69 S2 4.2. It is 80 degrees out - highway speed, the temperature needle sits at the way upper edge of ‘normal’, just touching the red. Car doesn’t feel like it is hot. Is this normal?
First step, I bought a new solid state voltage regulator, and figured I’d ask before ripping stuff apart: where does this go? Inside the central dash panel that pivots out? Or do I need to pull off the underside panels for one of the sides of the dash?
Third question: the radiator fans ran immediately when I switch on the ignition. I troubleshot it - the relay is fine, it is the otter switch. But when I reverse the wires on the otter switch, the fans do not run when I start up. I have yet to verify that they run when it is hot. Question: is one side of the otter switch grounded to the chassis, so that was the problem? Or is the otter switch defective? Why are there two wires going to the otter switch, if one side is grounded? I will never show this car, so I assume the best solution is CoolCat’s one wire sensor.
Temp gauge. Before you touch anything, you need to KNOW that the temperature is normal. The best way to test is to use a stick on thermometer at the thermostat housing, you can buy one from my store. If you are actually running hot, we go in one direction, if you aren’t, we go in another. I posted a lengthy study of available temperature sensors here last year, they’re mostly crap. It’s sometimes better to mentally compensate for a bad reading than to drive yourself nuts trying to find a sensor that plays well with your gauge.
The IVR is mounted to the back of the fold-down gauge panel. But if you were having trouble with the IVR, you would have trouble with both the temperature gauge and the fuel gauge.
Radiator fans. I think that your radiator is grounded somewhere. The radiator should be electrically isolated by rubber bushings at each point where the mounts meet the chassis. They’re often missing on the radiator side stays. One of the wires on the otter comes from the fan motors, the other is a chassis ground, which should be the only ground anywhere around the radiator (this was a blunder on the designer’s part, corrected by an isolated otter switch in the last few cars). The wire from the fan motors should go to the center, while the ground goes to the flange tab. If the radiator is grounded and the wires are reversed, the fan will run all the time. If you then reverse the wires, the fans will work normally as long as the otter is functional.
Mike F’s words should be taken as gospel. You MUST be sure that the true operating temperature is OK. Then, assuming that the gauge still reads too high (and you don’t want to just live with it), you can bring the reading down by soldering a small resistor in series with the gauge.
My gauge has no numbers — it just says NORMAL. Since I have warmish thermostat (180 or 190 F), I wanted it to read a little above center on the gauge – it was reading somewhat hotter. I actually ended up with 2 or 3 resistors in parallel with each other, the whole being in series with the gauge. The total resistance added is on the order of 15 to 20 ohms. Now the gauge reads right at the “L” of NORMAL.
Thanks for the input. I have confirmed the radiator fans are blowing the correct direction, also that the otter switch does switch on when it gets hot.
Next step, even though I don’t know it is bad, is that I distrust old electric technology, so I will put on the solid state voltage regulator.
After that, I will try to measure temps. I have an IR reader, and the trick here is to put a piece of black electrical tape on the surface you want to read. Reading off a metal surface is wildly variable, because it is highly reflective to IR and the emissivity is unknown, but black plastic tape works. I will also get some stick-on thermometers from CoolCat. In the olden days, my Triumph Spitfire always read hot. I ended up running it with no thermostat, because I was 17 years old. These days I realize that the instrumentation might be the issue.
As everyone has said so far, make sure the car is actually running hot before you try fixing something that ain’t broken . I ve been using IR guns for years on a variety on things from cars to marine generators and air con coils and they incredibly useful. I always have one in the car. Yes some surfaces can affect readings but most won’t really make a difference.
If the engine is really running hot while driving over 40/50 mph it s not a fan issue.
Have the same year car and had similar issues. Besides doing what MFrank wrote above, I also checked into a replacement temp sending unit. The sending units are not expensive and just one less variable. This car ALWAYS (owned for 35 yrs) ran in the N N-O range on NORMAL. I had the original radiator recored in about 1991-92. A few years ago when this started, I ended up buying a CoolCat radiator and upgraded fans. Issue resolved. Here is a photo of the new IVR in place.
Thank you WoodBoatChick. I was looking for a voltage regulator that looked like the replacement, so was staring right at it. Is that an S2? How did you get the dash panel to fold all the way out? I need to remove the pivot bolts, as the switches hit the radio bezel.
In the meantime, I verified the Otter switch does switch on when it gets hot, and the fans are turning in the right direction. On a recent rebuild, I think the radiator was sent out for repair and resealed, so it ought to be in good shape - I will ask specifics from the rebuild shop as to what was done.
Here’s another way to test the sensor readings. Remove the sensor and suspend in a small electric kettle, make an extension to the sensor terminal wire and attach a ground to the sensor body. Place meat thermometer in water (smuggled from kitchen drawer!) and heat up water slowly comparing the gauge reading to the meat thermometer. Worked great, reading were pretty close and spot on at 100C.
