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Factory 240 coolant temp gauge reliability?

joedirt

New member
Joined
Aug 6, 2017
Location
Beacon Falls, CT
Been working on getting my motor running decently and just had it running long enough to see it somewhat warm up. The temp gauge on the dash was in the red zone in no time. Granted this is a 5.0 swap car but it was previously using the factory gauges as far as I could tell. I plan on changing out the temp sensor on the intake that sends a signal to the dash gauge. But before I start chasing overheating issues how reliable is the factory temp gauges on a 240?
 
240's have a known temp gauge problem. But your issue may be a mismatched sensor.

Very true I never had the car running long enough to know if it ever worked correctly. I cant imagine simply wiring up a ford sensor to a Volvo gauge would just work lol but it was put in with a Converse kit so idk.

I planned on replacing the entire old gauge clusters with autometers anyways. Guess ill start with a coolant temp one first.
 
My '00 Explorer 302 with Ford OEM temp sensor and 90 degree thermostat placed the '82 Volvo gauge dead center.

You didn't identify the MY of your 302 and I didn't take the time to look at your build thread. My 302 from '96 through '01 and probably beyond used two temp sensors, one for the dash gauge and the other for the PCM. My PCM sensor failed and it took some time to figure out that the dash gauge could read properly while the PCM thought the engine was stone cold.
 
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As we discussed Ian, use a bushing to mount the correct Volvo sending unit for your car/gauge in the intake manifold cooling passage on the driver's side front near the t'stat. Gauge should read pretty close to center with the OEM 192/195 Ford t'stat. If you want to alter where the gauge reads, experiment with different small resistors in the wire from the sender to gauge.
 
My '00 Explorer 302 with OEM temp sensor and 90 degree thermostat placed the '82 Volvo gauge dead center.

You didn't identify the MY of your 302 and I didn't take the time to look at your build thread. My 302 from '96 through '01 and probably beyond used two temp sensors, one for the dash gauge and the other for the PCM. My PCM sensor failed and it took some time to figure out that the dash gauge could read properly while the PCM thought the engine was stone cold.

I don't know the exact year but it is from a fox body (possibly 89 but I don't know exactly, it is a mass air HO motor). Yes it does have the two different sensors one near the thermostat housing for the gauge and the other more towards the firewall for the PCM. Was gonna change out the gauge sensor to be sure and test it outside of the car and compare it what the gauge reads.
 
As we discussed Ian, use a bushing to mount the correct Volvo sending unit for your car/gauge in the intake manifold cooling passage on the driver's side front near the t'stat. Gauge should read pretty close to center with the OEM 192/195 Ford t'stat. If you want to alter where the gauge reads, experiment with different small resistors in the wire from the sender to gauge.

Yep gonna order a new sensor today and double check my intake manifold to see if it has that bushing already installed which would at least give me a clue as to if it in fact has the Volvo sender in it.

You suggested testing it outside of the engine with a thermometer to get a idea of the what the gauge is reading, so if I were to say in theory I extend the single wire going to the sensor so it could reach a BBQ grill next to the car while I boil pot of water. Would extending the wire throw anything off enough to make it not accurate compared to being connected at the motor with the stock length wire?
 
WOn't help. The gauge grounds through the sensor. If you used some wacky electricity proof thread sealer or something, the sensor just wouldn't ground, and the gauge would read full cold. There's no way that poor grounding of the sensor body would cause the gauge to read high.
 
WOn't help. The gauge grounds through the sensor. If you used some wacky electricity proof thread sealer or something, the sensor just wouldn't ground, and the gauge would read full cold. There's no way that poor grounding of the sensor body would cause the gauge to read high.

Even just for testing the sensor outside of the car grounding the sensor out with alligator clips or whatever?

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Sorry, I wasn't reading completely enough. That would work for what you're trying to do.

When that faker board goes it can do anything. ALl you need to do is pull the tiny circuit board off the main board and jumper a wire between 2 of the 4 contacts.
 
I don't have a chart for the specific temp sensor for the Volvo but had the same problem on my Jag-u-are. Gauge and OBDII data port was reporting temperatures 10*C higher than an IR temperature gauge was reading on the head and significantly higher than the 84*C thermostat verified good on the stove test.

The problem was that the correct temp sensor was reading 30 ohms too low. It took the third new sensor before I found one that provided a resistance level that was closer to what the IR gauge reported in degrees. If you poke around on the net long enough you might find the actual degrees/resistance chart for the correct sensor.

Now the logic link; the Jaguar used the same sensor as the Ford 5.0L in my 245 Volvo and the Ford sensor moves the Volvo temp gauge to about one pointer width below the mid range expectation with an 80C thermostat.

Here is a link to the actual resistance chart created from my stove top/DVOM measurements. Your mileage may vary.

30 ohms change is 10 degrees C in the engine running in normal temperature area of the sensor varisiter

http://www.jaguarforums.com/forum/xk...2/#post1194994
 
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And to Testpoint's point -- when I was playing with this when the 5.0L was in the car I had a 180F t'stat in the motor. When I put a 10 ohm resistor in the circuit, it bumped the Volvo gauge up from the lower 1/3 to the middle when I was cruising down the road with enough flow to keep the fans off.
 
That's what I was pointing at Tom - with the difference in operating temp, moving the needle a bit towards the red gave me a little more 'comfort' margin. LOL - eventually I guess a gauge that actually reads out a temperature might be a step forward....
 
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