| Author |
Message |
Henryk (Henryk)
Junior Member
Username: Henryk
Post Number: 172
Registered: 8-2001
| | Posted on Sunday, August 18, 2002 - 9:27 pm: | |
Steve: I will start a new thread.....one that relates to A/C......that way, others can possibly learn too.
Thanks for all your help!
PS: I just recently bought a digital camera, and am trying to figure it out. I took some great pictures of the cars, but had the setting on too high.....resulted in a too HUGE picture. I will eventually post a picture in the profile. |
Steve Magnusson (91tr)
Member
Username: 91tr
Post Number: 950
Registered: 1-2001
| | Posted on Sunday, August 18, 2002 - 9:14 pm: | |
Henry -- Glad you found the problem. I'm not really sure how you would proceed if you have a really big leak since I think you won't be able to pull a decent enough vacuum prior to recharging -- can someone comment?
PS -- you at least need a shot of the 512BBi in your Profile! |
Henryk (Henryk)
Junior Member
Username: Henryk
Post Number: 171
Registered: 8-2001
| | Posted on Sunday, August 18, 2002 - 8:13 pm: | |
Steve: You are right!!!!!....NO FREON! Interestingly, this would confirm that the pressure switch is probably OK. The zero ohm reading would be consistent with not having freon in the system, or VERY low. The switch requires a minimum of 2 Bar of pressure to allow the compressor to kick in.......less than 2 and the switch opens, to prevent the compressor from running dry.....since yours is full, that is why you had an OHM reading, and I did not. This seems an easy way of testing, wouldn't you agree?
With the WSM and your help I have really learned a lot about the A/C electrical system.
Back to the problem: I will assume that the electrical wiring is OK. I have just won, on eBay, an A/C recharger, for R12 and R134a. It includes a full (propane grill tank size) of each. I hear that R12 is not cheap, so I think I got a deal!! Without just putting good Freon in, is there any way of putting something else in, to find the leak?.....that way it can be corrected, followed by charging with Freon.
Thanks again.
BTW I saw your profile. VERY nice TR......SO is the house!!!!! |
Henryk (Henryk)
Junior Member
Username: Henryk
Post Number: 170
Registered: 8-2001
| | Posted on Saturday, August 17, 2002 - 10:40 pm: | |
Steve: I will do as you ask, but it will have to wait till tomorrow to get the results back to you. Interestingly, I was already on e-Bay looking to bid on those A/C pressure gauges! I agree that this seems to be the next logical step.
I will let you know the results tomorrow. |
Steve Magnusson (91tr)
Member
Username: 91tr
Post Number: 946
Registered: 1-2001
| | Posted on Saturday, August 17, 2002 - 10:08 pm: | |
Henry -- sorry I wasn't clear -- my question is with the engine running and the AC "OFF" button pushed is the voltage on Pin I OV or 12V? (should be 0V IMO and then go to +12V if any of the other 3 AC buttons is pushed). I don't think the heater valve is your problem as +12V on Pin 4 should keep the heater valve closed -- have you tried running the heater at maximum to see if extra heat comes out and then turn the temp down to cool to see if the heater valve closes and the temp of the air coming out of the vents at least drops back to ambient? I'd still say you need to verify whether you actually have any (or enough) refrigerant present before resorting to replacing the max/min pressure switch. Have you tried briefly opening one of the Schrader valves on the compressor to see if any refrigerant comes out? I bought a cheapy set of high/low AC gauges and have found them very useful (in usually confirming a problem) -- perhaps you should do the same. |
Henryk (Henryk)
Junior Member
Username: Henryk
Post Number: 169
Registered: 8-2001
| | Posted on Saturday, August 17, 2002 - 9:42 pm: | |
Steve: Thanks for taking the time to check the ohm reading on the pressure switch......I will assume that mine needs replacement.....next time I am in Chicago, I will check the ohm reading on a NEW switch, at the dealer, before I buy one...with zero pressure. Since the A/C went out all of a sudden, leads me to believe that there is pressure and freon in the system, but I could be wrong. I agree with you that it should blow cold, if I engage the compressor manually.....however, if the heater valve is in the heat position, then, it would indeed be difficult, since the heat could cover up the cold?????????????
The SM states that only two sensors are involved in determining whether the heat, or A/C, comes on....it compares the reading from the in-car temp. sensor, to that of where the temp-is-set-at sensor (the round rheostat dial). It then engages the water heater valve (to get heat), OR the compressor (to get cold), but never both. It doesn't have anything to do with the buttons.
Pins I,III, and IV where 12v, and pin II was 0v.....however, I neglected to check which button I had pushed. I will try this tomorrow, and take readings with the various buttons pushed......I really don't expect a change, since there is NO A/C button to speak of. My understanding is that the first button (has 3 circular arrows), is for internal circulation......the next button (3 swiggly lines), is for outside air. The buttons appear to only regulate which vents are open.....of course, the OFF button shuts everything down. The manual makes it quite clear that only the comparison of the ambient in-car temp., with that of where one sets the temp. at, are the only two factors that set either the heater, or A/C in motion.
