Weird behaviour of electric water temp gauge.

[Agustin Alfonso Cesar Charles]

So, not too long ago, I installed an electric water temp gauge. It works nice, but something is bugging me, when I turn my flash lights, the needle bounces as the light flashes, if I turn the A/C, it reads lower than it should, if I turn my headlights the same thing happens.

I know I have an old car, but I haven´t really started digging to see what´s going on, I did measure my voltage and it was 14.5 with no accesories, and with everything on, it went to 13.5, and stayed there, all this at idle. The battery is brand new so, I ruled that out.

What I thought is that maybe I may have a ground problem, because, the sender ground is bolted to where my fuse box ground goes, and the indicator ground is bolted to my dash, should I ground both thing to the engine instead?

Tomorrow I will do a parasitic test just to check my electrical system to be sure that everything is fine.

Topic

[Erin]

How much bounce (during flasher op) and drop (during AC op) are we talking? Like a tiny bit or does the needle peg on the low end?
I am gonna assume we are talking a tiny bit.

A lot of cars tend to do stuff like that. Maybe not brand new ones (sometimes even then).

There *might* be some kind of tiny electrical problem but if your voltage is still at 13.5 with everything on and 14.5 without AND the bounce is not drastic, you probably don’t have anything to worry about.

Maybe you could wire the gauge to some other branch?

One other thing – whenever something electrical turns on in a car, house, etc… there is a split-second power surge and the newly powered branch tends to hog power from the rest of stuff for that moment. Kind of like in your house when the A/C turns on and the lights dim a little bit for a sec.

[asetoftools]

The way I fixed my turn signal making my voltage drop was installing a 1 farad cap to smooth out the power fluctuations. Maybe its a sensitive gauge. I only ever had battery voltage drop not any temp gauge.

It made it better, but it did not completely solve the issue. I think sometimes old wiring gets a higher and higher resistance in it, which is why things like turn signals draw more than they should. The manufacturers always install the highest gauge they can get away with i think. I have upgraded some cars with 4 gauge positive from battery to alternator and negative battery to engine block, negative alternator to frame, which has also helped with issues like this. They call that the ‘big 3’ upgrade in car audio circles:
http://blog.vminnovations.com/how-to-the-big-three-upgrade/

But dont forget to fuse it off with something like 100 amps (for 4 gauge).

[Agustin Alfonso Cesar Charles]

Thanks guys, well, the needle goes like 10 degrees colder when it fluctuates, and with the A/C I noticed that the thing is with the blower fan, because if I disconnect the compressor the needle doesn´t change, but changing the blower fan speeds the needle goes from 2 degrees difference (lowest speed) to almost 10 degrees (maximun speed).

The good thing is that it doesn´t fall more if the light flashes, so I believe there must be a maximun current drop. But since the car does have an old wiring and the only upgrade it has is moving the battery to the trunk for security reasons :P, I will do an upgrade for the alternator wire, because I did upgrade the battery cables but nothing else besides that.

I will do that “Big 3” thing, since I know I have a good ground (I actualy used dual cables for the ground of the engine and the battery, so I need to go up for the positive side.

[Author]

Replies