Here's the deal: If I can't fix it you don't pay for it, other than return shipping for items you have sent me (assuming you want them back). (Be aware that you may lose the 'core' value of items such as cruise control amplifiers, as most commercial repair houses will not accept units that have been tampered with.) I can also do the on-car removal and reinstallation for local vehicles, though I'll charge for that time. The warrantee is 30 days.
Particular items I do (and do not) repair:
* Parts extra. Return shipping extra. (The parts are either cheap, or unobtainable. Luckily, mostly the former.) |
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Item | Years | Ailment |
| Mechanical clock | 68–early 70's | Gummy; blown internal fuse |
| Quartz clock, humming variety | mid-70's | Broken plastic axle pin |
| Quartz clock, ticking variety | late 70's and up | Bad capacitors |
| Cruise control amplifier, Philco/Ford | 75 | — |
| Cruise control amplifier, VDO | 76–89 | Bad solder joints; blown driver transistors |
| ACC pushbutton array, Chrysler | 77–80 | Bad servo unit—bad design! |
| ACC pushbutton array, VDO, 107/123/early 126 | 81–89 | Bad solder joints |
| ACC w/pushbutton array, 124/201/late 126 | 84–89 | Bad solder joints |
| Klima (AC compressor) relay | 84+ | Bad solder joints |
| Flickering Low Oil light | 84+ | Bad solder joints |
USPS (any grade) and UPS are the two preferred shipping methods. I usually return ship via USPS, because that is most convenient for me. We're in the 99016 Zip code (for shipping estimation). Unless you're in a screaming hurry, it's hard to beat the economy of USPS Parcel Post.
The more-expensive-to-repair ACC panel (because it contains the brain too) in the late 126 can be recognized as having a full-sized black "AUTO" blower button. The less-expensive-to-repair unit that is only a switch array has a narrow translucent "AUTO" button. I believe the 126 is the only model that had both types during its production run, and that the cutover was in 1986.
Engines with a separate AC belt may also have a Klima, but perhaps without a belt safety circuit. More caveats:
All that said, plenty of Klimas have indeed failed internally, preventing the AC from running. The easiest and best test is to temporarily swap it with a known good one, but for most people this is not an option. If you're handy with a multimeter you can follow this electrical checklist to see that Klima's getting what it needs from the rest of the car, and if it all checks out then it's almost certain that Klima itself is at fault. Obviously swapping in a known good Klima is a lot faster.
107/114/115/116/123/124/126 | 201 |
| Hanging from brake pedal support; Possibly attached to under-dash panel on stickshift models. | Under passenger floorboard. |
107 | 126 | 124/201 |
| Behind glove box. (Above small relays on firewall.) | Next to fuse box. | Behind battery. |
107/116/123/124/126/201 | 114/115 |
| Remove instrument cluster. Remove screws retaining clock or clock/tachometer assembly and carefully remove it from the cluster. The speedometer may need to be temporarily removed first if it's in the way. | Pull out instrument cluster. Unscrew two nuts holding in clock and pull it out from the cluster. |
The car is perfectly usable without the clock and/or tachometer. The 114/115 clock is a well-protected assembly that requires no particular care to ship. The others all have exposed hands that will require a little more care to ship safely. Please be careful, I can't do much about ruined cosmetics such as scratched faces or broken hands!
If operating on the instrument cluster is daunting you can of course send the whole thing in. Naturally shipping will be more difficult and expensive, and the car will not be driveable in the interim. Don't do this for the 114/115 cars, the clock comes out trivially and most (if not all) engine temperature gauges are mechanical, not electrical, and are very difficult to remove from the car. They are delicate, and expensive.
107/114/115/116/123/124/126 | 201 |
| Remove driver's under-dash panel, remove single 10mm bolt that holds the bracket carrying the amplifier to the brake pedal support, unscrew amplifier from bracket. Some stickshift cars have the amplifier attached to the under-dash panel itself. | Pull up passenger floorboard panel, unscrew amplifier from panel. |
The car is perfectly usable without the cruise control amplifier. Just remove it and send it in, preferably without extra metal bracketry or items hanging therefrom. It's an aluminum box the size of a paperback book with ten or fourteen pins coming out of it. The newest ones also have a little customization module plugged in to them, leave those attached to the amplifier!
107/123/126 | 124 | 201 |
| Remove ashtray and then the trim panel. Unscrew control panel and unplug it. If applicable, you'll have to pull the light string (like Christmas lights) out of its retaining clips. | Remove wood trim (2 screws above stereo). Remove 6 screws (2 sizes) holding ACC panel, etc. in. Pull panel straight out. Unplug it. | Remove ashtray and then the trim panel. Pull down two retaining clips at rear while pushing the control box forward. Unplug it. |
The car is probably not usable without the control panel as the system will default to pumping heat out the defroster ducts.
