knob being set to full cold. I have an electrical valve but it's not a proportional valve, just full open or full closed.

[dmc6960]

I can vouch for the airflow dramatically going down when switching the temp over to hot. Though I always attributed it to the smaller heater core and the added resistance of going though two coils. My comparison has always been at the center vents. I never did a full sweep on the floor vents, will have to give that a try. I've never felt the car didn't have enough heat though as I always have it on the floor vents in heat mode. I get cold feet easily so that never changes.

[NightFlyer]

Apparently your flap system must be different than mine. Was there a change in the design of the A/C box? I've seen the same effect of dropping airflow when moving from cold to hot on numerous cars including vins 6298, 6149, 3633 and 2418. In all those cases the flow drops significantly when moving the temp knob. I would say that the amount of cold air is at least four times the hot flow.
Your VIN is earlier than mine. Maybe they changed the design of the box during the production. That would be very interesting. It would be great to be able to see and compare the insides of the two boxes to see where the difference comes from.
Anyway... I'm continuing with my project and expanding it as I'm going forward. I'm thinking about replacing the vacuum actuators with electronic servos and replacing the mode switch with something different. One thing will be changed for sure. The heater core valve that sits in the engine compartment will be replaced with a proportional valve that will be controlled by the temperature knob. In the current setup the heater core is always hot except for two settings - OFF and MAX A/C. As a result the entire A/C box gets fairly hot and I get warm air out of the vents even when set to full cold. There were days when I had to use the A/C even though it wasn't hot outside.
This is fun ;)

Never had my box out, so I couldn't tell you. Next time we all get together for a show or something, I'll have to demonstrate the operation of my system and compare to someone else's. Just checked it again this morning, and the air flow feels the same to me between both hot and cold temp control adjustments.

Are you sure that the control valve is closed when the mode switch is set to 'off?' I thought the vacuum to pull the valve closed was only activated when the mode switch was set to 'Max A/C.' I personally never experimented to know for sure - I've only heard it repeated many times by those supposedly 'in the know' that the hot water (control) valve was only pulled closed when the mode switch was set to 'Max A/C,' thus I'm very curious about this now.

[jmettee]

Yeah, airflow remains the same - good and strong.

BTW - I have the mode switch set to vent with the temp control turned full hot.

Maybe I just lucked out :biggrin:

Maybe I lucked out too. Mine seems to work fine & I've driving mine in freezing temps a number of times. Never had a complaint about the heating capability of my car in temp or airflow. Maybe there is something different among the various builds.

[Tomcio]

Are you sure that the control valve is closed when the mode switch is set to 'off?' I thought the vacuum to pull the valve closed was only activated when the mode switch was set to 'Max A/C.' I personally never experimented to know for sure - I've only heard it repeated many times by those supposedly 'in the know' that the hot water (control) valve was only pulled closed when the mode switch was set to 'Max A/C,' thus I'm very curious about this now.

You're right. I checked the operation of the mode switch and it is as you said. The heater valve is always open and closes ONLY when set to MAX A/C. That has to change as I like to drive my car with no A/C when it isn't too hot outside. With the whole dash getting so hot from the heater core I have to use the A/C even on relatively cool days.

As for the flap system, here's step two of the project:

The small section of both flaps were reattached. I found some nice stainless steel hinges that will work.
Here's a view from the outside with both flaps closed (floor or windshield open):
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It's slightly out of line because I didn't assemble the whole setup yet. It was just a test fit.
As you can see the opening leading to the center vents will now be closed off and all air will be directed to floor or windshield vents.

When the center vent flaps open, the little flaps swing open to allow full airflow from the heater core:
One little flap is open and one is closed to show the difference between the two.
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Next step is to install some simple linkage that will control the little flaps.

Stay tuned, I'll post some more pictures when I complete the linkage setup.

[NightFlyer]

Looking very beefy / heavy duty - I like it :thumbup:

[Tomcio]

Looking very beefy / heavy duty - I like it :thumbup:

Yeah, I didn't want some cheap flimsy hinges because I was afraid they might rattle or squeak. Once the box is all assembled and installed it would be very difficult to do anything about it.

[Tomcio]

For all those interested in this modification...
Not much has been done yet. As it turns out the simple linkage to open the little flaps turns out to be not so simple. I'm having real difficulty with finding a solution to this problem. I've spent hours trying different configurations and I can't seem to find a good solution. There's always a problem of the flaps either not opening or not closing fully. At this moment I'm playing with an idea of connecting a cable that will work together with the temperature flap. This would be the best solution to the problem because it would allow me to keep the heater core blocked off when cold air is needed while allowing full flow through the heater core. Hmmm.... I'll let you know when I find a good solution to this problem.

