Temperature Gauge

[WeeWun]

I am new to the Forum and am impressed with the knowledge contained here in. While we have a 2014 ES350, which we are totally satisfied with, our Grandson has a 92 LS400.

Was able to fix his CEL, OBD code 71, after reading the posts in this Forum, which is the reason I joined. He has another problem, the Temperature Gauge is not working. He took it to a local shop and they said it was the Instrument Cluster and would take $1,000 to repair. The engine appears to be running at the proper temperature per my Infra Red thermometer.

Before investing in an Instrument Cluster I want to eliminate the Temperature Sender and wiring. I will appreciate the following info if any has it:

1. What is the "cold" and "hot" resistance of the Temperature Sender.

2. What voltage should I read at the end of the connecting wire to the Temperature Sender both connected and disconnected.

3. Will it be safe to connect the wire to Temperature Sender to Gnd to see if the Gauge deflects.

The above is all I can think of to do but if you have any suggestions/advice I will appreciate your input.

[LSPaul]

The shop manual has a process to see whether it's the sender or the temp gauge portion of the instrument cluster. It's in the "body electrical" section of the manual, pages BE-175 and 176.

To check the sender, the manual tells you to start by disconnecting the temp sender wire. With the key on, the temp gauge should read 'cold'. Next, ground the sender wire through a 3.4 watt 12v bulb--(a 194 is probably close enough at 3.8 or so watts). Put the bulb in series with the sender connector, connect a test lead to that and ground it. Then, turn the ignition switch on. The bulb should light up and the temp gauge should climb. If that is the case, replace the temp sender. If not, you'll need to take out the instrument cluster to check resistance on the connections to the temp gauge.

Once you've disassembled the instrument cluster, the manual says to check resistance between the three connections on the back of the gauge. Between terminals A-B, it should be approximately 173 ohms. Between A-C, 54 ohms. Between B-C, 220 ohms. If this isn't right, then I suppose one could get a used cluster from a junkyard and remove the temp gauge part to replace in your grandson's car.

There's two coolant temp sensors/senders that are adjacent to each other under the hood. They're located just behind/underneath the top side ignition coil in the intake manifold--a bit of a pain to get at. I've pulled the air intake ducting, then removed the cover over the ignition wires, then removed the top ignition coil to get at the sensors. The sender that drives the temp gauge is a one-wire sensor, not the green-colored two-wire connector, which is for the coolant temp sensor that connects to the ECU/FI system (if that one's bad you'll get trouble code/DTC 24).

Hope this helps.

Paul

[Exhaustgases]

taninautoelectronix.com I think that's the site. They can fix the cluster if you can't.

[WeeWun]

Paul and Bob, thks for the replies. Exactly the info I am looking for. Have been looking for a Service Manual for the 92 but have been unsuccessful.

[LSPaul]

I've seen paper shop manuals (one manual for the car, one manual is for the electricals) pop up for sale on the usual online auction website. Otherwise, one can go online to Lexus' site; for $15/day, you can buy access to Toyota/Lexus TIS (technical information system) and download what you need or as much as you can download in 24 hours' time. All of the sections are in Adobe Acrobat (.pdf) format.

Paul

[WeeWun]

I appreciate your input, but I need more.

I am going to go over and work on my Grandson's Temperature Gauge and would like to be prepared. I would like to have on hand the Temperature Sender (single wire) and Temperature Sensor (two wire) that are located on top of the engine.

I get confused when I browse for the Temperature Sensor as there appear to be two of them, one down by the lower Radiator Hose and one on top of the engine by the Temperature Sender, evidently they are different sizes and specs. I will appreciate the correct PNs and best Source.

Paul, appreciate the tip on the Service Manual source, am going to sign up next week and data-mine for my ES350 and my GS's LS400 documentation.

[LSPaul]

Once you dig down to that level, the differences will be pretty clear. The temp sensor that drives the temp gauge is a single-wire connector, black casing on it. For the coolant temp sensor that sends signals to the engine ECU, the connector's green in color and is a two-wire connector on both my '93 (now sold) and '94 LSes. Use care in removing the connector, as the plastic's likely a bit on the brittle side and the locking portion will snap off pretty easily.

For the temp gauge issue, you only need to deal with the single-wire/black connector.

Also, for parts numbers, I've had good luck with the site, www.toyodiy.com as a reference source. You'll need to register on the site (a Russian Toyota enthusiast site, for what it's worth) to get access to the parts lookup functions. It's not a proper electronic parts catalog, but it's been accurate for my needs over the last few years.

Most auto parts stores should carry the sensors, no big deal--shouldn't need a part number. Call or check online in advance.

Bring sockets and extensions (mostly 10mm, but also bring a 12, and some deep sockets to remove the temp sensor(s) from the intake manifold, if need be. If I recall correctly, that's either a 17 or 19mm?). If you do have to pull either of the sensors, be prepared to move quickly, as coolant will come out of either opening once you've pulled the sensors.

Best,
Paul

[WeeWun]

Paul, I have subscribed to Toyota/Lexus TIS but do not know how to download. Am not computer illiterate but am stumped on this one.

You advice is necessary, thks.

[LSPaul]

Hi, Walt--

If we're talking about a Windows-flavored computer, do a right-hand mouse click on each file name, then save it to your computer. Usually it'll land in the "documents/downloads" directory. Mac? Don't know, sorry!

Hope this helps--
Paul

[Exhaustgases]

Heres a place to look up parts, I'm not sure how complete this parts book is though. It takes some practice to get to know how to navigate it all.

http://www.lexussouthatlantaparts.com/productSearch.aspx?&ukey_make=1082&ukey_model=15669&ukey_trimlevel=0&ukey_modelRange=0&modelYear=&ukey_category=0&ukey_driveline=0&isOnSale=0&searchTerm=

[WeeWun]

Bob, thks for the input, just what I need.

Paul, I have taken a two day subscription to the Toyota/Lexus TIS site, wow there is a lot of material out there. I thought when I subscribed that I would be able to download the material for our 2014 ES350, my daughter's 2012 Camry and my Grandson's 1992 LS400, was I wrong. I will be lucky to get one vehicle's material collected.

I didn't realize that I would have to categorize the downloads to prevent overlaying. After two restarts I have developed a system, I hope. Time consuming and dull but I can't afford to attention lapse.