93-97 Coolant Temperature Gauge Modification

[NLXTACY]

Woohoo!!! RavenTai, you are the man!
Just did this mod after Moser sent me the parts. Being as I had taken apart the dash a few times already this seemed like old hat. The whole thing took me maybe 20 mins start to finish. The gauge works great now. Its 53º outside right now here in SoCal so the temp gauge reads well below middle. When I do some freeway driving today I can check to see how it goes. One more word of caution, the small plastic indicator strips come off pretty easily. I didn't notice that one of them had slipped from its tiny white plastic posts and now I have a small wedge of light that shows through when I start the truck or when the headlights are on. I need to remedy this but I really dont want to do this yet again

 

[Trailbus]

i've got the parts ready to go.... but the won't let me break anything until I fix the stuff that's broken (like the passenger front window that doesn't work, or the sunroof that doesn't work, or the courtesy lights that don't work....)

Did you order the resistor sizes I posted up? I haven't tried them out (or eve aquired them yet) so you'll be the guinea pig. Hope they work or I'll feel bad.

I got side tracked with building a Sanden AC Compressor OBA setup.
Guess I oughta get them & get busy.

 

[Pinetop Cruiser]

Great work RT! Just finished this mod on a 96 LX450. I've accessed the instrument cluster a couple of times (added diff lock indicator bulbs following an OEM locker retrofit) and just had one more thing to add if people are having difficulty hooking up the wiring connectors to the back of the cluster-- if done carefully so as not to touch the face of the cluster, you may find there's much more room to maneuver the gauges and plug everything back up if you do it BEFORE re-attaching the front plastic bezel.
Again- thanks to all for all the time spent blazing the trail on these mods!
David

 

[sseaman]

any 91-92s yet?

 

[RavenTai]

any 91-92s yet?

There was some talk about it a few posts back but no definitive answers on how well it works.

 

[wearsabrowncoat]

Finally got it done, took me just over two hours but I spent lots of time cleaning stuff while I had it apart. Nice to see the needle move now. I was working out of a hotel room so didn't have all my tools like a vice or a clamp . I ended up securing the soldering iron in its cheap factory stand. This gave me two free hands, one to hold the board and the other to work with.

 

[4x4CPOSEADOG]

There always has to be one and I'm it this time. I've got a '95 cruiser and read and adhered to Rav's directions and just completed the mod as directed and here's what happened. From startup to approximately one mile - city driving - the gauge remained on the cold peg - then all of a sudden it shot up to 2/5 toward the red (not quite half way) back to the cold peg, back up to 2/5, back to cold peg and back again to the 2/5 mark all in about 10/15 seconds after which it remained at the 2/5 mark for 5 or 6 minutes and then it went back down to the cold peg and remained there until I returned home, which was approximately 10 minutes later. Any words of wisdom out there as to what might have went wrong?

Just like 7P's there is always exception and I'm the second one. Me and Mike (mikedamageinc) did this mod yesterday afternoon 12/20/08. We soldered the 110/50 ohm resistors and put everything back up. I cranked the engine and let it idle for about 10 to 15 minutes to warm it up but the needle just stayed on the 2/5 mark and never goes up in the middle where it usually stays in 10 minutes warm up. So I decided to drive it for about 3 miles to see if it goes up at least to the middle part but it did not and it was fluctuating between 2/5 and cold peg. The outside temperature was about 48 to 51 degrees at the time I was driving it.
So the question are:
1. Can I drive the rig for at least two days before I can get back to the resoldering part?
2. Is there any effect to the ECU if it keeps on fluctuating just like what I described above?
3. Is it possible that the resistors we put in are bad resistors?

I resoldered using a lot of flux - slapped her in and the needle jumped right up to 2/5 at startup (engine is still hot) so I think it'll work.

Have you guys heard from 7P's if he get it to work using a lot of flux when he resoldered the resistors?

 

[semlin]

Just like 7P's there is always exception and I'm the second one. Me and Mike (mikedamageinc) did this mod yesterday afternoon 12/20/08. We soldered the 110/50 ohm resistors and put everything back up. I cranked the engine and let it idle for about 10 to 15 minutes to warm it up but the needle just stayed on the 2/5 mark and never goes up in the middle where it usually stays in 10 minutes warm up. So I decided to drive it for about 3 miles to see if it goes up at least to the middle part but it did not and it was fluctuating between 2/5 and cold peg. The outside temperature was about 48 to 51 degrees at the time I was driving it.
So the question are:
1. Can I drive the rig for at least two days before I can get back to the resoldering part?
2. Is there any effect to the ECU if it keeps on fluctuating just like what I described above?
3. Is it possible that the resistors we put in are bad resistors?



