No way is that circuit senstive enough to detect coolant concentration. The quality of the water supply will have more of an effect on resistivity than the antifreeze concentration. There is a huge difference btween hard tap water and de-ionized water. When the ignition is first turned on the warning should blink for a few seconds as the bulb check. The circutry for that function is part of the foil circuit board. Sometimes the timing capactior goes and the light will blink for a long time. Sometimes the coolant level control relay will go bad making the light blink forever or never turning it on.

Dennis

----- Original Message -----
From: John Rodgers <inua@CHARTER.NET>
Date: Wednesday, February 8, 2006 3:37 pm
Subject: Re: How to - or not - bleed the cooling system

> Robert Smythe wrote:
>
> > My coolant light flashes at startup, then goes out, temp guage
> never goes
> > past half. Am I fooling myself in my speculation that its just
> testing> the
> > function of the circuit with this behavior?
> >
> > Robert
> > 90 MV
> >
> >
> You are correct.
>
> The specs call for a coolant mixture of 50/50 coolant to water. That
> mixture gives a specific resistance between the two electrodes on the
> coolant level sensor. Evidently on startup the circuit assumes an open
> circuit or infinity resistance until the correct voltage for the
> circuitis read,  at which time the light goes out. If the mixture
> is incorrect,
> or the tank is low on coolant and the electrodes exposed, the
> resistanceis incorrect, the voltage reading is wrong and the light
> will come on.
> Important to keep that coolant mixture at 50/50, as well as
> keeping the
> tank full.
>
> Regards,
>
> John Rodgers
> 88 GL Driver
>