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Discussion Starter #1 (Edited)
87 Climate Control doesn't respond at all...

*note* edited title. It's not just the AC it's the whole climate control. No heat or AC. No blower, no compressor, nothing. The fuse is not blown.

The fuses look fine. I even switched a few around with no success. The light on the recirculation button doesn't come. I hear a quiet click when I turn the temp wheel all the way to 85 and over the "hump".

The engine is running when I tried these steps.

I'm not sure where to start from here. Any suggestions would be greatly appreciated.
 

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Did you searh on this forum for AC problems and fixes? As I recall there are some pretty good trouble shooting suggestions already posted.
Does your compressor engage? If not, your system may be low on refrigerant or have a more serious issue. Has the system been converted from R12 to R134?
 

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Discussion Starter #3 (Edited)
Nothing happens, at all. It's like you didn't even turn it on.

I did search, but didn't find anything that would help.
I've got a service manual comming but all it will do is show me how to get to things. I'm just trying to avoid buying random things to see if they work.

I don't know if it has been converted to R134. How do I tell?
 

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You have to start somewhere, lets start with the blower motor not coming on because it may be easy to distinguish between the blower motor/regulator not working, or the climate control unit not working or the ignition switch is not working.

There is a 3 terminal connector behind the driver side firewall, open the hood and it should be behind the brake booster. Disconnect this connector. Terminal 1, i.e towards the engine, is ground, check that it is so with a multimeter. The middle terminal should have battery voltage when you turn on the car. The third terminal is the blower control voltage. When you push the high speed switch on the climate control unit (car is running), and select the defrost position, you should get between approx 6 and 8 volts.

If you dont get battery voltage on the middle terminal when car is running, and if fuses are o.k. (fuse 12 in fuse box and there is another fuse outside the fuse box above the ignition control unit (near the driver side fender) - any one of the fuses should be o.k. for the test), you have a bad ignition switch or some cable in the switch has become loose.

If you dont get 6-8V on terminal 3, then the climate control unit is not sending the control voltage. This can either be because fuse 7 is blown or the CCU is bad.

If everything is fine on terminals 1, 2 and 3, then the blower motor or the blower regulator are bad, for this you will have to open the blower motor assembly.

Let us know what you find.

You can similarly test why compressor is not coming on. The CCU can only be tested superficially, nothing can be tested from the inside. On the otherhand, blower and compressor both not coming on can be a good indicator of a bad CCU. CCU controls the voltage to the blower motor regulator (terminal 3 above), and it also sends a signal to the Klima relay to turn on the compressor when the user selects a/c and the inside temperature is higher than the desired temp set by the wheel.
 

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Discussion Starter #5
THANK YOU Saumil,

I'm at work right now, but I'll give this a shot tonight.
 

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jones,

There is another fuse for the blower that isn't located inside the fuse box. It is a 30amp strip fuse that is mounted in a small, rectangular black plastic box. The small box is mounted on the inside left fender panel directly to the outside of the strut mount. It is hinged and rolls toward the motor.

Take a peek at this fuse.. I suspect it is toast. If so, they are inexpensive and purchased at the dealer or online. It would be best to make sure this is in order before we go any further with solutions for your problem.

Good Luck and keep us posted

Jayare
 

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Discussion Starter #9
Jayare,

That fuse is blown. I'm ordering one tonight. I hopeing that fixes it!!!
 

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That fuse is in parallel with fuse 12 in the fuse box, I never understood the purpose of such an arrangement unless one is a slow blow and another is a fast blow fuse. But if fuse 12 is o.k., your blower should still operate even if the other fuse is blown.
 

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Discussion Starter #11
Well, I may have more of a problem, but I won't know until this fuse arrives. I'll try to find a kit of fuses online somewhere.

OReilly auto parts has this fuse online.
 

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What I was trying to convey is that you dont have to wait for that fuse to test the blower circuit, if fuse 12 is fine in the fuse box, you should still be able to test the blower circuit while the fuse is ordered. Infact, you can even wire it for the time being.
 

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Discussion Starter #13
I am so dense some times. I hardwired it this morning and YES!!!! it works. Well, it blows air, I didn't have time to check for tempature change.

I have a new problem that I might start a new thread for. One (maybe two) of the loop return fuel hoses is leaking. It doesn't have a hole in it, looks like it needs to be pushed back on the nipple. I tried with some pliers but is there a better way?
 