Have you guys heard from 7P's if he get it to work using a lot of flux when he resoldered the resistors?

the ecu uses a different temp sensor so no worries there.

it sounds like you have a gauge that works but reads lower than usual. it could be the gauge or the resistors. I would try a different set of resistors, or else borrow a scangauge and calibrate your current reading using the obd2 temperature signal. just remember it is all relative. a significant fluctuation beyond your 2/5 normal is a concern.

 

[7P's]

It worked just fine after I removed the resistors, cleaned everything up and resoldered the resistors back in. I didn't do anything different the second time around except I used about twice as much flux.

 

[RavenTai]

Just like 7P's there is always exception and I'm the second one. Me and Mike (mikedamageinc) did this mod yesterday afternoon 12/20/08. We soldered the 110/50 ohm resistors and put everything back up. I cranked the engine and let it idle for about 10 to 15 minutes to warm it up but the needle just stayed on the 2/5 mark and never goes up in the middle where it usually stays in 10 minutes warm up. So I decided to drive it for about 3 miles to see if it goes up at least to the middle part but it did not and it was fluctuating between 2/5 and cold peg. The outside temperature was about 48 to 51 degrees at the time I was driving it.
So the question are:
1. Can I drive the rig for at least two days before I can get back to the resoldering part?
2. Is there any effect to the ECU if it keeps on fluctuating just like what I described above?
3. Is it possible that the resistors we put in are bad resistors?



Have you guys heard from 7P's if he get it to work using a lot of flux when he resoldered the resistors?

1. sure no problem, should just be an indication problem (or maybe not see below)

2. no as Semlin said the ECU has its own sensor on a separate circuit.

3. Bad resistors I guess could be one possibility, did you buy the mil spec ones from the link at the beginning? we are paying a lot for resistors relative to the price of common resistors, one of the reasons (besides accuracy) being they are suppose to be quite reliable. if you have or can borrow a meter you can measure the resistance of the resistors once removed from the board.

Another possibility is your motor may actually be running a bit cold, thermostat sticking open? I don't have my notes handy but I am pretty sure the two fifths mark on a modified gauge would have been well within the center dead zone on the stock gauge, if it is cold it could have been cold for quite some time and you would not have kn ow it, As Semlin said if you have acces to a scan gauge that would tell us quite a bit, if you have an IR thermometer you can put a spot or black paint on the outlet neck next the the distributor and get a reading ( bare aluminum gives odd readings)

if you take it back out check look at your solder joints, they should be shinney & smooth.

a "cold joint" and several other defects will have a crunchy aluminum foil appearance

you should also check the connections with a meter, resistance across the joint should be less than 1 ohm


rosin/flux core solder should be all the flux you need, make sure there is no oil in the are (even your skin oils can cause problems) if the solder is not flowing you may want to degrease the area (be careful not to get anything on the face card of the gauge)

 

[mikedamageinc]

I believe the resistors are in the correct places and the solders were smooth and shiny, the only thing i can think of is that maybe we should have scraped the foil run to get a good connection, especially the one that replaced the diode and placed on the opposite side, it might not be making good contact on both leads. I would like to look at the gauge again, are you off Monday or Tuesday Noel?

The resistors used are the mil spec recommended in the earlier post. I used the same on both of my cruisers. One reads in the middle like normal and the other reads a little over half and will move up to 3/4 sometimes even when driving down the highway with no load. I have a new thermo and fluid, and radiator is in good shape and fan appears to be working.

 

[4x4CPOSEADOG]

I believe the resistors are in the correct places and the solders were smooth and shiny, the only thing i can think of is that maybe we should have scraped the foil run to get a good connection, especially the one that replaced the diode and placed on the opposite side, it might not be making good contact on both leads. I would like to look at the gauge again, are you off Monday or Tuesday Noel?

The resistors used are the mil spec recommended in the earlier post. I used the same on both of my cruisers. One reads in the middle like normal and the other reads a little over half and will move up to 3/4 sometimes even when driving down the highway with no load. I have a new thermo and fluid, and radiator is in good shape and fan appears to be working.

Mike, we can do it Tuesday afternoon or Wednesday morning and I know it won't take that long. I have a feeling that your are right that is not making good contact due to a bad connection. I did not even got the chance to work on the gauge today because I was dragged to go shopping by the and became the . I'll get some soft wire brush and more flux so we can solder it real good

Raventai, semlin, and 7P's, we will get back with you and post the results once we clean and resolder for the second time. The second time should be easy

 

[RavenTai]

yes it gets quicker every time you pull out the cluster. let us know what you find out.

Maybe we should come up with some kind of electrical check to do while the gauge is still out so people can catch problems like that? do most people have access to a meter?