[DMC5180]

The heater valve is always open and closes ONLY when set to MAX A/C. That has to change as I like to drive my car with no A/C when it isn't too hot outside. With the whole dash getting so hot from the heater core I have to use the A/C even on relatively cool days.


Tom,

Were you getting a hot foot at the gas pedal?

Was the foam around the heater core tubes loose from the housing?

This is a common problem and will give you the feeling your heat is on in the summer because the air is leaking out the gap in the housing.

When I had my heater/a/c unit out back in 2010 I fixed the issue by fabricating a 2 piece sheet metal closing plate to completely seal off the the long slots in the housing.

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[Tomcio]

Tom,

Were you getting a hot foot at the gas pedal?

Was the foam around the heater core tubes loose from the housing?

This is a common problem and will give you the feeling your heat is on in the summer because the air is leaking out the gap in the housing.


That is a very nice fix. I like that!
On my car the foam was not loose... it was gone. There were just little pieces that looked like dust sprinkled on a layer of old glue. Since I was aware of this problem I fixed that a few years back while still in Florida. The real problem is the design of this system. The heater core gets to the engine temperature and everything around it gets hot as well. If the weather is nice, lets say 70 degrees and I drive around with mode switch on Vent and fan on speed 1 the entire A/C box will get hot. After a while I start getting warm air out of the center vents because of all that heat in the A/C box. The longer the drive the warmer the air from the vents. As some point I have to switch the A/C on because it's just getting too hot.
I did some experimenting while my car was still in one piece and I connected the heater core valve to constant vacuum in the engine compartment. The difference was huge - no more heat, no warm air, no hot dash. I could drive all day long on vent and fan on 1 and I didn't get hot.
A friend of mine is currently working on a digital controller for me. The idea is to use an Arduino controller that will take care of all the flaps in the air box. The heater core valve will be driven by a stepper motor and this is how I will change the temperature. This will be a bypass valve and the water will circulate back to the engine or through the heater core.
If this works out I will get rid of the vacuum actuators and I will be able to finally get rid of that mode switch. I really don't like that thing.

Thanks!

[Josh]

That is a very nice fix. I like that!
On my car the foam was not loose... it was gone. There were just little pieces that looked like dust sprinkled on a layer of old glue. Since I was aware of this problem I fixed that a few years back while still in Florida. The real problem is the design of this system. The heater core gets to the engine temperature and everything around it gets hot as well. If the weather is nice, lets say 70 degrees and I drive around with mode switch on Vent and fan on speed 1 the entire A/C box will get hot. After a while I start getting warm air out of the center vents because of all that heat in the A/C box. The longer the drive the warmer the air from the vents. As some point I have to switch the A/C on because it's just getting too hot.
I did some experimenting while my car was still in one piece and I connected the heater core valve to constant vacuum in the engine compartment. The difference was huge - no more heat, no warm air, no hot dash. I could drive all day long on vent and fan on 1 and I didn't get hot.
A friend of mine is currently working on a digital controller for me. The idea is to use an Arduino controller that will take care of all the flaps in the air box. The heater core valve will be driven by a stepper motor and this is how I will change the temperature. This will be a bypass valve and the water will circulate back to the engine or through the heater core.
If this works out I will get rid of the vacuum actuators and I will be able to finally get rid of that mode switch. I really don't like that thing.

Thanks!

that would be wonderful to do away with the vacuum operated flaps. Subscribed!

[Tomcio]

[...]
A friend of mine is currently working on a digital controller for me. The idea is to use an Arduino controller that will take care of all the flaps in the air box. The heater core valve will be driven by a stepper motor and this is how I will change the temperature.[...]

Well... this project is starting to appear as yet another failed attempt. :(
My friend who claimed to be a great programmer and an engineer and who said that programming Arduino is simple, is only good at releasing magic smoke. Apparently he has no idea how to make it all work and no idea how to program the Arduino. So far he managed to release the magic smoke from the stepper motor controller, voltage regulator, OLED screen and the main chip. The plan was to use a small 1" OLED screen to display the vent mode and another one to display the fan speed. He also managed to burn himself on the stepper motor because it got so hot in the process.
So, until I find someone who can actually write the software I have to go back to the stupid vacuum actuators and that pos mode switch. I have to put the dash back together now and I don't feel like spending any more money so this idiot can keep burning stuff up. I've worked with electronics for quite some time but I know nothing about programming the Arduino and have no time to start learning now.
So, it's back to the OEM stuff... at least for now.
:sad30:

[Bitsyncmaster]

I have been planning to replace the heater shut off vacuum valve with an electric (open/closed) "servo" valve.

