93-97 Coolant Temperature Gauge Modification (1 Viewer)

[treerootCO]

Just finished the mod thanks to Uncle Ben for the parts and of course this thread.

Also made the gauge a little more sporty while I was in there

 

[Beowulf]

OK, somebody will ask for details so let it be me. Also, how did you get both directionals on at the same time?

-B-

 

[treerootCO]

OK, somebody will ask for details so let it be me. Also, how did you get both directionals on at the same time?

-B-

www.whitegauges.net

The kit is almost perfect but the oil gauge isn't correct for '95. Hazards and good timing for the night pic. I think I'll change the lights from green to blue LEDs for a touch more style.

 

[semlin]

i can't find the lc on their website. have you a link?

 

[Trailbus]

I finally took the reigns on the 91-92 mod thanks to GinericLC having a cluster layin' around. The gage printed circuit card is configured just like the 93-94 card.

After removing the zenor diode & resister, I hooked it up like I thought it should be but the needle didn't move.

RavenTai & Semlin, I connected +14.4V to the circuit card "IGN" post, the terminal on the temp sender to the "-" post and connected the base of the temp sender to power supply - terminal. In place of the old components, I have 2 variable high power decade boxes(~110 & 50 ohms). Where did I go wrong?

 

[RavenTai]

can you post a pic of the back of the gauge?

 

[semlin]

I finally took the reigns on the 91-92 mod thanks to GinericLC having a cluster layin' around. The gage printed circuit card is configured just like the 93-94 card.

After removing the zenor diode & resister, I hooked it up like I thought it should be but the needle didn't move.

RavenTai & Semlin, I connected +14.4V to the circuit card "IGN" post, the terminal on the temp sender to the "-" post and connected the base of the temp sender to power supply - terminal. In place of the old components, I have 2 variable high power decade boxes(~110 & 50 ohms). Where did I go wrong?

i don't get why you are wiring it directly instead of plugging it back into the dash cluster. are you trying to test bed it out of the truck?

 

[RavenTai]

Semlin, He is doing a 91/92 gauge, IIRC both the gauge and the sender have different part numbers from 93/94 and 95-97, It seams reasonable to test it out of the truck in controlled condition for the first of its kind,

Trailbus I do not think you hooked it up properly,

on the 93-97:


14.x V+ goes to the IGN post, this part you got right,

ground from power supply goes to both the base of the sender and to the "-" post of the gauge, the sender sense does not go here,


the sender "sense line" hooks to the unmarked post near the resistor, not the - post,

I woudl like to see a pic of it to be sure we are on the same page,

here are two schematics, the hand drawn was when I was first figuring out the layout, it is in a similar form as looking at the back of the gauge and has notes to the three connection pins from the EWD for a 96, doubt those will be any good for a 91, but the layout should help you get a sense of the circuit. there is also a fourth connection to the outside for the oil pressure gauge,

The other is a purely schematic view of the same thing,

L1, L2 & L3 are the coils of the "air core motor" that drives the needle

R1 is the resistor of the gauge that is replaced with the 110 ohm resistor,

R2 is the variable resistor of the sender

D1 zener diode is replaced with the 50 ohm resistor in the mod

 

[Trailbus]

Ah, I get it now. I skipped by all the "bridge talk" earlier in this and the devolpment threads. My memory was getting garbled after trying to take in 13+ pages of info.

The part number of the board is 769902-961 and the resistor color codes are Violet, Green, Black, Gold just like the 93-94 (like in this post IH8MUD.com Forum - View Single Post - Adding coolant temp gauge?). The only difference I can see is the face plate part number is 769039-373.

I'm not sure if the sender is the same for these years but a few of the ones on partsamerica.com cover like from '88 to '97.

I'll head back to work & see if I can get it to work like you said. I was just about to tear into my dash to test this cluster out.

Anybody know what the "danger zone" for the tractor engine is? I'd think it would be higher than those newfangled mismatched metal engins most of you have. The thermostat for the 3FE os 88*C (191*F)

 

[RavenTai]

According to CDan the part numbers of the senders follow a 91/92 and 93-97 grouping, basically the part numbers are different for the different motors, they could be the same sender electrically just in a different form like thread diameter or connector style. In the other thread I talk about the markings on the 1FZ sender, woudl be interesting to compare them to the 3FE sender. what we need to know is weather the 3fe senders resistance/ temperature curve will be the same as the 1FZ sender.

The thermostat for the 1FZ is a bit lower, 82C, I will not hazard a guess as to the danger zone of the 3FE, but I will come at that question from another angle, if your coolant temperature rises considerably above thermostat opening temp you know the cooling system is not under control and there are cooling system issues.

 

[Trailbus]

I just finished messing around with it more, I'll have to sort through the pictures, shrink, & post them up later.

