Stuck on defrost?? wtf?

LightEMup

Registered User
Ok one day i noticed that the little blue lights on the vent, max ac, def ect...buttons stopped working, also u can press any button u want and it will stay on defrost/floor, but i can still turn it from low to high...is this just a loose wire since the lights went out at the same time? i can also control the temp too.
 
That function would be controlled by vaccume. Check the line comming into the fire wall. Do you hear and hissing sound when you change the selector or movement of the doors the direct heat and air? If not you have a line off or broken hose. You might need a new climate control as well if you have vac to it.
 
scbird1 said:
That function would be controlled by vaccume. Check the line comming into the fire wall. Do you hear and hissing sound when you change the selector or movement of the doors the direct heat and air? If not you have a line off or broken hose. You might need a new climate control as well if you have vac to it.
hmm, so the lights going out on the selectors has nothing to do with it huh?
 
where is this vacuum line located? i opened the hood and remembered how simple these engines are, and how there's only like 2 wires and a hose or two behind the supercharger...haha YEAH RIGHT!!!! haha i just need to know what general area to look in and how to tell if its bad
 
I believe your 2 problems are unrelated. Light bulbs in the climate control system sometime burnout. There is one in the fan speed selection switch and there are two on the top of the unit that lights up the buttons. You need to pull out the climate control unit to get access to them.

Air is directed to the top of the dash, the vents, and the floor using vacuum controlled doors. When you have no vacuum, the default is "defrost" and from my past experience, I found the problem in the engine compartment, before the vacuum makes it to the climate control unit. Trace the vacuum hose from where it passes through the firewall (passenger side, near the relays and a/c evaporator) to the tee junction ( near the mid point of the firewall and looks like a saucer with a tube going out the bottom and branches into 2 connectors with the bottom one feeding the vacuum to the climate control unit. It is secured under the wiper assembly with a nut). The tee junction may be broken or the bottom hose may have been pulled off. Check the vacuum hose for nicks or holes. Failing that, the vacuum connector on the back of the climate control unit may be off (can happen if someone popped out the climate control unit or radio).

Check those out. If that didn't work, post your findings and you might need to be lead through the next phase which is more complicated - tracing the red, white, and blue vacuum hoses, checking the 3 vacuum motors, and seeing if the doors are binding.

Good luck.
 
Steve Richards said:
I believe your 2 problems are unrelated. Light bulbs in the climate control system sometime burnout. There is one in the fan speed selection switch and there are two on the top of the unit that lights up the buttons. You need to pull out the climate control unit to get access to them.

Air is directed to the top of the dash, the vents, and the floor using vacuum controlled doors. When you have no vacuum, the default is "defrost" and from my past experience, I found the problem in the engine compartment, before the vacuum makes it to the climate control unit. Trace the vacuum hose from where it passes through the firewall (passenger side, near the relays and a/c evaporator) to the tee junction ( near the mid point of the firewall and looks like a saucer with a tube going out the bottom and branches into 2 connectors with the bottom one feeding the vacuum to the climate control unit. It is secured under the wiper assembly with a nut). The tee junction may be broken or the bottom hose may have been pulled off. Check the vacuum hose for nicks or holes. Failing that, the vacuum connector on the back of the climate control unit may be off (can happen if someone popped out the climate control unit or radio).

Check those out. If that didn't work, post your findings and you might need to be lead through the next phase which is more complicated - tracing the red, white, and blue vacuum hoses, checking the 3 vacuum motors, and seeing if the doors are binding.

Good luck.
hmmm, i think best buy pulled my radio out when they were putting in a 10 disc changer, so that could be the problem. thanks for your help man, i needed a detailed explination like that :)
 
LightEMup said:
hey how do i remove the climate control to check to see if the vacuum hose got disconnected??
On my car I needed the Ford Stereo tools, 2 "u shaped clips", insert thr clips at either side of the unit and wiggle until it unclips. then slide the whole assembly forward.
 
Some car parts places sell them as part of an antenna wrench kit.

Instead, you can get a coat hanger, cut 2 pieces about 6 to 8" long and bend them into a u-shape. Insert the ends into the holes of the climate control unit at each side, gently swing the u-shaped ends towards the center to release the clips, and at the same time pull towards you and jiggle the unit. You should be able to pull the unit out about 2 to 3 inches. Be patient so as not to damage the holes. On the back of the unit, from left to right, is the fan speed connector, the blend door control for temperature, and the vacuum hoses. The vacuum hoses are secured to the posts using push clips - be careful not to break the posts. Without these tiny clips, the hose connector might work itself out on its own.

On the top of the unit you will see 2 grey plastic pieces that are slotted - these are your two bulbs to light your climate control unit. Ford still sells them. Now is a good time to replace them.

Good luck.

Hope this helps.
 
Climate Control Harness

Does anybody know where I can get this rubber vacuum harness? 1991 SC. I may just try to hot glue around it to seal it back up.
 
Good afternoon

Three suggestions for the HVAC hose repair.

Go to your nearest salvage yard. Get a 1989 - 1993 Thunderbird/Cougar HVAC hose/block connector assembly. Plug and play.

Go to your nearest auto part store. Dorman #47418 5/32" vacuum hard lines plus 1/4" heavy duty electrical heat shrink if connections are needed.

Order silicone hose. http://www.mscdirect.com/product/48635932.
 
Does anybody know where I can get this rubber vacuum harness?

It is a hard plastic, vs. rubber/silicone, which tend to collapse under vacuum (not pressure) as found in these circuits. Might be best to avoid the risk if you DIY, especially when the proper material should be readily available, if you can't find OE components.

As noted, these are not specific to the SC, and there should be plenty of 'bird donors in the wrecking yards. I didn't spot any on eBay, but maybe someone here as what you need laying around. Consider posting in the 'want ad' section.

Take a look at what's involved under the dash if you choose to replace hoses and ports/manifolds etc. If you can find the right plastic hose, and an in-place repair can be trusted, DIY might be simpler. At least you know the problem now ;)

Good luck and Happy Holidays.
 
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