107 | 126 | 124/201 |
| Remove glove box liner. | Open hood. Look next to fuse box. | Remove flimsy panel behind the battery. |
Just unplug it and send it in. The car is perfectly usable without the Klima, though the transmission kickdown function may be disabled and of course AC will be disabled.
If operating on the instrument cluster is daunting you can of course send the whole thing in. Naturally shipping will be more expensive.
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The (12-pin) connector that plugs into the (10-pin) vacuum unit
amplifier looks something like this (facing the little sockets):
The first series of tests is done with the key off. The resistance between Pins 7 and 3 should be approximately 12 ohms and there should be no continuity to power or ground. If it's substantially more than this the actuator under the hood is broken, it's unplugged, its connector is extremely dirty, or the wiring to it is broken. Find out what's wrong and correct it. Pin 12 should be grounded, a resistance test of it to the car's chassis should show little/no resistance. (Leave the ground lead of the meter in this socket for the next series of tests.) The next series of tests is done with the key on (though the engine need not be running). Pin 5 is power, it should register +12 volts. (Battery voltage, that is, the exact value will vary with the circumstances.) Pin 6 is the brake lights, it should register 0 V normally, and +12 volts when the brakes are applied. Pin 8 should register +12 V unless the stalk switch is moved to Cancel. Pin 10 should register +12 V when the stalk switch is moved to Resume. Pin 9 should register +12 V when the stalk switch is moved to Accel. Pin 4 should register +12 V when the stalk switch is moved to Decel. The next test is done with the engine running. Connect one jumper between pins 6 and 7, and another between pins 9 and 3. When the Accel switch is activated the engine should rev up; releasing the switch or pressing the brakes should return the engine to idle. Be particularly careful on gasoline cars as there is no governor to prevent the engine from over-revving. If this doesn't work check the vacuum supply to the actuator, or its mechanical linkage to the throttle before suspecting the servo itself, it seems to be pretty reliable. The last tests are done while driving the car. Pin 11 is the signal from the speedometer, an AC voltmeter between it and ground (pin 12) should show a voltage that rises with speed. (And if your meter also measures frequency, like mine does, it certainly should show a rise in frequency with speed; frequency, in fact, is what the circuit is actually reacting to.) An inadequate supply of vacuum can cause strange problems with sinking set speeds, surging, etc. If this is your problem tee a vacuum gauge (a common vacuum/fuel pressure gauge or a MityVac will do nicely) into the black/yellow line that feeds the actuator, as close to the actuator as you can make it, and place the gauge where you can see it safely while driving. (A long hose can be used to snake the gauge into the passenger compartment, or you could try strapping the gauge to the wipers.) Try to use the cruise control normally. If the vacuum supply drops below 5" (Hg) during operation the cruise control cannot work properly: the value should normally be twice this number in operation. A low vacuum supply can be caused by leaks or occlusions in the piping feeding the actuator, and must be corrected before suspecting electrical problems. (A bad diesel vacuum pump will usually also exhibit problems with other vacuum-driven systems such as brake boost, ACC HVAC flaps, door locks, or even the ability to shut off the car with the key.) Of note is that the cruise system consumes the most vacuum while holding a set speed, not while accelerating, so the ability of the system to accelerate well does not prove that the vacuum supply is good. |
The connector that plugs into the servomotor unit amplifier looks
something like this (facing the little sockets):
The first series of tests is done with the key off. Pins 12 and 14 should be grounded, a resistance test of them to the car's chassis should show little/no resistance. The servomotor's clutch unfortunately has a series diode, so its resistance is difficult to measure. You can either connect an ammeter between Pins 1 and 5 and see approximately 300 mA, or you can defer testing it to a later step. (If it's broken the feedback resistance test will fail.) If you have a diode test range on your meter you can test it as a diode, though you won't see the actual resistance of the clutch coil. The resistance between Pins 7 and 10 (the motor) should be approximately 5 ohms, and there should be no continuity to power or ground. The resistance between Pins 9 and 14 should be approximately 3000 ohms, as should be the value between Pins 13 and 14, and likewise there should be no continuity to power or ground. If any value is substantially more than specified the actuator under the hood is broken, it's unplugged, its connector is extremely dirty, or the wiring to it is broken. Find out what's wrong and correct it. The next series of tests is done with the key on (though the engine need not be running) and the ground lead of the meter in Pin 12. Pin 1 is power, it should register +12 volts. (Battery voltage, that is, the exact value will vary with the circumstances.) Pin 8 is the brake lights, it should register 0 V normally, and +12 volts when the brakes are applied. Pin 3 should register +12 V unless the stalk switch is moved to Cancel. Pin 6 should