348 View inside the Climate Control ECU - Info Request

It is (burnt) original. It is a resistor and should have "68RJ" written on it. On one of your pictures, it appears that the writing is still visible; can you read it?

If you confirm 68RJ, then it is 68 Ohm resistor of some 1-2 Watts. You can replace it with a standard resistor of the same Ohm value and similar size. However, it is possible that the resistor was overloaded and burnt by some other failed component, in which case the same will happen to the new resistor. After replacement of the resistor, connect the AC ECU briefly and, if it still does not work, disconnect it immediately. In that case, you will have to first check the power transistor next to the blown resistor.

 

It is a 0.82 Ohm resistor (it was nice green colour originally). So, look for a 0.82 Ohm resistor in radio shacks, at least 2W but better 5W since there is enough space to put in a bigger one. I suspect that the large transistor next to the blown resistor is controlling the heater pump (the highest load "consumer" for the AC ECU) so check whether your pump motor is good by connecting 12V directly to it. If the motor has failed (seized or has a short), it will probably not run but draw excessive current which could have been the reason for the resistor (and possibly the power transistor) overload ad damage. In fact, it is better to check the water pump motor first, then the large power transistor.

 

I wouldn't worry about the PTC, it looks good (never mid the chipped-off coating at the leg). I suggest that you, straight away get both, the resistor and the transistor. The transistor is TIP 142, easily available ("9144" does not count, just a batch number). This transistor is the same as the two power transistors inside the fan speed controller so it is good to have a few of these as spare. Once you have verified that the heater pump motor is good, install a new resistor and give the ECU a brief check, with the ECU connected but still out of the box (if possible?) and keep an eye (a finger) on the new resistor. If you see it gets very (burning) hot or starts smoking, disconnect the ECU and then go to the transistor.

 

It is original, I have one removed from my (now modified) AC ECU - same green colour as the longer resistor next to it. Your resistor is black because it was seriously burnt.

 

If I remember well, the SECI R82 (0.82 Ohm) resistor that I removed from my White-Black ECU is the one marked by the red line on the pic below. Otherwise, there are no part numbers for the resistor or the transistor. They are just a "0.82 Ohm" resistor and a "TIP142" transistor.

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I had a look at the circuit board (same as the pic above) removed from my AC ECU as well as at the wiring diagram. I can confirm that the transistor TIP 142 and the resistor R82 (0.82 Ohm) are the power circuit that controls the Electric Water Pump, via the Pin 14 of the ECU's yellow socket (2nd pic below). The internal AC ECU circuit (the transistor, 1st pic below) connects the negative terminal of the pump motor to the ground (the motor has ignition switched +12 volt on its positive terminal) thus switching the pump motor on. The motor current flows through the resistor (R82) and then through the transistor (TIP 142) to the ground. The R82 resistor is there to somewhat limit the current and protect the transistor.

So, if the R82 resistor is burnt, it means that there was overload by the pump motor. The code E5 you are getting means "Motor for heater valve control" but it may not be accurate. In addition to the burnt resistor, such overload current might have also damaged the transistor TIP 142. The checks should start with the pump motor (sized or has internal shorts in its windings thus drawing excessive current). With regard to the transistor, if you don't have the means to check it, just replace it (or replace it anyway). And a new resistor, of course.

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SECI before....
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...and after.
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Related info:

A good water pump motor draws 0.5 Amp when not loaded by pumping of fluid. It probably draws about 1-1.5 Amps when in the coolant circuit (I have no easy way to check as my pump is no longer in my 348). So, if it draws considerably higher amps (say about 3 Amps) when tested while still in the coolant circuit, the motor is either seized (stalled) or just bad.

 

Also check the diode next to the resistor.

 

You can probably test the diode in-situ when you also remove TIP142 as the anode of the diode appears to be connected only to the link from the SECI resistor to the collector of the transistor. If this is correct, you can test the diode on the pc board but I don't think there is any problem with it as it seems that it just conveys a small signal - the information on the voltage drop across the SECI resistor, to the small transistor near the diode. The small transistor is driving TIP142 (via its base) and the voltage drop monitoring should be a kind of overcurrent protection circuit for TIP142 - if the voltage drop across SECI is too large, it means too high current caused by the pump motor; the small transistor should then start reducing the current through TIP142 to prevent its overheating. However, it seems that in your case this did not help. There is probably a limit as to what overload current this circuit can compensate for. On the other hand, it is possible that the main culprit is actually failure of TIP142 which, if resulted in a short in it, left the water pump current flowing through the SECI resistor directly to the ground, thus resulting in the resistor burn-out. You will find out when you test the pump.

Otherwise, the solders of TIP142 do not really look as redone. I don't think any repairer would bother about the white line so it was probably drawn during manufacture.

 

Yes you can. Not for 100% but you are sure for 95% when it checks out ok.
As M already stated it is probably a protection diode for the TIP142 for reverse tension spikes coming from the waterpump. If the diode is SC the current will burn out the resistor. So do check the TIP and diode both.
And of course wiring and pump.

PS :Those solder joints look really bad.

Grts
Patrick

 

The legs may not have been cut, they have steps near the transistor body:

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