I did produce a few circuit boards with a micro that drives an actuator that has two wires and it reverses power and ground to make it work. I'm also using that board to run my battery cut off latching relay which is why I went to the expense of making a circuit board.

I don't plan to replace the other vacuum valves. What would that gain? Doing the heater shut off unit will let me keep the heat shut off so the AC runs better when not set to MAX AC. If I need to defog the windows, I will turn the heat knob up and that will have a switch to open the heat valve.

[Shep]

Well... this project is starting to appear as yet another failed attempt. :(
My friend who claimed to be a great programmer and an engineer and who said that programming Arduino is simple, is only good at releasing magic smoke. Apparently he has no idea how to make it all work and no idea how to program the Arduino. So far he managed to release the magic smoke from the stepper motor controller, voltage regulator, OLED screen and the main chip. The plan was to use a small 1" OLED screen to display the vent mode and another one to display the fan speed. He also managed to burn himself on the stepper motor because it got so hot in the process.
So, until I find someone who can actually write the software I have to go back to the stupid vacuum actuators and that pos mode switch. I have to put the dash back together now and I don't feel like spending any more money so this idiot can keep burning stuff up. I've worked with electronics for quite some time but I know nothing about programming the Arduino and have no time to start learning now.
So, it's back to the OEM stuff... at least for now.
:sad30:Tom, either you're talking about me (and I suspect you're not since I have only gotten magic smoke out of a voltage regulator and a decade counter -- how does one burn out an OLED screen exactly??? :tongue: ) or you need me. Send me an email, we can go over the specifics. Consider yourself back in business! :biggrin:

[Tomcio]

I don't plan to replace the other vacuum valves. What would that gain? Doing the heater shut off unit will let me keep the heat shut off so the AC runs better when not set to MAX AC.
Replacing all the actuators and the heater control valve will let me remove the mode switch. I really don't like that switch. It will also allow the removal of temperature knob and fan speed knob as everything will become software controlled. All this along with a few temperature sensors would let me add one great function that I really love in my other car - AUTO function. You set the temperature and that's it! That's what I wanted.


Tom, either you're talking about me (and I suspect you're not since I have only gotten magic smoke out of a voltage regulator and a decade counter -- how does one burn out an OLED screen exactly??? :tongue: ) or you need me. Send me an email, we can go over the specifics. Consider yourself back in business! :biggrin:
No Shep, I wasn't talking about you. I was talking about my friend over here. I bought some stuff and he was absolutely sure he can make it happen. All he did was burn everything up.
I have no idea how he burned out that OLED but I'm pretty sure that you can do it by using a wrong power supply or just by making some wrong connections. I don't know, I wasn't there. He just called me one day and said that he heard a pop and now the screen doesn't come on anymore.
I'm still waiting for your PWM code, I don't want to bother you with this stuff.

[Shep]

No Shep, I wasn't talking about you. I was talking about my friend over here. I bought some stuff and he was absolutely sure he can make it happen. All he did was burn everything up.
I have no idea how he burned out that OLED but I'm pretty sure that you can do it by using a wrong power supply or just by making some wrong connections. I don't know, I wasn't there. He just called me one day and said that he heard a pop and now the screen doesn't come on anymore.
I'm still waiting for your PWM code, I don't want to bother you with this stuff.I didn't think you were, but my fiancee asked (she was sitting next to me at the time), so I thought I'd make a joke of it :wink:

I actually completely slipped on the PWM code -- I've had time to do it, but it totally escaped my mind. Will get all that squared away tonight for you :thumbup:

[Shep]

I actually completely slipped on the PWM code -- I've had time to do it, but it totally escaped my mind. Will get all that squared away tonight for you :thumbup:Done and fixed for you Tom -- ready for testing whenever you get a chance! :biggrin:

[Tomcio]

This is a final update for this project.

Well, as cool as this project was it is now dead. This was one of those little things that really annoyed me and I was hoping to fix it. The problem I'm talking about is no hot air from the center vents. There was plenty of heat coming out of floor or windshield vents but center/door vents can only get cool air. I wanted to kill two stones with one bird and in the process of improving the air distribution I wanted to convert all flap actuators from vacuum to digital servos which would allow removal of the mode switch and temperature knob.
Unfortunately I am not able to continue with this project. The flaps will be restored to original state and all vacuum actuators will be re-installed. That poor POS mode switch goes back in the center console.

I'm sorry but this project is now DEAD.