If it is the pressure sensor, will I loose freon when I remove it?......or is there a Schrader valve there?
Thanks again for your help, and especially your patience!!!!!!
|
Steve Magnusson (91tr)
Member
Username: 91tr
Post Number: 941
Registered: 1-2001
| | Posted on Saturday, August 17, 2002 - 8:18 pm: | |
Henry -- I just measured the resistance of my max/min pressure switch (engine off, key off) and it's about 0.2 Ohms. Yours could be bad, or it could (correctly) be indicating that you have no refrigerant in the system (your manual test engaging the AC compressor, yet no cooling, would indicate the same thing IMO). As I understand it, the "smarts" in the AC ECU look at the various sensor/command inputs and then it decides to either engage the AC compressor clutch and/or actuate the heater water valve -- but once the AC clutch is actuated, the cooling process should take place regardless. I'm a little confused by your description of the voltage measurements -- are you saying Pin I on the AC ECU is +12V with the key on regardless of whether or not you push an AC button down? (And Pin IV should be at +12V if you're asking the system to cool -- +12V on Pin IV closes the heater water valve). If your sensor/command inputs to the AC ECU are good (and you're asking the system to cool) yet Pin II never goes +12V is troubling, but I wouldn't worry about it until you can get the system to cool when you manually force the AC compressor clutch to engage. |
Henryk (Henryk)
Junior Member
Username: Henryk
Post Number: 168
Registered: 8-2001
| | Posted on Saturday, August 17, 2002 - 7:05 pm: | |
Steve: And I was hoping it would be something simple!!!!!Not my luck!
When all else fails, read the WSM. I spent 3 hours on it, over a long lunch, and then I tackled the problem. Here goes:
I found the control unit, together with the 6 prong (marked 1-6), and the 4 prong (marked I-IV) plugs.
What is interesting is that in the 6 prong plug, number 1 is ground, and nos 2-6 go to the various sensors connected to the A/C system. There is a chart in the SM that shows the various resistance figures one should get at various ambient temperatures for each of the sensors, depending on what 1-x combination is used......one for each sensor. All readings where within normal, and moving the temp dial changed the resistance accordingly....hence, all sensors are OK.
On the 4 prong plug, nos. I, III, and IV show 12v with ignition on, and no.II shows 0v......no.II goes to the compressor, via the max/min pressure switch.
With the A/C control unit disconnected, and the car running, I jumped nos. III and II, to get a direct 12v to the compressor.....it did NOT kick in, hence, my thought was that the pressure switch was bad, preventing current to the compressor. I then left the above hook-up, and jumped the pressure switch, as which time the compressor did kick in, but no cold air.....of course, the control unit was out, and may have had a bearing.
There was infinite resistance between the two wires coming out of the pressure switch.....In the 88TR the high and low pressure are apparently read with only this one switch. This reading was the same with, or without the compressor engaged. Could this mean a bad pressure switch?
Could it be this simple? If the compressor was engaged, with fans going and engine running, shouldn't I have gotten cold air from the vents?...I did not!
If someone could lift the front hood and take an ohm reading on their pressure switch I would appreciate it. There is a quick disconnect next to it, and very easy to do.
BTW: The part number of the A/C control unit is: Bosch 1 147 328 034. Could this be a generic "cheap" part from another car?
The bottom line......is it the pressure switch, which would be likely if someone comes up with ohm reading of above zero. Or is it the control module....since with the compressor on I still got no cold air?...of course, the control unit was out of the car. |
Steve Magnusson (91tr)
Member
Username: 91tr
Post Number: 937
Registered: 1-2001
| | Posted on Friday, August 16, 2002 - 10:27 pm: | |
Thanks for the kind words Henry. I've looked at the TR AC system(s) fairly closely and have even added an auxillary DPDT (center off) switch in my TR so I can have vent, vent with blower, or full (stock) AC operation. I'm hoping to someday make some time and submit a short article on the subject to the FML (since every new TR owner is shocked there's no simple fresh air vent), but I keep putting it off.
I can't exactly recall the mounting/shape of the AC ECU, but you've got the right idea. It's got a 4-pin connector and a 6-pin connector, but both have enough wire so you can bring it out from behind the fusepanel yet still leave it plugged in. Let us know what you find out. |
Henryk (Henryk)
Junior Member
Username: Henryk
Post Number: 166
Registered: 8-2001
| | Posted on Friday, August 16, 2002 - 10:08 pm: | |
Steve: You REALLY know your stuff!!!!!
If the ECU is behind the fuse panel, then I must detach it, without removing any wires, and move it forward.....is this correct?
