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I have searched the forum, reviewed the electrical schematics and do not understand how the coolant level sensor works.
Some background on this question:
I have a 1983 RX7 that I am converting to run in 24hrs of Lemons Races. Our team already has a 82 but it does not have the coolant level sensor installed. I am thinking that would like get one installed on the 83 BUT one of the prior owners cut / stripped the wiring harness out of the car but left it laying in the car.
Why am doing this?
I planning on setting up bright warning lights for oil temp and pressure, water temp as well as gauges to reduce the possibility of missing problem that destroys the engine and ruins the weekend.
The sensor i purchased from Mazda looks to be nylon with a single wire coming out of it so no ground path unless it via the coolant.
So what do some of you smart folks know about this?
The sensor works by being a ground when everything is OK. Zero resistance to ground. Anything other then ground (resistance) will illuminate the light. More resistance, brighter light. When one is not installed or bad, a trick to get the light out is to ground the wire on the harness side.
Last edited by KansasCityREPU; Jun 18, 2021 at 11:41 AM.
It's sensing the water level and taking to ohms to near zero or at zero. I doubt it's grounding. No relay needed. The sensor is just adding/removing resistance.
My concern would be water temp.
Last edited by KansasCityREPU; Jun 18, 2021 at 03:40 PM.
Its a lemons car, do you really care? I mean you're going to beat the snot out of it anyway why waste time/money fixing that?
On my dd, I got tired of getting an alarm every time the coolant was slightly low. The sensor finally went bad, so I disconnected it, and grounded out the connection in 2005. I watch the temperature gauge.
I think its a good thing to have. Coolant level and water temp at the pump housing for coolant exiting the engine are good things to know about.
If your coolant is somehow running low it means you have a problem with the system that should be fixed. I think the common cause of this and the easiest fix is a new radiator cap, you will get coolant pressurizing out into the overflow but not getting pulled back in via vacuum from the engine cooling down when it sits.
On the factory setup, there is a coolant level unit that the sensor plugs into, and that must be what is wired to the light on the dash. Its under the dash on driers side by the door. Can see the details in the factory wiring diagram.
Last edited by tommyeflight89; Jun 19, 2021 at 08:26 AM.
The coolant level switch seems to need some sensitive circuitry to get it to work as originally planned. I guess if you have the correct relay you can get it to work. I was not able to do it without that.
In lieu of the coolant level, I installed a coolant pressure switch on the top of the radiator in my race car. I think the set point is about 2psi. The light is on for a minute or two when first starting the car. As it heats up the pressure builds and the light goes off. Shortly after I installed it, it was fading on and off while racing. We checked everything at a pit stop and couldn't find a problem, so just kept a close eye on the water temp and looked for steam coming from under the hood. Went OK the rest of the weekend. When I got home I borrowed a coolant pressure testing tool. It turned out there was a small leak at the upper radiator hose connection, that let the pressure bleed off, but was not losing water at a rapid rate. Fixed the leak and the warning light has not come on again under normal operating conditions.
So in my opinion, the coolant pressure switch was (and still is ) a success. A lot simpler to retrofit than the coolant level.
Carl is right about a factory coolant level sensor probably being finicky to get to work and be reliable in a race car.
The best tools for saving the engine in endurance racing are a good water temp gauge to monitor temp creep over time, and a water pressure warning light to alert you right away to a catastrophic problem like a blown hose. His story about the water pressure sensor alerting him to a small leak is a bonus, and an even better argument for the pressure sensor.
Another big tip, I installed a dry break fitting on my car so I can fill the cooling system while it is hot. I use a 2 gallon garden sprayer, fill it with water and pump it up, once you connect the dry break fitting it refills the entire cooling system until water starts pouring out the overflow tube.
