The other possibility is that it's a digital command signal of some kind. I don't know how they typically do that, but if a
0 is 0 volts and a 1 is 12V, for example, looking at it with a volt meter, you would see a range like that given. They do have that 16 pin chip there, doing something. It might receive the command and then output the appropriate PWM for rest of the circuit.
Well, that's about what you need to know. Game over.
--scott
Do you see the two groups of three empty holes on the right side? They look like cracked solder joints on TO-220 packages which could be semiconductors or power resistors.
You can see the leads in those holes, in this photo. They look cracked. That is a common failure due to stress caused by uneven heating of potted components.
Here's what the heatsink looks like when I cut into it today:
Ha, keep going!
Someone had scoped the whole board, and it was DC voltage everywhere (according to that reference). It's pretty clear there is no PWM.
The 16-pin surface mount chip seems to be a automotive temperature compensated voltage regulator with a huge voltage range, according to a lookup of the part number on it.
Here is the Elmos 10901D chip of my FSU as I cut it open today.
Like I said before, don't drive one then. It's kind of like going on a date with that unbelievably attractive female type who is also smart, witty, fun to be around, actually seems to like you, and oh by the way is completely mentally unhinged.
Suddenly you find yourself putting up with all sorts of stuff that you wouldn't, otherwise... (now that said, touch wood, current ride has exhibited none of the known issues... which reminds me, I need to call and schedule the battery cable recall @ the stealership)
nate
LOL. There's more truth to that then you may think.
On Tue, 26 Mar 2013 14:09:11 -0400, Michael A. Terrell wrote:
It might be, but this Russian site intimates it's a temperature compensated voltage controller.
Translation below: REGULATOR ELMOS 10901D Found: 100 Showing: 1 - 10 Car Voltage Regulator Category: Car Source: Radioland country Electronics Temperature controller cabin air KAMAZ Category: Car Source: Plans radiokonstruktsy Simple Temperature compensated voltage regulator. Controller together with thyristor-transistor electronic ignition unit with a long spark, ensuring the rapid start-ups at various operating conditions, allowed to increase battery life of up to nine years. Category: Car Source: For the life of a soldering iron ... Regulator for automotive windshield Category: Car Source: MASTER KIT The controller measures the wiper-this control is designed to use regular mode switch blades and is contactless. Category: Car Source: For the life of a soldering iron ... Temperature compensated voltage regulator device in some ways superior designs. The controller can be used as a universal device is suitable not only for mounting on any car, but everywhere, where the generator rotor speed is variable (eg, wind power). Choose the appropriate control elements, it can be easily adapted to work with any voltage (up to 400V) and excitation current (tens of amperes). Category: Car Source: For the life of a soldering iron ... Voltage regulator 2012.3702, 22.3702, 221.3702 Category: Car Source: For the life of a soldering iron ... Voltage regulator 201.3702 Category: Car Source: For the life of a soldering iron ... Voltage Regulator 13.3702 Category: Car Source: For the life of a soldering iron ... Voltage regulator RR132A, 1112.3702 Category: Car Source: For the life of a soldering iron ...
Are those the two transistors sitting on top?
It's an epoxy resin filled with silica. It will come off with DMSO at three atmospheres or so. Sometimes a soak in DMSO for a couple weeks will make it peel off. This will also soften the PC board though.
--scott
I feel your pain. I have a 1980 MB 300SD. For the AC, MB used a part from Chrysler that they used on the Imperial. It's the size of a grapefruit and it controls the entier HVAC system. In that one widget you have a valve that's in the path of the engine coolant system that goes to the heater, about a dozen vacuum hoses that control the various flaps. You also have the electical outputs for the blower, AC clutch, etc. And all that is driven by a small electric motor that is inside the thing. The motor is part of a feedback servo system that moves in relation to the desired temp setting vs the actual. It goes from max cooling, to max heating. Oh, and a critical part of that sytem is the potentiometer inside that widget, the resistance value of which changes based on the current position of the motor that works the whole thing, moving it from max cooling to max heat.
So, you have hot engine coolant, vacuum, electrical, a potentiometer, all inside one widget. How smart is that? The typical failure mechanism is that the plastic housing cracks and it leaks coolant. They were up to $600 in the 90s for a new one. Some guy down in TN started a business rebuilding them. His uses an aluminum housing for the part where the valve and hot coolant are. I bought one 10 years ago for $500. It's been fine until recently. Now it's starting to have problems. Haven't had a chance to find out what's wrong.
Well, I only had lunchtime, and it got uglier & uglier as I went!
Unless there is some chemical way to remove that black/gray rubbery (like a tough pencil eraser) gunk, there will be no way to read the numbers on the two transistors.
Actually, it's the same transistor, which broke in half while I was attempting to get the black rubber eraser stuff off of it to read the numbers.
It's really going to be HARD to read those numbers now...
Yes.
This quote below is verbatim from this location:
- the FSU works again
- there is no PWM , the gates signals are continuous voltage only , this is the reason why it heat so much its aluminium box... In fact there is no point on the board where square signals are present. Can somebody check its own FSU if it's the same ?
- the 2 bridges are in fact 2 resistors 10 milliohm used to balance the currents between the 2 MOSFET and balance the power also. The mesure of the DC voltage on those resistors can be used to evaluate the current of the blower and its worn state.
- I guess the principal duty of the computer on the other side is switching off the power transistors if the control voltage goes under 1V.
I put the FSU back in the car and it still work, I don't know if it will last long. because of the heat...
Olivier[/QUOTE]
I only found 1 transistor.
This is what is suggested in this quote below:
[QUOTE=540iman]There is only ONE mosfet in the FSU and I would forget about trying to replace it even if you had one. Also, we have no reason to believe the mosfet has caused any FSUs to fail. I have yet to see the resistors in any of the picture shown anywhere in this thread. Can someone circle the resistors for me? I would think they would be fairly decent wattage so they would be very easy to see, but I don't see any resistors.[/QUOTE]
Ok, they are most likely transistors and the two straps are combining the emitters. Is the center junction of the two straps connected to the motor?
Does the red jumper connect to the 40 amp fuse? If both of those are a yes, then they are most likely NPN power transistors and the jumper ties the collectors together. Or power darlingtons. And it is just a linear supply.
In your other pictures, the spring clips just hold the transistors against the heat sink.
I think he is incorrectly calling the SMT IC a mosfet.
What went in the other three holes on the PC board? What was under the two spring clips on the heat sink?
You said you tested the FSU alone. If so, how can you say there is no PWM signal between the car and FSU?
the gates signals are continuous voltage only , this is the reason why it heat so much its aluminium box... In fact there is no point on the board where square signals are present. Can somebody check its own FSU if it's the same ?
urrents between the 2 MOSFET and balance the power also. The mesure of the DC voltage on those resistors can be used to evaluate the current of the bl ower and its worn state.
Say what? 10 milliohms is .01 ohms. How could that possibly balance the power to a motor in a 40 amp circuit?
ng off the power transistors if the control voltage goes under 1V.
Which makes no sense at all.
last long. because of the heat...
It seems they last at least a few years. Maybe it's like gas. You buy it and you go so far. I think you're in way over your head here;
The main points of his post, like the "two bridges that are .01 ohm resistors, that "balance" the motor don't concern you in the least?
Blind leading the blind
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