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Huh !! Are you sure Fuse 12 is o.k. ? Or the circuit diagram is wrong. Anyway, this tells that the blower motor & regulator are o.k. Now if the air is not cold, need to check why compressor is not turning on. First check that there is adequate refriferant. If the refrigerant looks o.k., then you need to probe various terminals in the Klima relay's socket to determine why compressor is cut-off, could be faulty sensor signals, there are many that can cut off the compressor. The steps are as follows:


1. Turn Car Off
2. Pull Klima Relay Out
3. Put your multimeter on DC Volts setting
4. Connect the ground terminal of the meter (black color usually) to the battery's negative terminal
5. Connect the positive terminal of the meter to pin number 5 in the socket (Hopefully, you know which pin is 5)
6. You should get close to 12V, if not, the fuse is blown (#7 I think). Replace fuse. Put the Klima relay back in and check a/c again.
7. If the fuse is o.k. and the compressor clutch still does not run, then lets move on
8. Remove the Klima relay. Now connect the negative terminal of the meter to pin number 10 in the socket. (Hopefully you know which is pin 10). Put the positive terminal of the meter on the positive terminal of the battery.
9. Turn on the car and press one of the a/c switches on the push button unit.
10. You should get close to 12V when the a/c switch is on.
11. If you dont get close to 12V then there are one of two possibilities:
a. the push button unit is not sending the correct control signal
b. the pressure switch is not closed
For now, I am ignoring the trivial possibilities that wires or connectors may be broken. We can dive into these once we have some answers to the basic tests.
12. Turn the car off.
13. If you dont get the 12V, disconnect the two cables from the pressure sensor (should be at the drier), and jumper them.
14. Repeat steps 9 and 10.
15. If you still dont get the 12V, the push-button unit is not sending the signal.
16. Turn car off, dont keep the car running for a long time with the pressure switch cables jumpered.
17. If at step 14, you did get 12V, then the pressure switch is not closed
18. If the pressure switch is not closed there could be three possibilities:
a. refrigerant pressure is too low (lower than 2 bar)
b. refrigerant pressure is too high (higher than 30 bar)
c. the pressure switch is bad
you will need pressure gauges to seperate these possibilities.
16. If at step 11, if you did get 12V, then the push-button unit is sending the control signal and the pressure sensor is o.k. and we will move on.
17. If push-button unit is sending a signal and the pressure sensor is o.k. but the compressor clutch will still not run, then need to check the compressor clutch coil resistance.
18. Connect the positive terminal of the meter to pin number 7 in the socket and negative terminal of the meter to negative terminal of the battery.
19. Change the setting of the meter from volts to ohms.
20. You should get a low resistance about a few ohms.
21. If you don’t get a low resistance, need one last test.
22. Get to the compressor and disconnect the connector for the compressor clutch coil (there is a speed sensor cable that connects to the compressor connector also, you have to trace the clutch wire to the compressor connector to pick the right pin on the connector).
23. Put one of meter’s terminals on battery ground and the other terminal on the compressor’s clutch coil pin (polarity does not matter).
24. You should get a low resistance, about a few ohms. If you do get the low resistance at the compressor then compressor clutch coil is o.k.
25. If you get low resistance in step 23 but do not get a low resistance in steps 18-19, then the cable from the Klima relay to the compressor is bad, replace it.
25. If you don’t get a low resistance in step 23, then the compressor coil is open, normally this would require a new compressor.
26. If the compressor clutch coil is o.k. and the cable from the Klima relay to the compressor is o.k. then let us move on.
27. At this point, if the fuse is o.k., and the compressor coil’s resistance and cable are o.k., then jumper pin number 5 and 7 in the socket.
28. Turn on the car and your compressor should come on.
29. Turn car off
29. If the compressor does not come on, there are two possibilities:
a. the fuse is blown
b. the compressor has an internal mechanical problem, is likely seized.
30. No matter whether it is 29a (shorted coil) or 29b (seized), compressor is bad, replace it.
31. If the compressor comes on at step 28, but does not come on when the Klima relay is put back in and the push button switches are on a/c, then the Klima relay is not producing the 12V signal at its pin 7 to drive the compressor.
32. If Klima relay is not driving the compressor at step 31, then there are five possibilities:
a. the temperature sensor is bad
b. faulty throttle cutout microswitch (only for diesel automatic)
c. bad compressor speed sensor
d. bad engine speed sensor
e. bad Klima relay
33. Put the meter back on voltmeter setting. Do this test with engine cooler than 105 deg-C, better when just cold.
34. Put the positive terminal of the meter on the positive terminal of the battery. Put the negative terminal of the meter in pin 12 of the socket.
35. If you get about 12V, then the temperature sensor is bad. I am not sure about the physical location of this sensor but on my 87 260E, it is a 3 pin sensor on the engine I think third from last from the windshield side. You can ask your parts vendor about it.
36. If the temperature sensor is bad, then disconnect the sensor cables, put the Klima relay back, and try you’re a/c. If this was the only bad component, your compressor should start working. But again, don’t keep running like this, replace the sensor as soon as you can. If disconnecting the temp sensor cable does not work, there is still another problem. Remove the Klima relay and move on.
37. Put the positive terminal of the meter on the positive terminal of the battery. Put the negative terminal of the meter in pin 4 of the socket.
38. If you get about 12V, then the throttle cut-off switch is bad. This switch is supposed to be open and only close when the throttle is wide open. I am not sure about the physical location of this switch but you can ask your parts vendor about it. Once again, if you can find this part, you can disconnect the wire, put the Klima relay back and check a/c. If it still does not come on, then there is some other problem and move on.
39. Change the meter setting to measure resistance.
40. Put the positive terminal of the meter on pin 9 of the socket. Put the negative terminal of the meter in pin 11 of the socket.
41. You should get about 350 – 450 ohms. If you don’t get the low resistance but get very high resistance, either the compressor speed sensor is open circuit or the wire is broken somewhere. Do the same test as close as possible to the speed sensor (i.e. on the compressor connector) to rule out a broken wire. Replace sensor if it is bad.
41. If the resistance is o.k., then, jumper pins 5 and 7 on the socket.
42. Change the meter setting to ac volts.
43. Turn on the car.
42. You should get about 0.3V ac at idle of about 750 rpm. If you don’t get the ac voltage, and the resistance was kind of o.k., replace the sensor.
43. Turn off the car.
43. To check engine speed signal, put the meter setting to ac volts
44. Connect one terminal of the meter to pin 1 of the socket and the other to pin 2 of the socket.
45. Turn the car on.
46. For diesel: At idle of about 750 rpm, you should get a voltage greater than about 4V ac. And the voltage should increase with increase in RPM. For gasoline: at idle the voltage should be about 9V.
47. Stop the car
48. If you don’t get the voltage, switch the meter to resistance setting and readout the resistance between pins 1 and 2 of the socket.
49. You should get about 2 Kohms. If you get a very high resistance, check the resistance closer to the sensor to rule out a cut in the cable. Otherwise replace the sensor. Ask the parts person about its location.
50. If in step 15, you determine that the push-button unit is not sending the control signal, replace the push-button unit. This has happened to me once, the electronics driver inside the push-button unit is blown and it will not send the control signal to the Klima relay. What I did is bypassed the electronics and just used the mechanical switches to send the control signals. The downside is that there is no more auto modes, so when I feel like it is too cold, I would press the economy switch and I designated that switch to send a signal to cut-off the compressor. So my brain does what the box would otherwise do, have still not fixed the electronics, just a big headache to test this unit once it is out of the car. If you just bought a new one, you can ask for a replacement. Most likely the problem you are having is not in that unit.

