Coolant electrical resistance

[JohnA]

In the process of troubleshooting electrical gremlins (most likely due to the UKSpec sham of an alarm) I connected the positive of the digital multimeter to the battery and the negative on to:

 

1. radiator top (plastic) 0V

2. coolant inside 11V

3. coolant expansion tank (plastic) 0V

4. coolant inside the tank 3-3.5V

5. metal parts of the engine 12.4V, same as the battery at the time.

 

These coolant values do look a bit too high to me:blink: . The coolant is just over a year old, so no deposits and such. It shouldn't be so conductive FFS.

Has anyone got similar values from their car? I know it's not done usually, but it's dead easy to check.

[Chris Wilson]

You bored or something John? Let's all run a Geiger counter over the engine too, and post up the results

 

Coolant with A/F in it IS quite conductive, a lot of low coolant level sensors work that way.

[JohnA]

No Chris, but recently I'm getting a dry 'click' first time when I try to start the engine, and I'm scared that something is draining the battery (which got totally empty last time it was left unused for 2 weeks)

 

Chris, if those readings are OK then fair enough.

That voltage is much lower on other cars though.

[Chris Wilson]

How much current draw at rest is the battery seeing? I soometimes get cars with lots of "gizmos" in that are pulling silly current from the battery even when everything is supposedly off. Alarms sometimes seem to be a common denominator, but the alarm experts seem to decry that theory. All I can say is most of these problems start when a factory stock car has "things" nailed onto the electrical system

[Marty]

If its water based it will be conductive?

It'd be more than likely a alarm draining your battery to that extent i wouldve thought, mine will do the same thing if i leave my car standing too long. Either that, or maybe your battery is on its way out ?

Not much help am i

[JohnA]

How much current draw at rest is the battery seeing?

Can't remember now, I had checked it months ago and it was 'too much', a good fraction of an Amp I think.

 

I had measured it by disconnecting the battery and fitting the DMM in series in 'Current mode'

The alarm had a fit, and the ECU reset along with the trip meter etc, so I try to avoid disconnecting the battery if I can.

 

The altenator provides proper voltage and the battery is less than 2 years old.

...most of these problems start when a factory stock car has "things" nailed onto the electrical system

Probably not the case here, I am king of stock in case you've missed it.

I go to great lengths before changing something away from stock - it needs to make a good case, and the vast majority of aftermarket offerings are overpriced substandard tat in my lonely view.

[Kev.O]

No Chris, but recently I'm getting a dry 'click' first time when I try to start the engine, and I'm scared that something is draining the battery (which got totally empty last time it was left unused for 2 weeks)

 

Chris, if those readings are OK then fair enough.

That voltage is much lower on other cars though.

 

If I leave my car for two weeks the battery is flat and I don't have any after market goodies

[JohnA]

I see yours is UKSpec as well.

 

We're not the only ones you know, there must be a fault, something that ages badly and leads to excessive current draw, even when the alarm is not used. You can't leave this car for a week or two and expect to start it again. It sucks.

[fredm]

I have heard that you can use "conductivity" measured with a dmm to give you an idea as to how well your antifreeze is performing, I'm not sure what readings would be classed as good or bad though. I have a feeling it's not too accurate though. I suspect you will agree that the prefered method is a Refractometer.

 

But anyway, I thought I'd post up my results for your interest.

 

Positive dmm probe onto battery +

 

Negative dmm probe into Rad coolant 12.35v

########### into Expansion Tank 9.5v

###########onto cylinder head 12.35

 

Interestingly if you connect Negative dmm probe to battery -ve and then probe rad coolant with +ve probe I got 0.3v

 

Cold engine,not used for a week. Coolant, Toyota oem 3 months old.

 

As for the parasitic drain on the battery, with a dmm set to dc amps placed in series with the -ve battery terminal and -ve lead I have 0.03amps drain. My car is standard with no gizmo's fitted, the oem alarm/immobiliser has been binned, no remote locking for me. I have left my car for 3 weeks and it starts like it was last used the day before.

My previous 94 UK could also be left for a fortnight with no problems, that too had the standard immobiliser/alarm disconnected.

 

As you say you must have a drain somewhere. Happy hunting!

[JohnA]

I have heard that you can use "conductivity" measured with a dmm to give you an idea as to how well your antifreeze is performing, ...

 

Thanks for the feedback mate.

You are right, connecting (-) to the block and (+) in the coolant you get an idea of the conductivity of the coolant. The more tired it is, the more conductive it gets - supporting the creation of electrolytic deposits all over the coolant channels.

 

Below 0.3V is good, 0.5V or over means that the coolant needs urgent flushing.

 

That's what I should have measured in the first place, but I had a few glasses of wine and couldn't think straight:blink:

Because there was no interest in the thread I didn't bother coming back to rectify it.

 

I'm almost certain it's the UK Alarm responsible for the drain, it's been doing it since I got the car, now it may have got worse though.