You wouldn't want the overheat light switch to fail though. Not everyone watches their temperature gauge needle. Image Unavailable, Please Login
Is there a typical failure mode for these temp senders? Is there anything like showing max reading in the same way as a failed oil pressure sensor?
The most common fault is people putting plumbers tape on the sensor mounting threads The sensor relies on the body of the switch being part of the earth (masse). Poor earths and broken wires produce high resistance = low temperatures on the gauge. A false warning light is usually a sign that a wire has broken and is shorting to earth.
It's Jaeger and not Bosch. Might be better? French vs German quality... My concerns is the plastic connector housing more than anything else. That shows the most wear.
In practice, no. The water may have too much resistance. Also, I read, water's conductivity also varies with the amount of impurities in it/how many ions it has.
Makes sense. Unless an NOS part pops up on ebay in the next week I will be resuing the factory sensor.
Thanks for the note. Not exactly sure what that means. 948822 is the new part number? If yes does it have two leads and m16x1.5 threads? I also cannot find that available anywhere.
948822 is the new part number. It does not give specifics, but as it is a change up by the factory it will be a direct replacement and have what you need
I wonder if it's a match for the Fiat sensor I bought from a parts dealer in France.... Euro 22.67 (plus P&H)
Here's the website: https://zar932.box.boutique/ I used the Fiat number 7760958 and even though the circuit diagram in post #5 showed a single pin for this type, the other diagrams we found showed two pins. The photo on the site also showed a shorter sensing element like the Ferrari one. Image Unavailable, Please Login The website is only in French, so it took a while to figure out how to order it. Even it it has two pins, that's still no guarantee that the temperature ranges are the same. It has 122* stamped on the side, which, if it represents the overheat switch value, doesn't quite match the 117+/-3C in the circuit diagram. In other words, I could end up with something completely unsuitable.
Fabulous!. The circuit diagram is for a Chinese copy of the Citreon/Fiat part. Good enough for me. ...Out of stock. There are none in the whole world!!!!
Are you saying the Ferrari 948822 is out of stock? https://www.eurospares.co.uk/Parts/948822/Ferrari/New Or just the Fiat part..... which may or may not have a two pin plug, have a 16mm thread and the right temperature ranges? I don't see me pulling the old part off my car anytime soon to compare it ... it's not easy to get to. Image Unavailable, Please Login So is yours actually broken? I have seen loose nuts on the back of the indicator causing issues. Image Unavailable, Please Login
All the Ferrari parts houses are NLA even if they say they have it. What they have is the M14 single tab version, if anything. Then I tired finding one from another OEM application. Citroen, Fiat, couple of others. None of those are in stock (discussed in the stream above). According to a FerrariofAlberta (above) 948822 is not available. My part still works so I will be reusing it. It's under the plenum so best practice is to replace everything while you have the opportunity.
Well, I didn't want to deprive you of the last remaining sensor on the planet, especially if you had a temperature issue. I just wanted to see if the Fiat sensor really is a replacement for the Ferrari item. The OEM item has a distinctive coloured collar on it, so it may be a custom sensor. I'll first establish if the Fiat sensor matches the Chinese specs, then find myself a cheap used OEM sensor to see if that matches. Then I'll talk to fellow FChatter 24000rpm in China to see if he can put me in touch with someone who can reproduce the sensor at numbers significantly less than 500. I've been told that if sufficient quantities are ordered, the sensors will cost a couple of dollars apiece, not $200 or more. However, I have the feeling that by the time I've done that, Ferrari will have already decided to remanufacture them
I was thinking that myself. Don't worry, Ferrari will way overprice the $25 cost sensor. You can get 20 for $240 from these guys on Alibaba. The problem is if it fails on a 456 you gotta pull the plenum... https://www.alibaba.com/product-detail/sender-unit-coolant-temperature-sensor-switch_60406308430.html.
I wonder if I could relocate that to the side drain plug? Would be much easier to get to. I am likely to be scolded for such non-linear thinking... #31. There is one on both sides. Image Unavailable, Please Login
I don't know how uniform the temperatures are at various points on the engine. The sensor would normally be measuring engine coolant exit temperatures. Have you checked the location on your engine to see how easy the drain plugs are to get to? You'd still have to prove that those sensors on the Alibaba site were the correct type. We are still assuming that the Fiat/Citroen/Peugeot part number is the equivalent. You could end up with the wrong part you received. On the F355 (same sensor), I can tap into the sensor wiring relatively easy to either measure the resistance of the sensor without pulling the plenum or perhaps even simulate a temperature by putting resistors across the wiring. Unfortunately, not with engine running. I would have to warm up the car, then take measurements as the car cooled. I'll try to buy some resistors on Monday (the equivalent of the Chinese specs) and see what my gauge reads.
I will try the same thing since my sensor is out. So apply 12v to wire and put in water on stove and take voltage measurements at those temps? See what temp triggers the switch right?
No power required (other than the battery in your ohmmeter). The sensor is just acting as a resistor and a switch (depending on which pin your meter is on). You have to figure out which pin is which. Not sure about the 456, but the 546M and the F355 uses a grey wire for the temp gauge and a grey/white wire for the warning light. The metal case of the sender is the earth in both cases. Best guess... Image Unavailable, Please Login The switch output should go from infinity to short circuit when the temperature reaches the overheat point. Image Unavailable, Please Login The gauge output should be a varying resistance as the temperature rises (High temp = low resistance) Image Unavailable, Please Login Hopefully the values for both of these matches the Chinese values. Much appreciated!
