gauge accuracy, electrical expert help needed

[vick79]

Hi guys, I'm working on getting gauges to work. Here's what I've done so far.

1) found bad voltage limiter, removed and replaced with 7805 limiter.
2) cleaned all the grounds and contacts on bulkhead, cluster etc
3) checked temp switch (sensor) reads correct resistance (10-73). Replaced anyway.
4) Built a C3826 tester with 11/22/73 ohm settings.
5) checked gauges tabletop with new 7805 limiter and my tester, gauges work fine. 22ohm setting reads slightly left of middle. 11ohm setting reads almost to 250. Tested oil, fuel gauges also, So I know the all work fine.
6) reinstalled back in car, checked gauges with C3826 tester, they read fine.
7) voltage at temp plug reads solid 5V

But!

Plugged it back into temp sensor, at operating temp it read 27ohms, but gauge barely reads halfway  between 120 and 170.

Its working but with very poor accuracy. my tester was built with 1/4watt resistors do you think thats why gauge works better with that than real world sensor? Not enpugh current to drive the gauges?The 7805 puts out about 1amp, is that low for this circuit?

I ordered an RTE limiter, but im trying to narrow down this issue.

[b5blue]

Dig through this it may help: http://www.dodgecharger.com/forum/index.php/topic,37999.0.html

[vick79]

Pretty much did exactly that table top, my tester box is identical. It behaves normal when plugged into the tester, but when plugged into the engine coolant sensor its extremely inaccurate low reading on the gauges.

[vick79]

I feel a bit foolish, turns out my poor gauge responce is more likely a thermostat that's stuck open!

[resq302]

yup, that'll do it!

[vick79]

Well i found out my 440 came with a 160deg thermostat from the prior owner. So the temp reading between 120-170 was actually normal! Swapping in either a 180 or 195deg thermostat right now. 160 runs too cold and rich.

[b5blue]

There ya go.