2H temperature reads zero (2 Viewers)

[cruiserdenmark]

Hi!

My temperature reads zero all the time. So today I checked the connection to the sensor. Following Haynes manual I connected a ground to the sensor wire and turned the key to "ACC". The gauge did rise, so that works. Then I measured the resistance in the sensor (between sensor and ground), and it was ~400 Ohm. I think that is OK with a cold-ish engine. So then I connected the wire to the sensor and turned the key again - reads zero again. It shoudl move a little up at 400 Ohm, right?
I have probably overlooked something, but I can´t find out what I am missing here. Any suggestions?

 

[Infinity00]

Check out this post, I haven’t read it in a long time but I bookmarked it because there’s a lot of good info here. In the first link, post 19 is the same as the 2nd link below.

More Thermostat/Temp Gauge nonsense


Temp Sending Unit?

 

[OSS]

400 ohms won't show anything on the gauge. 130°F (which won't register on the gauge) is 204 ohms on a 2F sender.
170°F is 90 ohms on a 2F sender.

 

[Infinity00]

New $26 sender needed, you think?

 

[cruiserdenmark]

Thanks for the tips. I made sure the connection was good yesterday and watched the temperature carefully during today. It seems now that it actually works, but it is very near zero after 30 mins driving. Any opinions on that? My motor is a 2h and I drive like an old lady.

 

[OSS]

If the thermostat and temperature reading stuff works, the engine should warm up to operating temperature within 10 minutes or so and the needle should be getting near the middle of the gauge. Old lady or not. At least that's how it's supposed to work.

 

[cruiserdenmark]

You're right. I'll start with replacing the sensor then. Could be an aftermarket sensor that doesn't do much, according to this thread:
1985 FJ60 Coolant Temperature sensor / no reading on dash!

 

[cruiserdenmark]

New plan. I just checked the resistance in the sender unit before and after 10 mins driving. Before it was 954, after it was 40. So the sender is working and the thermostat is probably also fine. Could be a bad ground in the temperature gauge then Will have a go at that later today. I also measured the current from the gauge, and it was pulsating up to 8 V. So I think it is the ground in the gauge.

 

[cruiserdenmark]

Update. I took the gauge apart, and gritted the small contact as suggested for these kind of problems. No change. So now I am going for a new sensor.

 

[Infinity00]

It took me 5 minutes to pull my sender yesterday. Very easy, just a tablespoon or two of coolant comes out if there’s no air pocket. 17 mm wrench and a step stool. I didn’t have to remove anything but the connector

 

[cruiserdenmark]

Great. I thought I had to drain the coolant first.

 

[Infinity00]

Oh, pop the radiator cap off first to release any vacuum before you pull it

 

[emac]

Check the connector. Maybe it is corroded or the wire is broken within the insulation right before the connector. I had a similar issue and I replaced the spade connector and that seemed to fix the problem. when hot jiggle the wire and see ifthe guage jumps up

 

[cruiserdenmark]

Thanks. I tried that, but did not work. Also, the gauge goes up if I ground the connector, so it should work. But I've replaced the space anyway just in case. Trying to late a temp sensor around here. Apparently not so easy...

 

[cruiserdenmark]

So I found a new temp sensor and installed it. This is how far the gauge goes after 30 min driving. Sorry for the bad picture.Do anyone have an opinion whether this is acceptable, or I should try to change thermostat as well? (and if so, will it be possible to keep the old gasket in the t-stat because I could only find one nearby without the gasket?)

 

[Tapage]

that position of the needle in Tencha = 176F average ..

 

[cruiserdenmark]

Thanks. That is too low. Going for the thermostat now then.

 

[Infinity00]

I’m curious if the old thermostat was 180 when you pull it. The one for our vehicles, as you probably know, is 190 deg.

 

[cruiserdenmark]

I will follow up. So far I ordered one from UK that got lost in the mail...
If anyone knows where to buy a decent and not too expensive one in EU, let me know.

 

[cruiserdenmark]

Only a year later: follow-up! (sorry for the delay)
I didn´t dare to put the aftermarket thermostat in, so I ordered an OEM one. A couple of months ago I switched it in. Now the needle is sitting in the middle, with some random peaks (1-2mm) upwards while driving. The old thermostat was a 180F (82c) one. The new is 190F (88c).
Thanks for the help, it is much appreciated.

By the way, took the car on a family trip to Norway right after changing the thermostat. We went to the top of a hill, got out, and it started spilling coolant like hell. Then a crazy vacuum in the large tube between radiator and engine. Luckily I had a brand new radiator cap with me. The old one had cracked gaskets and all. So I put the new in and it worked fine. Been working great ever since (daily driver).

Cheers!