LM393 comparator output does not attain 'high'

[earckens]

In the schematic attached, comparator LM393 (IC2A) does not attain more than 3.4V when driven high (Vcc = 18Vdc).

The output (pin 1) does turn to 0V when pin 3 voltage is lower than pin 2.
However, in the other case the output does not even attain 1/4 of Vcc.

How to remedy?

Edit: the output on pin 1 also serves as a sink for LED1. Which must turn on when pin 3 goes low, and turn off when pin 3 goes high.

 

[Diver300]

I guess that something is oscillating.

Does the LED light when it shouldn't?

 

[Nigel Goodwin]

A little positive feedback round the comparator might help?.

 

[earckens]

A little positive feedback round the comparator might help?.

Say 10k between pin 1 and pin 3?
But pin3 never exceeds +/-6V. Pin 1 would be stuck there?

Oscillation: I check on my scope this afternoon and feed back here.

 

[Nigel Goodwin]

Say 10k between pin 1 and pin 3?
But pin3 never exceeds +/-6V. Pin 1 would be stuck there?

Oscillation: I check on my scope this afternoon and feed back here.

I would suggest higher than that - try 100K or 1M and see if it makes any difference, if not try lower.