C# Service

To simplify writing to a log file put the following code into a common class then you only need to add the line

common.writeToFile("your message"); in the places you want to log.

As to your other problem,
Where is Timer1 declared?  have you placed a timer compoent on a form or is it purly in code
have you tried to start timer just after the InitializeComponent

Timer t = new Timer();

public MyNewService()
        {
            InitializeComponent();
             t.Start();
            common.writeToFile("your message");
        }

//write to log file function -------------------------------
internal static void writeToFile(string outText)
  {
 
        string path = @"c:\logs\myservice\trace.txt"; // your path and file name

        // This text is added only once to the file.
        if (!File.Exists(path))
        {
            // Create a file to write to.
            outText += Environment.NewLine;
            File.WriteAllText(path, outText, Encoding.UTF8);
        }

        // This text is always added, making the file longer over time
        // if it is not deleted.
        outText += Environment.NewLine;
        File.AppendAllText(path, outText, Encoding.UTF8);
  }

Ahh thank you very much, my code now looks like this: is this what you meant?

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Linq;
using System.ServiceProcess;
using System.Text;
using System.IO;

namespace MyNewService
{
    public partial class MyNewService : ServiceBase
    {

       

        public MyNewService()
        {
            InitializeComponent();

            TextWriter tw = new StreamWriter("log.txt");                 
            tw.WriteLine(DateTime.Now + " COSHH Service has been installed correctly!");
            tw.Close();
        }

        protected override void OnStart(string[] args)
        {
            timer1.Start();
            TextWriter tw = new StreamWriter("log.txt");
            tw.WriteLine(DateTime.Now + " COSHH Service has started up");
            tw.Close();
           
        }

        protected override void OnStop()
        {
           timer1.Stop();
           TextWriter tw = new StreamWriter("log.txt");
           tw.WriteLine(DateTime.Now + " COSHH Service has stopped!");
           tw.Close();
          
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            TextWriter tw = new StreamWriter("log.txt");
            tw.WriteLine(DateTime.Now + " hello from COSHH Updater!");
            tw.Close();
           
        }
    }
}

However I'm finding that ONLY timer_tick fires now

Hi Matt.  The problem is that you are trying to write to a closed TextWriter.  You need to re-open the file, write to it, then close it. 

Debugging windows services can be a real pain.  It's very difficult to see what's happening internally, especially once you start adding multiple threads.  I add logging everywhere so I have a step by step record of what's going on.  I've also gotten in the habit of adding try/catch blocks to almost every section of my services.  In the catch blocks, I once again add logging so I can see what happened.  It takes a little more time to add all of the extra code, but it will save you tons of time in the long run.

Hope that helps!

Jeff