register +12 V when the stalk switch is moved to Resume. Pin 4 should register +12 V when the stalk switch is moved to Accel. Pin 2 should register +12 V when the stalk switch is moved to Decel. The next test is done with the key on and the engine definitely not running. Connect one jumper between pins 5 and 3, another between pins 8 and 10, and another between pins 7 and 4. The ohmmeter should be connected between pins 13 and 14. When the Accel switch is activated the measured resistance should decrease smoothly to zero. Moving the switch to Cancel or pressing the brakes should return the resistance to the approximately 3000 ohms value. Repeat this test several times, especially trying to 'tease' it slowly. If the resistance jumps to a large value at any time the actuator itself has suffered internal damage to its feedback potentiometer, usually due to wear. I have heard of this being repaired by painting conductive substances on the damaged resistance track, but I have never done so. Procuring another actuator (used?) may be the best option at this point. Next start the engine, leaving the preceding three jumpers in place. When the Accel switch is activated the engine should rev up; moving the switch to Cancel or pressing the brakes should return the engine to idle. Be particularly careful on gasoline cars as there is no governor to prevent the engine from over-revving. If this doesn't work check the actuator and its mechanical linkage to the throttle. The last test is done while driving the car. Pin 11 is the signal from the speedometer, an AC voltmeter between it and ground (pin 12) should show a voltage that rises with speed. (And if your meter also measures frequency, like mine does, it certainly should show a rise in frequency with speed; frequency, in fact, is what the circuit is actually reacting to.) |
If your car passes all these tests and the cruise control still doesn't work right, then the amplifier is definitely at fault. Send it in! (If you wish to read about some of my personal trials with these systems, refer to here and the 240D's log starting here for about two weeks for the vacuum system; refer to here and the 380 SL's log starting here for the servomotor system.)
The connectors that plug into the late-model 126 and 124 cars' ACC panel look something like this (facing the little sockets):
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The connectors that plug into the 201 ACC panel look something like this (facing the little sockets):
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This checklist is only for the late-model 126 and 124 cars. (These are the ones with the black AUTO blower switch, where the control panel contains the entire ACC system. This is not true of the earlier panels that have the narrow translucent AUTO blower switch, see below for its test procedure.) If any of the sensor inputs are incorrect the ACC system will not be able to work correctly. For example, if the evaporator temperature sensor lies and indicates that the evaporator is freezing, the ACC system will shut off the AC compressor. So, a quick check of the inputs to the ACC system is in order: First connect your multimeter's ground lead to the right-hand connector's (X2's) pin 12, then measure the resistance to chassis ground. It should be extremely low. Next switch the meter to DC volts and measure the voltage at X1 pin 13 with the key on, it should read battery voltage. If this all passes, the system is getting good power and ground. Next measure the resistance to Sensor Ground (X2 pin 10) of the five temperature sensors (X2 pins 9, 8, 7, 4, and 2). For best results this test should be done in the morning after the car has sat in a garage all night, because this will allow temperatures to equalize. (It's difficult to know what the temperatures ought to be otherwise.) Compare the readings to these tables:
Next we'll check some of the outputs. The vacuum flap valves, X1 pins 1–6 & 8, should all measure 50–80 ohms to power (X1 pin 13). The Monovalve, X1 pin 9, should measure 11–19 ohms to power. Depending upon the system, a too-heavy load on any of these could cause the ACC system to shut itself down in order to protect itself. Next, the auxiliary coolant pump, X1 pin 10, should draw only about 0.8 A when power is drawn from it. This can be a bit of a tricky test, because the easy method of directly using a multimeter's 10 A scale can result in blowing the meter's fuse if the pump is seized, an all-too-common occurrence. A better, though more tedious, method involves a 21 W (2 A) brake lamp. Using jumpers you tie X2 pin 12 (ground) to the lamp, and the other pin of the lamp to X1 pin 10. If the lamp does not light brilliantly then it's safe to use the current meter between X2-12 and X1-10. When powered, you also should be able to hear/feel the motor running. The blower can be tested by feeding power (X1 pin 13) to X1 pin 12, the blower fan should run on high. Finally, the AC compressor output can be tested. X1 pin 7 may be grounded by a jumper (X2 pin 12 is handy) to force the compressor on when the engine is running. This should not be done for long, as the mechanism to prevent the evaporator from icing up will not be operating. The evaporator temperature can be watched via X2 pin 4, once it reaches the freezing point you shouldn't let it run more than another minute or so. If the compressor doesn't start you may have a Klima relay problem, a problem with the refrigerant pressure switch (or insufficient refrigerant), or a bad AC compressor clutch. |
This checklist is only for the 201 cars.
