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Where to start with heater control problems?

sorry again, that "edit" was done the same day he posted it, i was watching this from the start, still :waytogo:
 
British Slave said:
I have the vacuum schematic right here in front of me, but I can't post pics.
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Yo Brit,

Go to www.picturetrail.com. Create a free account (I haven't gotten any spam or anything) and upload pics. once the pic is uploaded, at the top of picture trail website select "get picture URLs" then just copy and past the "forum image" code to your forum post and it will show up.

Or become a paid member to Ck5 which from what I can tell would be a very sound investment (it is on my list of things to do!!:D)

****edit*** becoming a member is on my list of things I "did".
 
Jessie James said:
I hope this helps... remember my truck is a 1991.
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Jessie, Thanks for the pics!! that is one huge tangle of vacuum lines!

So I have the black ball...but all the rest is gone. I never had whatever that EGR looking thing is on the firewall that half of those vacuum lines are going to...(unless that was cruise control...I did take that out:confused:)

O.k. well, I can hook up the black ball to a vacuum source and make a new vacuum line, but once I go through the hole in the firewall will it be obivous where to go from there?

Vacuum%20lines%200722.JPG
 
I do have a cruise control, so that is probably what the lower right round thing is - it's right in line with the throttle cable. The other part, under my fingers, probably goes down to the manifold for the vacuum source. On the older trucks it may even go straight to the carb, but I have TBI so maybe it's routed differently.

Oh, and ignore the melted firewall. That's from when my truck caught on fire. :haha: :whistle:
 
The big vacuum diaphram in the lower circle was for the cruise control. Make sure any feed lines for that system are capped off.

The other circle is a check valve to hold vacuum in the system. This should be close to the vacuum source before it tees off into the vacuum ball or the hvac system.
 
I recently did my heater core in my 89. IIRC, the one vacuum line comes through the fire wall and then is "jumped" to several smaller diaphrams behind the heater/ AC/ vent duct behind the glove box. What you are seeing by looking directly into the glove box is the top side of that duct and the mechanical control linkage. The diaphrams and vacuum lines run between the duct and the firewall. Mine had little clear rubber type "nipples" on them where they attached to the diaphrams. These "nipples" have a loop on the end and hook onto the 90 degree fittings on the diaphrams to keep the vacuum lines connected.

I think that the mechanical linkage is for the temp or blend door, mixing outside fresh air with either heated or cooled air from the system.

The vacuum lines and diaphrams will deflect the air to the floor, vents, or defrost.

At least that's the way I understand it, and it appeared to me.

Been wrong before....:thinking:
 
I HAVE DEFROST!! Thanks to all the help, I bought 5 ft of all sizes of vacuum line and an assortment of Ts and connectors. After about an hour I cobbled together a line between the the vacuum canister and the outlet on the manifold and I FOUND THE BROKEN line going through the firewall. Luckily one of my rubber vacuum hoses slid perfectly over the broken stub of vacuum line.

Started the truck moved the selector for heater controls and I was treated to the sweet symphony of clicks and hisses as the magic happened behind the firewall!:D Switched it over to defrost and after allowing for the clicks and hisses, I could feel a slight breeze eminating from the defrost vents!!!:woot:
 
Start it up now, let it get warm and check again if in fact you have heat hitting the windshield.

Not sure what's going on with mine, but i only get "heat" out the vents, all other air movement selections work, but as soon as i select for the heat to go to the floor, or defrost, it goes cold.

Also i am sorta hijacking if anybody has ideas as to where or what i should be looking at with it :D

ans mine DOES have a factory heater control valve in the engine compartment, hooked to both front and rear heaters.
 
4x, yes I do in fact get hot air from my defrost vents. The function of switching vent position and the function of hot or cold air are two different seperate systems as far as I can tell. So it is very possible that your vents are switching to allow air flow to the defrost vents, but something is heppening that the hot air setting is switching back to cold air???

You can see both of these control pivots if you take out your glove box, you can watch them move as you change your controls. The temperature blend box is wire driven (At least on my 89) so you can move that with your truck off. The vent position controls are vacuum driven ( as I'm sure you know unless it is non-A/C)

If you have A/C, at least on newer cars, full defrost actually uses the A/C to cool the air (to de-humidify it) and then heats it with your heater to make it SUPER dry (absobant) so that when it blows on your windshield it it can dry of any condensation or fog.

maybe your A/C is cooling it down and your heater is hot enough to overcome the cooling action when in defrost? Did you let your truck heat up completely?
 
AC doesn't work :doah:and yes it's been on long road trips where a defroster would have been nice at times.
I just haven't really been too motivated to check into the issue with mine. But living in a colder weather climate state now, i'm thinkin i need to get off my but pretty quick :p:
 
Mine is making hissing noises when you move the controls, however it wont blow full force thru the ac vents, its like its stuck on bi-level because it blows on my feet and just some out of the dash vents.
Since I have a hiss....should I focus looking for some vent/door problem under the glovebox?
 
88jimmy4x4 said:
Mine is making hissing noises when you move the controls, however it wont blow full force thru the ac vents, its like its stuck on bi-level because it blows on my feet and just some out of the dash vents.
Since I have a hiss....should I focus looking for some vent/door problem under the glovebox?
Click to expand...
You have a vacuum hose leak, the hose that controls the flap to direct the air flow is either pulled off or cracked.
You should look under the dash and try to find the source of the hissing.
 
AKbigsub said:
I can't believe that nobody has mentioned the little plastic piece that connects the blend door linkage to the blend door. It is a very common part that breaks and is still available at the dealer.
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:bow::bow::bow: That's exactly what my issue was:doah: Its a tiny white plastic part that is screwed to an actuator rod and connects to the door. If it fails the door fails open hence AC blows across the floor. MY fix was I made a plastic plug that fit into the bottom vents that blow on the floor and forces the AC out the dash vents. :dunno: I'm lazy that way :rolleyes:
 
88jimmy4x4 said:
Mine is making hissing noises when you move the controls, however it wont blow full force thru the ac vents, its like its stuck on bi-level because it blows on my feet and just some out of the dash vents.
Since I have a hiss....should I focus looking for some vent/door problem under the glovebox?
Click to expand...
Removing the box and FIXING the little plastic part will take you 16 hours of time you will never get back. Just plug the bottom floor vents with your hand and notice the air blowing hard from the dash vents:eek1: Then get industrious and plug those vents and voila :eek1::waytogo:
 
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