Thanks. |
Steve Magnusson (91tr)
Member
Username: 91tr
Post Number: 934
Registered: 1-2001
| | Posted on Friday, August 16, 2002 - 8:44 pm: | |
Henry -- If your blower system is working OK and the air comes out the proper vents (depending on what button is pushed) then I think you've got a good chance that the stuff in the center console is OK. When you push an AC button down three things happen:
1. the vacuum source is directed to the various actuators to open/close the various flaps (depending on the mode selected),
2. the blower system is grounded (to activate it), and
3. a ground signal is also sent to relay "lower case c" on the AC unit itself which closes and then sends a +12V signal to the AC ECU (to activate it) on Pin I which is the single green/white wire in the 4-pin connector coming in to the AC ECU.
If #1 and #2 seem to be working OK, I'd suspect the AC ECU is bad or the signals coming in (or rather not coming in) to the AC ECU. To test #3, with the motor running, press a button and see if the green/white wire on the 4-pin AC ECU connector goes +12V -- if it does you know the pushbutton switch is OK and the problem is elsewhere; if not, you've found the problem area (pushbutton switch, relay "c", or the wiring). You can also check that Pin III (three brown wires on the 4-pin connector) is always +12V with the key on. Anyway just thought I'd suggest this alternate method to check the pushbutton switch via the AC ECU 4-pin connector since it's a little easier to access (behind the fusepanel) than the center console (and no risk of leather damage).
PS The separate condensor fan on TRs only comes on when a thermo-switch measuring the temperature of the refrigerant tube exiting the condensor closes (i.e., the refrigerant is hot). If you've got some other problem preventing the AC system from actually coming on the condensor fan will not (and should not) run (unlike 308s). |
Henryk (Henryk)
Junior Member
Username: Henryk
Post Number: 165
Registered: 8-2001
| | Posted on Friday, August 16, 2002 - 7:41 pm: | |
Scott: The fans work fine, in all 3 speeds. Where is the AC fan housing...I'm confused! From my understanding, these fans work for A/C and/or heat.
It is not the rheostat that I want to check. It is one of the 3 round buttons, that are grouped together....the ones behind the OFF switch which turns all the vents off. The first round button is for the A/C, then one for the heat, and finally for the defroster. I am assuming that the one for the A/C basically turns on the unit (compressor). Nothing happens when I turn it on. Shouldn't there be a radiator fan that also starts up whenever the A/C is turned on..if so, do you know which one it is?
Thanks
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Scott Grossman (Sngsmgaolcom)
Junior Member
Username: Sngsmgaolcom
Post Number: 72
Registered: 2-2002
| | Posted on Friday, August 16, 2002 - 6:31 pm: | |
Henry,
It's usually not the fan rehostat that fries, its the power transistor mounted on the AC fan housing.
The easiest way to check is to turn the fan speed control all the way on, and if the blower motor comes on its the power transistor. Basically what you have is off and full on, with no inbetween.
I speak from experience (had 2 of these little gems go out on me within the course of a couple of weeks).
HTH
Scott |
Henryk (Henryk)
Junior Member
Username: Henryk
Post Number: 164
Registered: 8-2001
| | Posted on Friday, August 16, 2002 - 5:01 pm: | |
Thanks guys: I have checked the connectors and there is no discoloration noted. I removed the white strips and all contacts appear normal.......except those of the fuel pumps, which I repaired 2 years ago.....ended up buying a new panel at that time.
BTW: From what my experience, these white strips are NO longer available. I ended up soldering new clips onto the fuel pump wires and connecting them directly to the panel.....still holding with no problem.
So, my next step is to check the main A/C switch.
Thanks again. |
Steve Magnusson (91tr)
Member
Username: 91tr
Post Number: 931
Registered: 1-2001
| | Posted on Friday, August 16, 2002 - 4:32 pm: | |
Henry -- the jpeg in this thread shows the TR AC power socket/pin in the white connectors that Michael mentioned can get frazzled:
http://server.ferrarichat.com/~ferrari/ferrarichat.com/discus/messages/112/76486.html |
Michael N. (Man90tr)
Member
Username: Man90tr
Post Number: 626
Registered: 4-2001
| | Posted on Friday, August 16, 2002 - 4:22 pm: | |
Henryk, did you pull the white strips on the fuse panel to see if you have a bad clip connection? If you see any brown or black connectors then thats the problem. Same thing happened to me (twice) and both times it was the white strips on the fuse box that was the problem. I would check those before pulling the center console.
Michael |
Henryk (Henryk)
Junior Member
Username: Henryk
Post Number: 163
Registered: 8-2001
| | Posted on Friday, August 16, 2002 - 3:50 pm: | |
My A/C just stopped.......I suspect it to be electrical....fuse and relay are OK. I want to check the A/C ON/OFF switch, located in the flat panel, on the center console. It appears that the panel may just lift off, but I don't want to take any chances. The switch is the round one.
Has anyone ever done this before?
Thanks. |
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