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Temp Gauge

Posted: January 23, 2018, 10:50 am
by troymn
Hi. I replaced my consistent voltage regulator with a Scott Drake one Just because my fuel gauge was a little off. Fuel seems good but now my temp gauge reads high. I have tried a different temp/ speedo cluster I had laying around. Same problem. The truck has a new thermostat (180*), aluminium radiator with electric fans that come on at 185*. Tried a new temp sensor. I can see the gauge drop when the thermostat opens and when the fans come on but the gauge is reading 220*ish when that happens.I checked the voltage to the gauge and it was something like 5.4ish volts. I have seen people reference adjusting the voltage resistance. How can you adjust it? Thanks!

Re: Temp Gauge

Posted: January 23, 2018, 2:28 pm
by troymn
Am I just overthinking this? Do they mean coil up some thinner gauge wire and adjust the length till it's in spec.?

Re: Temp Gauge

Posted: January 23, 2018, 4:44 pm
by Toyz
First course would be to verify actual running temperature. If incorrect, then replace the sender. I am not sure why the replacement would read high, while correcting the presumed fuel inaccuracy. Normally, "tweaking" of fuel indication is done via sender arm adjustment.Adding a small resistance to the temp sender wiring would correct your situation, but would be a "hit or miss". When working with early fuel injection systems , I used to empty out Radio shack's supply of resistors to achieve my wanted signal!
In your case, I suspect a new temp sender specific for your truck will do it. You can make a trial measurement on the old removed IPR, with it under load, to see if there is a discrepancy in voltage output there. 5.4 is within range in my experience, however. Service manual test procedure shows 0 to 10v oscillating; 3v should represent a maximum reading at the gauge.

Paul

Re: Temp Gauge

Posted: January 23, 2018, 6:05 pm
by troymn
Yeah I have an aftermarket temp gauge and a Mr. Gasket termocap on order. I was going to try and make sure the temp is good before messing with the stock gauge. Everything is new so I can't for see anything wrong. Just frustrating buying new parts that don't work as they should. I have adjusted fuel level buy bending the arms also but, Thought I would give this a shot.

Re: Temp Gauge

Posted: January 23, 2018, 10:13 pm
by unibody madness
Just to help clarify in my mind. I had a 160 thermostat in my 460 that read just below 160 at normal operating temp. Last year I got stuck in traffic in 116 degree temps and overheated... it ran upward of 200 on the gauge. long story short I ended up replacing the fat back radiator that had cost me an obscene amount of money to re-core in copper for a three row aluminum radiator with twin fans. It ran half way between 115 and 160 on the gauge so I replaced the 160* with a 180* thermostat... it still runs just below 160. How do I test the gauge to make sure it is reading correctly?

Re: Temp Gauge

Posted: January 28, 2018, 10:09 am
by deadheadno1
One of the best tools my Sweetheart bought for me when she wasn't paying attention to what was in the shopping cart was an infrared temp gun. Well spent twenty bucks!!!
Tom

Re: Temp Gauge

Posted: January 29, 2018, 1:54 pm
by troymn
forgot to up date this. Yeah I have one. Used it, an aftermarket mechanical temp gauge and a Mr. Gasket thermo radiator cap. Every one said the system is working properly. So that means the factory gauge is off. Is there any adjustment other than buying resistors from an electric supply store?

Re: Temp Gauge

Posted: January 29, 2018, 7:56 pm
by 9Fingers
I once built a lawnmower with a twin cylinder Briggs engine. Had an old Sun tachometer salvaged from the trash dump. I wired the output from one side of the alternator from the engine through a second diode to get a DC current, same as the other side that was charging the battery. Then I wired a potentiometer in series between the diode and the tachometer. Crank engine, use mechanical tach to see real RPM, adjust the potentiometer (variable resistor) with a screw driver to dial in the tach to read correctly.

Without being able to see a temp gauge, if you move forward with the resistor, I would disconnect the gauge and measure the resistance through the gauge. Then get a potentiometer that is adjustable from 0 ohms up to the same resistance as your gauge. Take the wire from temp sensor and attach it to the center, adjustable leg of the potentiometer and take a wire one of the other legs on the potentiometer on to your gauge.

Crank truck, let it heat up to operating temperature, check temp with your other tools, slowly adjust the potentiometer to get the reading you need.

This should drop an appropriate amount of voltage across the potentiometer and dial your gauge in.

Re: Temp Gauge

Posted: January 29, 2018, 11:06 pm
by troymn
Thanks 9Fingers!

Re: Temp Gauge

Posted: January 29, 2018, 11:10 pm
by troymn
Thanks 9Fingers!

Re: Temp Gauge

Posted: January 31, 2018, 10:00 pm
by Toyz
The stated method will likely give you an accurate measurement at normal operating temperature, but will likely skew the readings at higher and lower ranges. After verifying a good ground at the sensor (no insulating tape, etc), why not just buy a quality replacement sensor?
Paul

Re: Temp Gauge

Posted: February 1, 2018, 11:11 am
by troymn
First thing I did after replacing the consistent voltage reg was replace the sensor. Didn't work. Over it. Put the old cvr back in. I will just buy a quad gauge eventually and switch it over to 12 volt. The kits I am looking at are spendy do to the fact you replace the float, oil pressure, and temp sensors to ones made for the gauge. Might be later in the year. Thanks for the input everyone.