| Author |
Message |
Steve Magnusson (91tr)
| | Posted on Friday, December 14, 2001 - 2:43 pm: | |
magoo -- You've got the general gist right, but either heating or cooling can be recirculation or fresh mode (i.e., the airflow pattern is independent of desired temperature). The AC evaporator and the heater core are basically right next to one another so all of the input air (whether it comes from the outside or from inside the cabin) always passes thru both (and then on the output side of things the air is either directed out the main cabin vent or to the windshield for defrosting). As you said, the key factor is that the output air temperature is controlled by the amount of hot water passing thru the heater core -- not by any plenum motions.
Bruce -- I rechecked the TR WSM, and it states that the air temp coming out of the vents should be within +/- 1 deg C of the cabin temp at equilibrium so I think you do have a problem somewhere. |
magoo (Magoo)
| | Posted on Thursday, December 13, 2001 - 11:48 pm: | |
So Steve, What you are saying is on the TR the heater valve regulates how much hot water flows through the heater core to mix with cold air to reach a desired temp in the cockpit. Then the plenum door only regulates how the air is directed in the cockpit between the upper and lower vents and there is only a recirculation mode on the A/C. |
Steve Magnusson (91tr)
| | Posted on Thursday, December 13, 2001 - 12:21 pm: | |
Patrick -- the TR AC vacuum lines only work to move the various internal air flaps around (for air distribution) so if your heater "works fine" (i.e., you get air blowing out of the appropriate places) then no vacuum can't be the problem for your no cooling situation. A couple of questions:
1. Can you see freon movement in the sight glass on the dryer (when the AC is running of course)?
2. Have you measured (or had an AC shop measure) the low (suction) and high (discharge) pressures at the AC compressor when the system is running (and engine at ~2000 RPM)? (Fortunately: A. this is not Ferrari specific so any AC shop should be able to measure the suction and discharge pressures, and B. there's no disassembly required as the pressure fittings are easily accessable on the AC compressor.) |
Patrick S. Perry (Psp1)
| | Posted on Thursday, December 13, 2001 - 12:01 pm: | |
I think the vacuum lines to my A/C air control box are leaking or broken - I'm not getting cooled air out of my system at all (compressor is activated and there is freon in the system)but the heater works fine. Where do the vacuum hoses go from the engine compartment? Do they go to the rheostat in the console and the to the distribution box in the front or straight to the box? How do you get to the distribution box where the controls are? - please tell me it's not through the dash, that doesn't look like fun at all!
Since I'm in Southern California where being too cold is not a problem, can the plenum door be opened manually so that the A/C would work until I can work on the proper "fix"?
Thanks in advance! |
Steve Magnusson (91tr)
| | Posted on Thursday, December 13, 2001 - 9:21 am: | |
Ben -- I think relocating the power transistor is not a bad idea, but depending on the failure mode of the transistor, I think you may or may not be able to leave the "old" one in place (although I haven't studied this in detail so maybe with the right cuts/jumps it could be). I just wanted to point out that there's more in the TR AC fan food chain than just the (expensive) rheostat switch. I am surprised that the designers decided to put so much electronic/electric stuff (even relays!) directly on the (difficult to access) AC unit itself.
magoo -- The vacuum-actuated doors on the TR AC unit do control where the air goes into and out of on the AC unit, but their physical positions (or gasket deterioration) are unrelated to the temperature control of the output air stream (i.e., when max AC is called for the system relies only on the hot water valve closing properly). |
magoo (Magoo)
| | Posted on Wednesday, December 12, 2001 - 10:39 pm: | |
Steve, Isn't there a plenum door that is activated when calling for recirculated air or fresh air? This is the same door that regulates heat or a/c when you are calling for Max a/c. Sometimes the foam seal will deteriorate around these doors and allow heat to by pass in the max a/c mode. |
Ben Lobenstein 90 TR (Benjet)
| | Posted on Wednesday, December 12, 2001 - 10:31 pm: | |
Steve M - If the power transistor fails, it can be fixed without a Dash-echtomy (and probably a BETTER fix too, just not placed back into the same place).
-Ben |
Steve Magnusson (91tr)
| | Posted on Wednesday, December 12, 2001 - 11:23 am: | |
Bruce -- I still think that you have a problem with either the PWM drive to the hot water valve (the AC ECU could be fritzed or the hot water valve itself could be sticking) or the thermistors sensing the various temps related to the AC unit are wacky. Have you performed the diagnostic measurements at the AC ECU connector (located behind the fusepanel) listed in the WSM? (There is no "plenum" action that I know of involved in balancing the hot/cold air delivery.) I can confirm that with ~30 deg F outside temp and 68 deg F inside cabin temp, the air temp coming out of the interior vents (at equilibrium) is about 68 deg F.
