Trailblazer/Envoy Thermostat

lovely job to do you are ment to remove the whole rear end complete with engine/gearbox . but you can do it by removing the rear suspension arms/ drive shafts and moving the gearbox into the subframe and work through the space between engine/gearbox, its tight but can be done

Suggest disconnecting water supply / inlet & outlet. Drain tank using garden type valve located at bottom of tank. Rotate tank for better element access.

It's almost certainly the horn its self. It's not a very common fault, but it's not unheard of. I would suggest testing the horn directly by running a pair of wires from the battery directly to the terminals on the horn. If it still fails to work then the fault is proven to be a defective horn.

Some hornd have an adjustment nut in the centre (Depending if it's a diaphram type horn or a "snail shell" design). If you have proven that the horn is at fault, there's no harm in having a fiddle with any adjustment nut you can find to see if it helps. Experience shows that, as a general rule, once they start playing up, a replacement is usually the best action because they tend to fail again quite quickly.

Your local Auto factors will supply a generic horn that will do the job.

Are you in the UK? If so, Halfords stock the "Mountney Magnum Car Horn" and they are half price right now at £5

REMOVE HOTWIRE HORN OR PRESS REMOTE BUTTON LOCK CAR DOORS IF YOU HEAR CAR HORN BLOWS WHEN ACTIVATE CAR ALARM. HORN WORKING.MORE LIKELY THE AIRBAG AND HORN PAD NEED REPLACING.IF YOU GOING TO FIX. DISABLE AIRBAG IN THE STEERING WHEEL BEFORE REPLACING THE AIRBAG AND HORN PAD. TURN OFF RADIO.THEN DISCONNECT NEGATIVE BATTERY CABLE FOR 20 MINUTES BEFORE REMOVING AIRBAG IN STEERING WHEEL.THAT HORN PAD WITH AIRBAG IS NOT GOING TO BE CHEAP.

On most there is a hold that bolts to the bottom of the battery tray with a 12mm bolt. This hold is hard to tell apart from the battery itself - same material, same color.look down on the bottom for a triangle shaped tab that has a bolt in the center, loosen this bolt and she should come out.