Climate control problems? Read This!

[sly]

that looks like the one that should go to the vent actuator. Should be far right behind the glove box, just above the kick panel.

[colognecapri]

since engine coolant is used to make the heat, yes. It will not be warm until the engine gets warm.

The temp control adjusts the ambient air temp sensor which controls the blend door position through vacuum. Without the ambient air temp sensor working right AND completely hooked up properly, the temp control will not work much at all.

I totally understand you need hot coolant to make heat ( I may be dumb but not that dumb ), but since on a cold day the car has piping hot heat for a few minutes as it gets up to full temperature (which again is hard to tell since theres no temp gauge), in the past I thought that somehow it might be related to the car reaching a certain, "full operating temp" coolant temp....in retrospect, even though the car has iron block and heads, 10-15 minutes is a long time to reach warm up even in cold weather with the car being driven at fairly high speeds....it probably has nothing to do at all with the coolant hitting a certain temp, but is totally related to the ATC sensor.

[gadget73]

I think sly is right about the vac line, its probably the fresh air/recirc door actuator behind and slightly below the glovebox. If there is a can there with nothing connected, that'll be what goes there. If it doesn't reach that area, there are 3 vacuum motors behind the radio area. See if one of those is missing a connection.

[colognecapri]

I think sly is right about the vac line, its probably the fresh air/recirc door actuator behind and slightly below the glovebox. If there is a can there with nothing connected, that'll be what goes there. If it doesn't reach that area, there are 3 vacuum motors behind the radio area. See if one of those is missing a connection.

I am going to check it out this this weekend. If it is the one that you guys are leaning towards, would this cause the poor heat/temp selection issues I am facing or is it still probably the ATC sensor?

Also, I noticed on this form of ATC there is no clear "MAX A/C" or "Recirculate" mode like most Fords have. So, does the car decide to use recirculate in certain warm weather conditions under A/C settings as long as you aren't in Defrost modes for max A/C effectiveness?

Not to ramble on, but does anyone else think its bizarre that a 80's Box Body with ATC has a bilevel (dash vent and floor) setting on the climate control yet from what I know, none of the 92-11 cars that I've seen do (not counting LTCs), even those with EATC!?!?

[gadget73]

no, it might cause it to go to hot defrost on acceleration, but thats about all it does. With the vac line unhooked, it pulls fresh air from outside all the time. If the vac motor gets vacuum, it pulls air from under the dash. Usually its only on recirc at full hot or full cold. I'm pretty sure thats what the vacuum valve on top of the blend door assembly is for. At least I assume so, because nothing else makes much sense.


The bi-level thing was only on ATC cars too. Manual climate control didn't get that. Its basically the addition of one vacuum motor and a modified air door in the plenum. Instead of one big door, its got a dutch door sort of thing. One vac motor works a small door cut in the middle of the large one, and the other motor works the whole large door. It doesn't work fantastically well, so I guess it was decided to just scrap the idea, or maybe it would have cost more to implement the controls for it and nobody wanted to spend the money.

[Mainemantom]

I printed this entire thread for future reference. Thanks Gadget 73 !

[colognecapri]

Thanks for all the help guys! I got a smoking deal ($23 shipped instead of $100++ at auto parts store)on a new old stock (made if 96) ambient temp sensor on Ebay by searching for the secondary part # from the picture of the box on the first page of this thread. My heat is now hotter than ever and I have access to the full range of temperatures that I've never had before, as well as the automatic mode working properly on the blower speed control. The car has ice cold, R134 converted A/C so I now have fully functioning ATC climate control, I'm so happy I won't be freezing all winter!

I'm still trying to figure out where that mystery vacuum line goes before I button up the dashboard/glovebox ( I took it apart farther than really necessary). Also, it appears my car has a bad thermal blower lockup switch as the fan is currently refusing to blow on "floor" mode even after the car has warmed up for several minutes. I'm about to test that and decide whether to bypass it or buy a new switch. Thanks again for the help!

[sly]

to test that, unplug the electrical from the thermal lockout and shove a paperclip into the harness (or otherwise jumper the wires together) and keep it from grounding out anywhere. If the blower turns on... the lockout is the problem.

[Toploader]

Gents,
Per so many suggestions concerning my a/c:
Replaced the plastic a/c valve, the one with two vac lines, one to the can, the other in the car.
New Blower Motor, and resistor, replaced the vac line(s). but not the can.........I charged into the system some PAG oil to make up for the compressor leak (till I can put the cash together for new parts) .........blows nice n cold..........temp out of the dash vents was about 39-41 degrees. But I find that out of the clear blue the blower motor goes from high speed down to low on its own, and it does not always happen with different throttle speeds..........question, should I continue to search for a new vac can?............I can not seem to find one that can sub in to my '86 MGM 5.0?.............

[sly]

ATC will do that when you get near the temp you have selected with the slider.

[Toploader]

Sly, this forum is just the 'sheet'......most of the time I keep the ATC control slider down near 60, and never thought the blower slowing down was caused by the system sensing the cabin as too cold and since the slide was at the coldest position, slowing down the blower speed is the only way to get the temps to rise slightly. Do I have the basic idea? I assumed I needed a new vac can.

ATC will do that when you get near the temp you have selected with the slider.

[sly]

if you got it that cold in the cab... yeah. If you have the slider all the way on 60, it shouldn't get there for some time and then you'll be freezing unless well "suited" to that temp. (Pun intended)

I generally keep mine on ~75 unless it gets bugger hot out. When it gets to that temp the "ambient temp sensor" cuts the vacuum to the big can on the blend door. As that moves to a more central position, the fan goes to lower speeds. In the Mark, fan High is the "auto" position. In my 88, the lowest setting actually says "Auto" and that's where it stays most of the time. There is a module somewhere that detects the blend door position or the vacuum to it and adjusts the fan speed accordingly. Central position is low, hot or cold position is high, and medium is between those two points.

[Toploader]

Sly, how do I determine if the vac can is bad, or if as you said the slow speed of the fan a result of the temp adj of the ATC?

[sly]

if you have a vacuum pump, pull the vacuum line to the can and put the pump on it and pull a vacuum on the can. if it holds it and does not degrade, it's fine. Otherwise, replace it. If it's the ATC control, switching to high should bump the fan speed back up and blow fully cold air out. If the air isn't cold, but lukewarm or hot, then there's a vacuum issue.

[Toploader]

Sly I keep the blower switch on the high position, so I can not switch it, the blower slows down from this position.
I tend to not keep the fan switch on the auto position.