A significant change occurred in 1985, where the heavy current drivers of the ACC system (particularly the auxiliary coolant pump) changed from sourcing to sinking current. As a result, pin Xj-9 changed from power ('84) to ground ('85+), and the control panels are not interchangeable. If any of the sensor inputs are incorrect, the ACC system will not be able to work correctly. For example, if the evaporator temperature sensor lies and indicates that the evaporator is freezing, the ACC system will shut off the AC compressor. So, a quick check of the inputs to the ACC system is in order: First connect your multimeter's ground lead to the right-hand connector's (Xj's) pin 12, then measure the resistance to chassis ground. It should be extremely low. In '85+ cars, pin 9 should also be grounded. Next switch the meter to DC volts and measure the voltage at pin 10 with the key on, it should read battery voltage. In '85+ cars, you should definitely measure power on pin 9 as well. (I haven't tried it, but pin 10 might not be powered on '84 cars, as it might get power through the [missing] ACC module.) If this all passes, the system is getting good power and ground. Next measure the resistance to ground of the three temperature sensors (Xh pins 10, 9, and 7). For best results this test should be done in the morning after the car has sat in a garage all night, because this will allow temperatures to equalize. (It's difficult to know what the temperatures ought to be otherwise.) Compare the readings to this table:
Next we'll check some of the outputs. The vacuum flap valves, Xh pins 1, 2 & 4, and Xj pins 6, 5, 3, 2, and 1 should all measure 60–70 ohms to ground. Depending upon the system, a too-heavy load on any of these could cause the ACC system to shut itself down in order to protect itself. Next, the auxiliary coolant pump, Xj pin 7, should draw only about 0.8 A when power is drawn from (or fed to) it. This can be a bit of a tricky test, because the easy method of directly using a multimeter's 10 A scale can result in blowing the meter's fuse if the pump is seized, an all-too-common occurrence. A better, though more tedious, method involves a 21 W (2 A) brake lamp. Using jumpers you tie Xj pin 9 (power or ground) to the lamp, and from the lamp to Xj pin 7. If the lamp does not light brilliantly then it's safe to use the current meter directly between Xj-9 and Xj-7. When powered, you also should be able to hear/feel the motor running. (The key has to be on for this test.) The blower can be tested by feeding power (Xj pin 10) to Xj pin 8, the blower fan should run on high. Feed power to Xj pin 4, the blower fan should run on low. Finally, the AC compressor output can be tested. Xh pin 6 may be grounded by a jumper (Xj pin 12 is handy) to force the compressor on when the engine is running. This should not be done for long, as the mechanism to prevent the evaporator from icing up will not be operating. The evaporator temperature can be watched via the resistance to ground of Xh pin 7, once it reaches the freezing point you shouldn't let it run more than another minute or so. If the compressor doesn't start you may have a Klima relay problem, a problem with the refrigerant pressure switch (or insufficient refrigerant), or a bad AC compressor clutch. |
The connectors that plug into the early-model 126 and late-model 107/123 cars' ACC panel, the ones that have the narrow translucent AUTO blower switch, look something like this (facing the little sockets):
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Before beginning testing of the car's components you can use the multimeter's resistance function to do some quick checking of the pushbutton array itself. This is not definitive, but if it fails these it's definitely bad. With the Normal (center) button depressed, measure the resistance between the right-hand connector's (X1's) pin 11 and the left-hand connector's (X2's) pin 10. It should be very low, and should be constant even with flexing and tapping on the connector pins. Similarly, there should be continuity between X2 pin 12 and X1 pin 6. With the OFF button depressed, there should be continuity between X1 pin 4 and X1 pin 3.
