Low Coolant Alarm - How to fit one on the cheap.

I was checking all this out and was cautious after I noticed that some of float switches on ebay are only rated to 85 deg C. Some are OK at 125 deg C

Those farnell ones are rated to 125c

Um........I think I might just stick with my B&G unit!

Ben = tight
B&G = £100+
Davids kit = £40 max

I guess I look at it as doing it on the cheap has probably already cost you more than the purchase price of the B&G unit, what with the El-cheapo low water alarm that used self tapping screws as sensor elements, then of course there's all the Halfords pain and suffering with the hamburger induced headgasket failure!

It all comes down to what I constantly hammer into the heads of all the trainees, apprentices and proteges: :bat:
"Do it right and you should only do it the once.......but take shortcuts and do it wrong and you'll have to keep doing it time and time again until such time as you do it right!"
And: "Something that has a high purchase price and works properly is cheaper in the long run than something that has a low purchase price and doesn't work well!"

Naughty naughty! drilling holes in an expansion tank; the police are coming.

I didn't tell you that in my last TF I had this system installed for 10 months without any issue and David has had his for a lot longer than this. This is a miles better setup than the cheapo screw thing.

But yes officer... Guilty with expansion tank drilling as charged (oooooopssss)

I've built the one referenced in the photographed circuit diagram and it does wok, although I had replaced my expansion tank earlier as the old one split and the new one had the sensor built in. The relay part with the delay timer is useful as you can adjust the delay before the alarm goes off.

Total cost including wiring and more LED's than I'll ever use in my lifetime? A little short of £35 (The tank was £20 the rest components)

Ben states that the time from a low coolant alarm going off is critical, maybe 20 secs., before damage can occur. :hgf:
So fitting a delay into the system cuts the safety margin :yesnod:
So why buy a system that can give false alarms
My Lolarm 2 has never triggered in the 18 months since installation & yes it is working.

I've got a LoLarm too, have to say its pretty good although when I got back from a long run a while ago I did test it the next day and it didn't work ! Took the float out and wipe some gunk off it and all was ok again.

My fault should have tested it pre run, but it usually goes off over the big speed bumps near us so that performs as a test


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Brilliant. Followed your instructions virtually to the letter. although I hot glued the relay and buzzer to the centre console side panel (the bit with the foot well light) and followed the wiring loom down the passenger side. really neat job

I need some electrical assistance. Ihave replaced the expansion tank with an oem tank with float switch.
Due to a fracture of the lower hose joint on the tank caused by the metal insert having slipped down into the hose, meaning when I tightened the hose clamp, the plastic broke.

Now because the switch operates in the opposite way to the maplins float switch, ie normally open i moved the connection on the timer unit from the NC to the NO terminal. All good in that the alarm sounds when the float drops,
BUT the alarm sounds immediately and stays on for the delay time.

Obviously I need to change something but I'm unsure what.

I suspect that I may need to connect the float to a live feed rather than to earth,and perhaps move the trigger to the other trigger terminal.
However I dont want to fry the timer module by guessing wrong.


Could someone with the requisite knowledge steer me right please?