This is awfully long and I may have missed some possibility, but you will have enough info to test this problem in a systematic manner and when you come to a point where you think something is missing, let us know, some one will help.
 

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Discussion Starter #16
WOW, Saumill...it would have taken me 5 hours to type that out!!! :)

These steps should keep me busy for a while.
I really appreciate the help.
 

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I have this in a word file and it is much easier to cut and paste everytime someone asks for it rather than point them to an old thread. I originally wrote this to explain it to someone who was at the same time learning to use a meter, and learning basics of electrical connections etc, so it can go very fast for someone who already knows the basics. Good-luck.
 

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jones,

There is another fuse for the blower that isn't located inside the fuse box. It is a 30amp strip fuse that is mounted in a small, rectangular black plastic box. The small box is mounted on the inside left fender panel directly to the outside of the strut mount. It is hinged and rolls toward the motor.

Take a peek at this fuse.. I suspect it is toast. If so, they are inexpensive and purchased at the dealer or online. It would be best to make sure this is in order before we go any further with solutions for your problem.

Good Luck and keep us posted

Jayare
Jayare - I suspect that I have the same issue. Is this the box that you're talking about (cover removed)? If so, I couldn't find a fuse. These seem to be connectors - not fuses. Your're advice is greatly appreciated.

Mike
 

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That is the strip fuse in the top of that box, but it looks new and clean,same with that red wire leading me to think someone alrdy did work to that part. Check regulator and blower motor itself.
 
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