FBH The end of the SAGA ?

kokamagi · 10th February 2023, 09:33

Meanwhile I have taken out FBH and did some testing.
The common suspicious resistors were ok, but I had several resistors out of range (13 resistors in total), but not totally shorted or open. See attached pictures.
No bad solder joints found. I don't know if these values are enough to create problems.
I also did the component tests with WTT on the table (21W bulb in place of the fuel pump) and measured voltages on driver FETs legs. Pictures of scope patterns also attached.
Drain of all the FETs showed battery voltage at all times.
Source voltages were all 0 while components switched off (except circulation pump, which showed 2V, strange).
Gate voltages were all close to 0 (20...50mV) while components switched off (except circulation pump, which showed around 1.45V, again strange).

When components were turned on, the source voltages were as expected, only circulation pump did nothing. See pictures.
Gate Voltages had very high peaks, I don't know if it is normal or not. Gate voltages on Fan and Circ. pump FETs were around 200V and very noisy, big ripples. Again, don't know if it's normal or might be caused by some bad capacitors. It can be only seen with scope, the multimeter shows 16,5V at Fan FET's gate, 4,3V at FP FET's gate, and 14.5V at GP FET's gate while running.

I wanted to try the 21W bulb in place of circ. pump, but decided to try the old pump first. And it seemed to work perfectly, turned on and ran every time commanded.
With the working pump connected, but not running, The voltages were 0.94V on the source pin and 0.41V on the gate pin.

Another thing I noticed, is that there is no voltage drop on Circulation Pump's FET (between source and drain) while running, but for example on Fan's FET there is a drop of about 1.2V.

From this information is it possible that the CP FET itself is faulty?

PS.
Does anyone know how can I start FBH with WTT software from the "control" tab? It is greyed out for some reason.

Any thoughts?
Keijo

Pictures:

https://www.dropbox.com/s/j0uuj7vpmc...8__01.jpg?dl=0
https://www.dropbox.com/s/j0uuj7vpmc...8__01.jpg?dl=0
https://www.dropbox.com/s/3ax5bmn548...20Off.JPG?dl=0
https://www.dropbox.com/s/p8hsm08sgj...tered.JPG?dl=0
https://www.dropbox.com/s/2aq877k9to...20Fan.JPG?dl=0
https://www.dropbox.com/s/mqnu9cz1bj...0Pump.JPG?dl=0
https://www.dropbox.com/s/8ifdmg96yv...0Plug.JPG?dl=0

10th February 2023, 09:33	#11
kokamagi Newbie None at the moment Join Date: Nov 2022 Location: Viljandi Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts	Meanwhile I have taken out FBH and did some testing. The common suspicious resistors were ok, but I had several resistors out of range (13 resistors in total), but not totally shorted or open. See attached pictures. No bad solder joints found. I don't know if these values are enough to create problems. I also did the component tests with WTT on the table (21W bulb in place of the fuel pump) and measured voltages on driver FETs legs. Pictures of scope patterns also attached. Drain of all the FETs showed battery voltage at all times. Source voltages were all 0 while components switched off (except circulation pump, which showed 2V, strange). Gate voltages were all close to 0 (20...50mV) while components switched off (except circulation pump, which showed around 1.45V, again strange). When components were turned on, the source voltages were as expected, only circulation pump did nothing. See pictures. Gate Voltages had very high peaks, I don't know if it is normal or not. Gate voltages on Fan and Circ. pump FETs were around 200V and very noisy, big ripples. Again, don't know if it's normal or might be caused by some bad capacitors. It can be only seen with scope, the multimeter shows 16,5V at Fan FET's gate, 4,3V at FP FET's gate, and 14.5V at GP FET's gate while running. I wanted to try the 21W bulb in place of circ. pump, but decided to try the old pump first. And it seemed to work perfectly, turned on and ran every time commanded. With the working pump connected, but not running, The voltages were 0.94V on the source pin and 0.41V on the gate pin. Another thing I noticed, is that there is no voltage drop on Circulation Pump's FET (between source and drain) while running, but for example on Fan's FET there is a drop of about 1.2V. From this information is it possible that the CP FET itself is faulty? PS. Does anyone know how can I start FBH with WTT software from the "control" tab? It is greyed out for some reason. Any thoughts? Keijo Pictures: https://www.dropbox.com/s/j0uuj7vpmc...8__01.jpg?dl=0 https://www.dropbox.com/s/j0uuj7vpmc...8__01.jpg?dl=0 https://www.dropbox.com/s/3ax5bmn548...20Off.JPG?dl=0 https://www.dropbox.com/s/p8hsm08sgj...tered.JPG?dl=0 https://www.dropbox.com/s/2aq877k9to...20Fan.JPG?dl=0 https://www.dropbox.com/s/mqnu9cz1bj...0Pump.JPG?dl=0 https://www.dropbox.com/s/8ifdmg96yv...0Plug.JPG?dl=0