Here is the 3FE sender. The only markings on it is a triangle on one of the flats, "OJ" on the next one, and a dimple pressted int the next. I guess i should've taken a few resistance readings while I had it set up.

In stock form, 208* indicated just below center and 225* was just above center. It's really hard to get a picture that truly represents what the eye see's. I started out using a dry-well and ended up with 244* at the bottom of the red. I need to go back & recheck the upperscale in the wet bath.

It sucks I can't get to Mud at work (Air Force Comm Nazis blocked it ) and I don't have the equipment at home (10 miles one way). I'm off all week but can't work on it while they are open for business.

 

[Trailbus]

OK, I think I might have it. Hooked the gage up with variable resistors & here is what I got:

Using 83.2 Ohm in place of the 75 and 12.1 Ohms in place of the Zener diode

Needle at to edge of bottom mark 175*
Centered between bottom mark & bottom of red 196.5*
Center of overall scale 201*
Bottom edge of red 220*
Center of red 230*
Pegged 249.2*

I measured the resistance of a piece of wire I had laying around & got .03 Ohms/foot (yes it was Toyota wire). If you figure 10 ft from the gage to sender, that .3 ohms probably screwed your initial math up and caused the variance from the test bench to dash.

I did notice a few things in the process:

1. In stock configuration, the current draw varied when the zener kicked in. Draw started at .21 amps and kicked up ti .35 amps which caused my voltage to jump from 14.4 to 14.6 volts. Probably not an issue when installed & on the trucks battery, but changed my readings slightly when using a bench top power supply.

2. Gage hysteresis is terrible. Going downscale, (hot to cold) readings changed by a 1/16th of an inch. removed and reapplied power to get repeatability. Also not an issue if bouncing down a gravel road, but if stopped waiting for the motor to cool down, it might be slightly cooler than you think. Normal practice in the calibration of pressure gages is to "lightly tap" the face to eleviate hysteresis. Probably don't want to do that in the cruiser as it might reactivate your "D" light:shotts:.

I'm going to try to score some resisters in Boise tomorrow. Then it's time to tear into my dash. Which, opens up a can of worms for me. While in there, I'll swap my ARB switches to the curved rear defroster ones & add custom lights to the bottom of the cluster--Vote now

 

[RavenTai]

I noticed a difference going up vs going back down, it was a lag in heat reaching the core of the thermistor, if you heat the thermistor and watch its resistance alone you will notice it lags, I always heated to the highest temp I wanted to read and then watched it as it cooled down, that seamed to give the best accuracy.

The resistance of the circuit goes down as the temperature of the thermistor increases and so the amperage will increase, the R1 resistor gets quite hot from the current when reading high temps.

 

[semlin]

i noticed the lag coming back down in the photos of the 93 gauge, but in real world conditions the gauge seems very responsive in both directions. If I crest a hill that has bumped me up and head downhill, I will see a correction in seconds.

Greg, if you would like the bench test photos of the 93 gauge through the full temp range for comparison purposes shoot me a pm with an email addy. My initial reaction without going back to check is that you are about 6-8 degrees hotter at any given point.

 

[Trailbus]

No go on getting resistors in Boise, guess I'll have to order some.

To be continued.......

 

[RavenTai]

No go on getting resistors in Boise, guess I'll have to order some.

To be continued.......

I looked locally for resistors also, and had no luck, I can get 1/4 and half watt resistors all over but 3 watt was non existent especially in odd values, there were some 5w arround but they have bulky heat sinks on them, woudl be a lot of work to get them in the gauge,

Check out the resistors at the start of this post they are very good, 1% accuracy, wire wound instead of carbon, mil spec ratings, etc,

 

[Cruiserdrew]

Back to the top with a thank you to Raven Tai and to TrickyT. Tom was at my house yesterday to install the new suspension on his 80. Afterwards he asked if I wanted to do the temp gauge mod.

So we did! Actually, he did the soldering. Disassembling the dash is a pain, but doable. I also got to replace the burned out "D" light in the cluster.

I was actually surprised how flimsy the instrument cluster and gauge parts really are. It's all lightweight brittle feeling plastic. Bottom line, be careful when you pull ot the cluster!

The temp gauge now does vary-reads about 1/3 in normal cruise, just over 1/2 on a long steep freeway climb at full throttle. Next step is to calibrate the gauge with a Scangauge.

Gracias.

 

[plmont]

Thanks for sharing your knowledge Raven. I completed this mod recently and it was great to see movement in the dead region...much needed piece of mind.

Kudos to the members of this forum, you are an ingenious lot. The information is endless and the opportunities to improve on an already legendary vehicle are almost infinite...definitely nervana for the gearhead... Paul

 

[RavenTai]

Two more actual usable gauges out there,


Have any more 91/92 guys tried this out?

 

[sandcruiser]

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....)