240 Coolant Level Sensor

[84B23F]

For around $10.00 (US) in parts (LED & Float), a cheap coolant level sensor can be created.

Stainless Steel Vertical Float - Ebay price around $6.00.

Green LED Pilot Light - Ebay price, around $5.00

On bottom side of coolant reservoir, I mounted the float. Between the top-edge of that center hole and that horizontal rib above it, I drilled out a hole in the center-line of those two points mentioned on bottom side with a drill press, via smaller drill bit first, then a larger sized bit. This is a top-side photo showing float.

I used a 4" side grinder on tank's bottom-mounting bracket so float's nut would seat within this bracket. When tightening nut, I used a hemostat (hemostatic clamp) to hold threaded part, and a wrench; once threaded part started to spin, I stopped tightening it.

One wire of float is hooked to a ground next to reservoir tank, and the other float wire goes thru firewall (where main wiring harness goes thru) and into vehicle's interior (inside, I fished wire across heater box), and hooked wire to ground side of LED light. For the positive wire, I hooked it to other side of LED, and ran this wire over to fuse box, and inserted it onto a fuse holder via alligator clamp.

Mounting LED - If mounted further inward on cluster, it will not seat flush, for LED I used.
It is mounted so when I'm driving at night, the steering wheel blocks this side light from my eyes; although dark nail polish could be used to block this side light. The cluster's night lights are not needed with LED mounted there. This 20ma draw LED is quite bright if pointed towards your eyes at night.

Operation - I have filled reservoir tank so when engine is cold, the LED will not be lit, except when anti-freeze solution is moving about. Once engine is warmed up, the LED stays lit most all of the time.

Footnote - Nothing fancy here, but I could have used a Bosch relay setup to set-off a buzzer. That float is good for a one amp draw, so using a 20ma LED does not overload it. Only with time will I be able to determine if an issue exist with float in tank; I have a spare tank in case there is an issue.

 

[Jack]

 

[nordmaschine]

So, you used normally closed switch float - when your coolant level drops, light goes out?

 

[84B23F]

when your coolant level drops, light goes out?

Correct...a fail-proof attribute.

Using a Bosch Relay, a person could have radio turn off, engine shut off, horn blow, or a light turn on or flash, but I wanted to keep it simple.


.

 

[nordmaschine]

Why not closed? It is usually easier to notice light going on suddenly, than going off...

 

[84B23F]

Why not closed?

YMMV...I live in a rural area where mice/rats can chew on a vehicle's wiring. By seeing the light flicker and when staying on, I know the circuit is working.

As I noted,

Operation - I have filled reservoir tank so when engine is cold, the LED will not be lit, except when anti-freeze solution is moving about. Once engine is warmed up, the LED stays lit most all of the time.

 

[84B23F]

It is usually easier to notice light going on suddenly, than going off...

If outbound side of fuel-pump fuse is used to power LED light, one can see if power is going to fuel pumps when starting vehicle, btw.

Footnotes:

1. Sensor's total length: 55 mm (straight sensor) (ebay ad calls it 55, but it may be 60 mm)

2. I'm going to try this on a 1993-940, which has a different tank. I will try a 55 mm first, and then a 75 mm one, if needed. If this upper mounted setup works, it will work in the opposite way so the light will light up when fluid level is low/empty.

3. Photo of 55 mm sensor

 

[84B23F]

Footnotes - It is possible to do this on a 940, but it requires using a drill press, drilling an outside hole in center of two ribs inside tank for sensor, and removing an inside wall, as shown in third picture down. When I finish up, I'll do a write-up, if there is an interest.

Drilling that hole must be centered between those inside ribs...I mean dead-center...as shown in last pic, vertical center-line is about 1-1/2"

This tank shown, if the OEM's float setup is still working can be used; it's just a ground circuit, like this float I installed. See this write-up. Here's some more info on this topic

For Volvo 940 with Rectangular Tank P/N 9142001/2." Volvo updated number, and current number I see for this tank is 9122997, along with required sensor, 3547710. Some $80.00 in OEM parts.

 

[84B23F]

when your coolant level drops, light goes out?

I removed LED light since it was too bright during night hours. I installed a 2" 52mm Tachometer , whose ground goes to that float, so that when water level drops, the tach goes out. It is also powered up via fuse #4, which tells me if fuel pumps are getting power.

This tach draws about 0.3 amps (300 milliamps), and that float can handle one amp.

So, for the tachometer and float, I have about $20.00 involved.