 

[roughlux]

Hi guys. Will this mod work with an 80 series that has the 1HD-T in it? I know there was a very similar gague mod for the surf temp gauges so maybe Toyota used the same if not very similar senders and gauges in a similar era of vehicles? Oh the 1HD-T is a diesel by the way. Cheers.

 

[gbell210]

If someone has any extra resistors, can you PM me? I'd gladly pay one of you, otherwise I'll have to look around Mouser to find out what other goodies I might need to justify shipping. Thanks

 

[Cruiserdrew]

I have extra resistors. Send me a PM with an address and I'll send you the 2 you need.

 

[RavenTai]

Hi guys. Will this mod work with an 80 series that has the 1HD-T in it? I know there was a very similar gague mod for the surf temp gauges so maybe Toyota used the same if not very similar senders and gauges in a similar era of vehicles? Oh the 1HD-T is a diesel by the way. Cheers.

That discussion is better suited for the other thread, I replied to you there

https://forum.ih8mud.com/80-series-tech/53142-adding-coolant-temp-gauge-8.html#post3988397

 

[4x4CPOSEADOG]

1. sure no problem, should just be an indication problem (or maybe not see below)

2. no as Semlin said the ECU has its own sensor on a separate circuit.

3. Bad resistors I guess could be one possibility, did you buy the mil spec ones from the link at the beginning? we are paying a lot for resistors relative to the price of common resistors, one of the reasons (besides accuracy) being they are suppose to be quite reliable. if you have or can borrow a meter you can measure the resistance of the resistors once removed from the board.

Another possibility is your motor may actually be running a bit cold, thermostat sticking open? I don't have my notes handy but I am pretty sure the two fifths mark on a modified gauge would have been well within the center dead zone on the stock gauge, if it is cold it could have been cold for quite some time and you would not have kn ow it, As Semlin said if you have acces to a scan gauge that would tell us quite a bit, if you have an IR thermometer you can put a spot or black paint on the outlet neck next the the distributor and get a reading ( bare aluminum gives odd readings)

if you take it back out check look at your solder joints, they should be shinney & smooth.

a "cold joint" and several other defects will have a crunchy aluminum foil appearance

you should also check the connections with a meter, resistance across the joint should be less than 1 ohm


rosin/flux core solder should be all the flux you need, make sure there is no oil in the are (even your skin oils can cause problems) if the solder is not flowing you may want to degrease the area (be careful not to get anything on the face card of the gauge)

I took the instrument cluster back out for the second time and put in more solder/flux at the joints to make sure the connection is good. Then installed it back for test drive. After about 7 or 8 miles the temp guage needle just stayed at the cold mark and never even got to the middle part where it is usually stay with the OEM resistor/diode.

Mike (thanks mikedamageinc) came by and gave me a couple more resistors (110 and 50 ohms). I removed the instrument cluster for the third time (I'm getting good at it now) to take the temp guage out. This time I decided to take it to work and let the Navy aviation electronic technicians who work on Micro-Miniature (2M) to do the soldering for me since their workshop has a controlled temperature and they got some hi-tech soldering equipment with electro-static discharge wristband. The technician did an outstanding job in desoldering, cleaning, and re-soldering the resistors to the board. Using a Fluke meter, we checked the same resistors that was previously installed and they were good showing a 110 ohms and 50 ohms reading in the digital fluke meter. So I decided to use the same resistors.

Went back home, installed the temp guage back to the cluster and then installed it to the truck. Crank it back up and went for a test drive. Lo and behold, the needle started to rise just above the cold mark and after about 8 miles or so, the needle stayed below the middle part. After driving for about 16 miles the needle goes slightly above the middle part, and this happen when I was on a stoplight with an outside temperature of 48*F. So everything went well and the temp gauge is now working great!

We will see what it does in summer. Lessons learned on my issues were:

1. Soldering iron is not hot enough.
2. Garage room temperature is 55* where the solder quickly gets cold.
3. Too much paste flux is not good.
4. Always disconnect the negative battery cable when working on electrical/electronic equipment.

Thanks to Raventai for an outstanding R&D temp guage mod. an Thanks mucho to Mike for the resistors

Post is useless without pictures, right? So here they are in numerical order.
1. resistors connection
2. soldering gear with new chopping board as clamping station
3. temp guage in cold mark after 8 miles of driving
4. 110 and 50 ohms resistors
5. smooth and shiny solders
6. temp guage at just below the middle part
7. temp gauge needle at stoplight

Again, many thanks to RT and semlin. You guys rock!

 

[4x4CPOSEADOG]

next pictures on the list.

 

[4x4CPOSEADOG]

last pictures on the list. This picture taken while on the stoplight. Thanks RT.

Happy New Year to all!