I have a '72 Cutlass with a 350 4BBL in it. I just switched out the idiot lights for gauges and put in the sending units that were sent with the kit from the Parts Place.

On the Temp gauge it's up in the HOT range, but I never got a hot light with the idiot lights.

Suggestions on what to do or check?

 

What gauge is it? What is the temp reading on the gauge? I think the idiot light sensor-switch turns the light on around 260 (on most aftermarket stock replacements) if I recall correctly.

Maybe there is an air pocket around your sensor. Are there any visible signs the engine is really that hot?

 

One easy check (this assumes you have a fairly good thermostat) is to start the car cold and feel the upper hose or the rad inlet. When you start feeling heat, check the reading on the gage. Should be close to the t-stats rating. Won't answer all your questions but it's something.

 

Use an IR thermometer to check actual temp. next to the temp sender.
Yes, easy to have an air pocket in there.
What T-stat are you using?
What gauges?

 

It's the Rally gauge package with the fuel, temp and oil.

 

I'm pretty much a novice when it comes to the mechanical end of an engine. When you say there may be an air pocket around the sensor, how do you get rid of that?

 

Gotta bleed it out.

Start car with rad cap off and you'll see the coolant dropping, keep adding coolant until full. Doesn't hurt to have the front of the car up a little bit.

The IR Thremo is a good thing to have. My temp gauge is off by 40* Reads 220 and it's really at 180*. I took readings with this thing EVERYWHERE. The upper hose will be a high temp than the lower

 

It's the Rally pack gauge from the Parts Place.

I replaced the thermostat, just in case. It had a 195F in it and I replaced it with the same. No change in the gauge. As the engine heats up the needle goes right past the "H" and pegs at the top. There isn't any indication that the engine is overheating and when I had the idiot lights in the dash, the HOT never came on.

I checked the wiring to the gauge and it is as it is supposed to be.

It almost has to be a faulty temperature switch/sending unit doesn't it?

Any other ideas before I change out the temperature switch/sending unit?

 

Is there a thermometer type temperature guage that can be inserted where the sending unit goes, or better, where the TVS goes. This would confirm the actual coolant temperature.
I seem to recall seeing actual mercury thermometers that used to be used in older cars.
If the gauge needs calibrating then Rob has posted some good data for that.
Good luck trying to get help from the parts place.

 

Infrared thermometer. Instant contactless temp measurement!

 

Rob,

Going to buy an Infrared thermometer tomorrow. Can you recommend a brand? I doubt I'll use this much. Wouldn't you think that this cluster package should work correctly after installaton withou having to go through all of this?

I read what you did to correct the problem in your car, but it's way over my head what with the OHMS, ect. Not sure what I'm going to do.

 

When I first put my fuel-injected engine together, I was using a set of electronic gauges and it was always showing high temp readings - 220-240 degrees. I tried the whole gammet of fixes - clutch fan, fixed fan, thermostat, four row radiator, timing, electric fans, whatever I could think of or get recommended by others. As a last resort, I changed to a mechanical guage and guess what - 195-205 degree range. Sometimes you have to learn the hard way!

 

Rob - how accurate really are the IR units? You have written in other posts about the best way to use them.
Has anyone ever aimed one at the top of a pot of boiling water (with the pot moved to a non heated surface), and adjusted for sea level
http://www.engineeringtoolbox.com/bo...de-d_1344.html.
Rick - Radio shack sells the resistors for peanuts, and they really are easy to add to your gauge lead if you need to. If you are not worried about appearances they can be inserted anywhere so you do not have to put them way up under the dash. Start with a small one and work your way up until the gauge reads midway at your thermostat temp.

 

I have used name brand units and cheapos from Harbor freight - both within a couple degrees. I found it works great on engines. When i installed my gauges, I found an overheating condition on my car that I repaired (wrong radiator and bad clutch). After that I had an air pocket int he motor and once that was out, the needle rides about in the middle at 175* and HOT is 214*. I did the calibration but never did install resistors, as I now know what line indicates what.

 

Bought an IR thermometer. Checked the temp right by the temp sending unit. After taking the temp several times, it averaged 195 degrees.

The gauge still read as far past the "H" as it could go. I changed out the temp sending unit that the Parts Place sent with the kit for an AC/Delco unit. The gauge read at the mark between the middle and the "H". Next, I changed the 195 stat to a 180 and the gauge now reads right in the middle as it should.

In defense of the Parts Place, I've bought a quite a number of items from them and have not had any trouble until the temp sending unit.

 

Glad you solved it. Lots of people had issues with the PP sending units. With as much as they marked them up, they shoulda worked just right!
Your IR thermometer will come in handy for many things. Meat temps, checking your A/C performance, checking in your ears for fevers, etc, etc!