Adam -- The AC fan rheostat switch controls a power transistor that then controls the AC fan blower motor speed -- either can be fritzed. The rheostat switch is (much) more expensive but easier to replace, while the power transistor is mounted on the AC unit itself so this requires a complete dashectomy. |
Michael A. Niles (Man90tr)
| | Posted on Saturday, December 08, 2001 - 11:06 pm: | |
Skyking,
The more I think of it , I think magoo is on the right track with his advice. |
Adam Goldman '86 TR (Icnsltmfg)
| | Posted on Saturday, December 08, 2001 - 10:19 am: | |
I will put the switch replacement on the little things to work on during the winter. I also want to repair the arm rest cover as all of the bolts are loose, and the only way to fix it is with the center unit out of the car. I have had very few problems with the car ( knock on wood . I have to take a few more photo's in the next few weeks.
Adam |
Michael A. Niles (Man90tr)
| | Posted on Saturday, December 08, 2001 - 7:15 am: | |
Adam,
Your fan rheostat switch is bad. Mine started to behave like that 2 days after i got the car and they replaced the switch and I have excellent flow control now. I wasn't charged for it but I think the switch is around $150. takes 15 minutes to change. |
1989 328 GTS (Vilamoura2002)
| | Posted on Saturday, December 08, 2001 - 1:41 am: | |
Adam, your one mirror TR is beautiful.
She is for me the most beautiful TR model, specially red/tan.
Does she give too much trouble apart from the normal things?
Got some more photos of her? |
Adam Goldman '86 TR (Icnsltmfg)
| | Posted on Saturday, December 08, 2001 - 12:40 am: | |
Bruce;
Mine workes pretty well from a temp stand point, but the fan is so tuchy, that it is almost on or off. I think there is something wrong with yours, and the dealer is just plain wrong. |
magoo (Magoo)
| | Posted on Friday, December 07, 2001 - 11:34 pm: | |
Bruce it sounds like a plenum door is not shutting all the way to eliminate the heat when the comp. recycles and cuts off the cold air. The comp. cold air probably overcomes the heat coming through the door until the comp. shuts off, then the heat comes in full force because the door is not fully closed. Just a theory, Magoo |
Michael A. Niles (Man90tr)
| | Posted on Friday, December 07, 2001 - 11:10 pm: | |
Skyking,
Your dealer is incorrect. The car does much better than he says. I set 69 in mine ( in fact I rarely move it) and it does this -- if very hot the AC comes on and cools it down. After that it does fine. The AC or heat cycles when necessary BUT it does so very smoothly and the temp coming out of the vent is pretty darn close to what I set. Obviously it is a somewhat cooler or hotter than the inside but I do not get super hot or super cold stuff like you mention. For example, I can rarely tell when it cycles it does such a good job. It is possible that your HVAC ecu is acting up.
One suggestion. Take a moist cloth and clean the outside of the temp sensor (its on the driver's side on the lower part of the dash). It is possible that it is dirty or when cleaning it you go some gunk on there and its actually cycling to the gunk's temp extremes instead of to the air in the car. Just a thought.
Hope this helps.
Michael |
Jay Thompson (Jayt)
| | Posted on Friday, December 07, 2001 - 8:49 pm: | |
My 88 TR works fine - once it is warmed-up. I set at about 4:00 more to cold side. The temperture is not very steady because cold is basicly controled by cycling the compressor. Make sure the "normal" button is pushed. I also noticed there is a compressor "cut-out" at high revs. |
Bruce Warwick (Skyking)
| | Posted on Friday, December 07, 2001 - 8:18 pm: | |
Hi Guys:
I need some help/advice re the A/C and heat on my '88 TR. On any car I've ever owned, I can set the thermostat for a comfortable "blend" of cool and heat. With my TR, I get [as you would expect] full cool air set at max. cool, and full hot air set at max. heat. BUT, when I select any temperature in between, there is NO blend of cool/hot air. Set the thermostat in the middle position [for example at where 72 degrees F would be], and I get full cool air. Then, when the compressor cycles [and stops],out comes full hot air! Even when it's 90 degrees outside. Wierd.Then, on goes the full cool again.This is how my system maintains the overall temperature inside the car of 72 degrees.
Do all TR systems work this way?
I took it to the dealership who reviewed the manuals and they say this is normal for the TR as it is a very primitive system! It is all hot or all cool, and each takes it's turn to maintain an even temperature of ,say, 72 degrees F. There is no blending of temps.so that 72 degrees comes out of the vents.
So what do you say guys? Do your TR temp. control systems work like this?
Bruce. |