For testing the car's components, first connect your multimeter's ground lead to the right-hand connector's (X1's) pin 3, then measure the resistance to chassis ground. It should be extremely low. Next measure the resistance to X2 pin 2, it should also be extremely low. Next switch the meter to DC volts and measure the voltage at X2 pin 12 with the key on, it should read battery voltage. If this all passes, the system is getting good power and ground.
| °C | Cabin X1-2 | Lockout X2-9 |
|---|---|---|
| 15 | 15.7 | ∞ |
| 25 | 10.0 | ∞ |
| 35 | 6.5 | 0 |
| 60 | 2.5 | 0 |
| 80 | 1.5 | 0 |
Unfortunately the temperature controller is also wired to this pin at this time, so the reading will not match the table, it will be lower. I measured about 7.5 kΩ on a 60 °F morning. To get readings that match the table you can unplug the temperature regulator, usually buried deeply behind the glove box, but that may not be particularly easy to do.
Next we check the cold engine lockout switch. When the engine is
warmer than about 100 °F the resistance between X2 pin 9 and
ground should be very low, otherwise it should be very high.
Next we'll check some of the outputs. The vacuum flap valves, X1 pins 7 & 10, and X2 pin 11, should all measure 35–80 ohms to ground (X1 pin 3). One additional flap valve is referenced to power, the resistance betwen X2 pin 7 and X2 pin 12 should also be in this range. The Monovalve, X1 pin 4, should measure 11–19 ohms to power (X2 pin 12). Depending upon the system, a too-heavy load on any of these could cause the ACC system to malfunction.
Next, the auxiliary coolant pump, X2 pin 10, should draw only about 0.8 A when power is fed to it. This can be a bit of a tricky test, because the easy method of directly using a multimeter's 10 A scale can result in blowing the meter's fuse if the pump is seized, an all-too-common occurrence. A better, though more tedious, method involves a 21 W (2 A) brake lamp. Using jumpers you tie X2 pin 12 (power) to the lamp, and from the lamp to X2 pin 10. If the lamp does not light brilliantly then it's safe to use the current meter between X2-12 and X2-10. When powered, you also should be able to hear/feel the motor running.
The blower can be tested by feeding power (X2 pin 12) to X1 pin 12 and grounding X2 pin 8, the blower fan should run on high.
Finally, the AC compressor output can be tested. X1 pin 6 may be fed power by a jumper (X2 pin 12 is handy) to force the compressor on when the engine is running. If it doesn't go on you may have a Klima relay problem, a problem with the refrigerant pressure switch (or insufficient refrigerant), or a bad AC compressor clutch.
If you get all through this and there are no failures and the system's symptoms (as described above) indicate that the ACC control panel is possibly to blame, then it probably is at fault. Send it in!
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This checklist is specifically for a 300 SDL, with a Klima labeled "D-Klima Kickdown", but other cars are similar.
If you get all through this and there are no smoking guns, then the Klima is probably at fault. Send it in!
Oh, and the official test of the Klima's serpentine belt-saver circuit is to slop some water on the compressor's clutch and belt when it is running, it should stop and stay stopped. (The water causes slipping which the Klima detects and reacts to.) Stopping and restarting the engine should result in normal operation again.
With the blower resistor pack disconnected you should be able to measure resistances between pins according to this table:
| Pins | Ω |
| 5–3 | 1.4 |
| 3–1 | 1.4 |
| 1–6 | 1 |
| 6–4 | 0.8 |
| 4–2 | 0.4 |
As all resistors are actually in series you should be able to measure the sum of the resistances between non-electrically-adjacent pins. For example, between pins 5–2 you should be able to measure 5Ω, the sum of all the resistances. There should be no continuity to ground. Because of the low values you may have difficulty accurately measuring these resistances with inexpensive test equipment. Fortunately the typical failure is an open circuit (rather than a change in bulk resistance of the coiled metal), and even the most pathetic excuse for an ohmmeter will show you that. (I'm not even sure a resistance change such as I describe is possible.) Also possible, though rare, is a full or partial physical short due to damage (overheating?) of the coils. This might be difficult to distinguish via inexpensive test equipment, but should be visible through the vent holes in the side of the resistor pack.
Non-automatic blower speed change systems (regardless of year) use some variation of the resistor pack along with a manual switch and the appropriate tests are similar, though the number of resistors and their values may not match the above.
For 1986 and beyond automatic blower speed variation is accomplished by an electronic regulator, colloquially called the 'porcupine' due to the large number of metal cooling spines on it. Currently I have no particular tests recorded for that, though it is testable.
Using a long wire clipped to the sender's wire (still disconnected from the sender), start the car and sit where you can see the low-oil light. The light should come on at about 60 seconds. If you ground the wire continuously for two seconds the light should go out. If you unground the wire again the light should come back on in 60 seconds. This behavior should be very consistent. If the light reacts instantly to the wire's state instead of exhibiting these delays the low-oil board is definitely bad. Send it in! (It's probably the solder joints in the oscillator circuit.)