| Author |
Message |
Steve Magnusson (91tr)
| | Posted on Sunday, August 12, 2001 - 1:25 pm: | |
Steve -- Recently, I've had a chance to study the TR AC electrical systems rather closely, because (like other new TR owners) I was a little surprised to find that there's no provision to allow just fresh air venting/blowing so I'm working on developing a (hopefully simple) switch/wiring modification to add this "fresh air" functionality (but that�s a different story).
First, I want to say that the TR AC control system is a rather complex thing so it's great that you're getting the WSM (and please don't hold me to any guarantees for free advice). One caution is that the AC schematics in the WSM reflect the early TRs, and, from an AC function point of view, match the AC schematics shown in the 459/86 TR wiring diagram manual. For later US cars, the AC system wiring/control is a little different, and the 509/88 TR wiring diagram has the correct AC schematics for those cars. From reading the tea leaves in the TR SPC (587/90), I believe US cars after SN 79904 are the later AC design per 509/88 while US cars up to 73495 are per the WSM or 459/86 design � I�m unsure about the US cars in-between.) Still, both system share a lot of functional similarity, so the symptoms you describe are still useful for some checks you can try regardless of which version AC you have:
1. The blower system and the remainder of the AC system share the same +12V power input line -- so since your blower system is working OK, the fuses and the relays on the fusepanel are probably all OK.
2. When you push a button to turn on the AC system two things happen:
A. the vacuum source is connected to the appropriate combination of actuators on the AC unit itself to move the various lids/flaps into the proper positions, and
B. Two wires (both yellow/green) are �grounded� by the AC pushbutton unit -- these �grounded� wires go to power the blower system, and they also �activate� relay (lower case) �c� (on the later cars) or relay (lower case) �d� (on the early cars) -- these �lower case�-labeled relays are on the AC unit itself. For both the early and late design, when these relays are closed, +12V is applied to Pin I (the green/white wire) on the AC ECU (which is mounted in the cavity behind the fuse panel). If, with the key �on�, and an AC pushbutton pressed, you don�t get +12V on the green/white wire then the relay �c� (late) or �d� (early)on the AC is the problem. (This is a little tricky since you need to first remove the fuse panel to get access to the AC ECU connectors and then reinstall the fuse panel and plug it all back together before testing.) When you�ve got access to the AC ECU connectors you can also make the resistance checks on Pins 1 thru 6 for the three temp sensors and the temp control knob as described in the WSM. And with just the key �on� there should be +12V on Pin III (3 brown wires)of the AC ECU (but this is the same +12V used for the blower function so if that�s working this should be OK)
3. When the AC ECU wants to �turn on� the AC compressor clutch, it puts out +12V on Pin II (2 orange/black wires) of the AC ECU. At the bottom of the fuse panel are 4 horizontal 12-pin white connectors -- this orange/black wire passes thru connector �k� (the upper one on the left side when facing the fusepanel) in the 4th pin from the left so you can measure it there. Even if this lines goes +12V, the AC compressor clutch may not come on (because of the high and low pressure switches downstream), but at least you can tell if the AC ECU is trying to turn on the AC compressor clutch. As an aside, the main +12V power to run all of the AC system passes thru 2nd pin from the right on the �k� connector (a huge brown and a small brown wire) � wouldn�t surprise me if you see a little �cooking� around this pin.
Good luck with the fix... |
Warren E. Smith (Magoo)
| | Posted on Friday, August 10, 2001 - 10:30 pm: | |
P.S. Check all the fuses, you can tell if any are blown. |
Warren E. Smith (Magoo)
| | Posted on Friday, August 10, 2001 - 10:28 pm: | |
Steve, Is the suction line of the A/C compressor getting cold when the car is running and the A/C compressor is energized? |
David Harris (Dakharris)
| | Posted on Friday, August 10, 2001 - 10:18 pm: | |
Is it possible that the control is not connected? Have you worked on the interior lately? |
Steve Marschman (Hossheim)
| | Posted on Friday, August 10, 2001 - 4:20 pm: | |
I have an '88 Testarossa. The heating/air conditioning system does not heat or cool. The fans blow air, the air speed is adjustable, and the vents work fine. However, I can get no heat when the control is turned to "red," nor can I get cool air when the control is turned to "blue." I checked the 20 amp a/c fuse and it is intact. I haven't checked any other fuses as I don't know which ones may be related to the heating/cooling system. Does anyone have any pointers for how to go about diagnosing the system? Is there a computer that runs the system that may be bad? I should be getting my workshop manuals next week, but if others have any helpful hints, I will be most grateful.
Thanks
Steve |
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