[SOLVED] Red light flashes next to barrel-port

[FreeRangeRon]

From the schematic and data sheet, if thermistor is right,
between FB (14) and GRD (25) should be 2.1V, or 2.05 if a bit hot or 2.025 if  hot
And, obviously R53 should be roughly 10K, depending on temp, so 5-12K
GRD is not a pin, the foil under chip, any good grd will do I think (or pin 23)
pin diagram on pg 4 of datasheet

Thanks for the info wdt, i've made some measurements:

Voltage between FB (14) & GRD:
Battery: 1v
Battery & charger: 1.8v

These are not within the range you mentioned, do you think that's why the battery isn't charging? I'll need to look over the charging IC's datasheet again to understand this relationship for myself.

R53:
No Battery: 18.7K
Battery but no charger: 6.7K
Battery & charger: Out of Range

I also checked the resistance on the battery side, the reading between the thermistor (white lead) and ground seems to be bang on 10K so that looks fine. To be extra sure I connected the battery without the thermistor lead and replaced it was a 10K resistor. It didn't make any difference, I still got the red flashing LED, and the voltages across FB & GRD were the same.

When I was searching around I noticed that there was, what looked like, a short between pins 14 & 15 on the BQ24171:

Checking the datasheet it doesn't look like it should have caused any problems on the IC, the SRN pin is rated up to 20V but I don't know what other strange behaviour that could've been causing elsewhere in the circuit. I went ahead and fixed it anyway:

But, still red flashing light and no battery charging.

Perhaps the BQ24171 is damaged? Although I've tried a few things I don't think I've made much progress yet. Back to the datasheet tomorrow I think, where hopefully I'll have more luck.

Thanks in advanced for any further suggestions.