Greetings ,
I finally located and installed a replacement fuel injectorwiring harness. Sorted out the fuel transferissues, installed new fuel tank floatsand …….. the engine roared life. All seemed well until after a few minutes Inoticed the temperature gauge did notmove off the low peg. ( not a usualoccurrence for a 79 XJ6 standing stillfor 10 minutes ) A little investigationrevealed that the inline resistor had gone missing. The green wire to the sensor was connected to the terminal directly. I checked the gauge and connection bygrounding the gauge wire, the needle traveled to the high end peg as per the testposted on the forum. I next hooked my multi-meter to thesensor and with the range set to 200k got a reading of 32. The meterwould not read any resistance below 200K range. ie 20K 2K etc. A second meter gave the exact same results.

My questions: Does the in line resistor need to be inplace to allow the gauge to report the temperature or is it inline to calibrate the temperature gauge. What else can I do to check the temperature transmitter? ( Not expensive should I just replaceit?) Do I need to also order areplacement resistor? ( It was installedprior to my wire restoration efforts)
Regards.
Kenn

 

Kenn:

I suspect that you do. I think the resistor was there to align resistance values between sensor and guage. A means of calibration, if you will.

Too bad, you don't have a value for it so as to get a similar one from Radio Shack or the like.

Might have a good look around the car and the shop and see if you can't spot that lost rascal!!

At times, I've found the missing parts, even when they are tiny!!

Carl

 

I'm assuming you have a Ser II, yes? Some early ser IIIs were consider "1979", that's why I ask.

On the * Ser III * cars that resistor was apparently used on an as-needed basis only when a temp gauge was reading a bit too high. That, at least, is the common theory as there seems to have been no consistant pattern as to which cars had one and which didn't.

Anyhow, adding the resistor will not make a low-reading gauge read higher.

I'm not sure if all or only some of the Ser II cars got the resistor

In your case I'd replace the temp sending unit

Cheers
DD

 

Thanks Guys
You are exactly right, my jag is and early 79 Series III. I will order the sensor and resistor from Terry's and post an update.
Sincere regards,
Kenn

 

The TempSensor was bad. Terrys OEM part was easily installed and the resistor calibrated the gauge from 80C to about 95 C its mid point. I took the car out this weekend to check it out, (20 miles) and it ran great. A few more details before it becomes an everyday driver. Next, I need to read up on testing the auxiliary fans.
Kenn