93-97 Coolant Temperature Gauge Modification

[Mr.Bryan]

Yup, I did it a few weeks ago. It's a cool mod! thanks for the write up, it only took me about 35 min. to do.

My temp gauge has been moving all over the place. I've noticed with ambiant temps around 80-85 out, ac on and at about 65-70mph i'm about 2-3 needls widths away from red, but if I kick the ac off it drops down a bit. I'm going to try flushing out my system in about 2 weeks and I'll see if that makes a diffrence. Actually I think I'm going to tear the whole front end down and flush everything out. I think i've got mud between my condenser and the radiator. Damn Ih8mud!

 

[RavenTai]

Cool let us know if that helps.

 

[Gauge]

Shamefully, I am only getting around to doing this mod now after purchasing the resistors - what seemed like a year ago. Completed it this weekend actually without a hitch.

First off I want to give a BIG THANKS to Raven Tai for doing all the work on this mod. I remember when he was doing the testing and reading his every post, as his progress developed - most of it electrical mumbo jumbo, at least to me anyway. His instructions were great and saved me much time, effort, and most likely a broken dash if I had to figure out how to dissamble the thing myself.

I have not driven my rig much after the install, but I have noticed that the gauge is MUCH more responsive. With the AC on and driving agressively, the temp gauge reached the 3/4 mark - something I have neve seen before in my years of driving. Actually it was quite disappointing to see how easily I could make this engine "hot" with little more than the AC on and some agressive driving on a cool spring day in May. I am afraid to see what will happen in August. No wonder Toyota installed the "zener diode". Probably cheaper than installing a larger radiator.

The 80 series engine has an iron block and an aluminum head. These metals expand and contract at different temperatures and the head gasket has to work especially hard to try and seal together two surfaces that are expanding and contracting at different rates. In my opinion, this is why these engines are prone to head gasket failure. Having a properly working temp gauge is a MUST to monitor temperatures and adjust your driving BEFORE temperatures reach their maximum and the head gasket has blown.

Raven Tai we all owe you BIG TIME for this. If you are ever in Philadelphia, look me up - dinner and drinks are on me.

Cheers!

 

[semlin]

I have not driven my rig much after the install, but I have noticed that the gauge is MUCH more responsive. With the AC on and driving agressively, the temp gauge reached the 3/4 mark - something I have neve seen before in my years of driving. Actually it was quite disappointing to see how easily I could make this engine "hot" with little more than the AC on and some agressive driving on a cool spring day in May.

just think of the engine temperature as being highly responsive to environmental t stimuli. it sounds better. funny that landtank does not get this kind of fluctuation. what is his secret i wonder? you might think he lives in aplace that is mostly flat as a board with no a/c use until late spring

 

[Mr.Bryan]

well, I got all the crap out of my condenser and radiatior, and I had my whole system power flushed and new toyota red put in and it runs a tad bit cooler. Not too much diffrence but the needle doesnt get more then 3 needle widths from the bottom of the red w/ ac on and in traffic so I'm happy. Thanks again ravan tai

 

[RavenTai]

Raven Tai we all owe you BIG TIME for this. If you are ever in Philadelphia, look me up - dinner and drinks are on me.

Cheers!

Thanks that sounds like a good time,



I have learned a lot about my beloved cruiser from everyone here, this was something I wanted for my truck & I had a good time figuring it out I knew others would be interested also. feels good to give something back

it is interesting that many trucks pop up in temp so easily, mine does the same but as we have moved into warmer weather mien has not popped up any higher that it did in cooler weather, it does go up with AC use when idling or in traffic but mien seams that once it hits a certain point (~205) it never goes any further. But it has been an unusually cool spring here, rarely in to the 90's, we will see what it does in lower triple digits with 90%+ humidity. If it goes up much more I am going to look into cooling system improvements,

I am moving to a hotter more humid environment in a few months, I will really need it then.

 

[ashooter]

Has anybody figured out anything on this mod with regards to a 91-92 truck with a 3F-E yet?

If this temp gauge problem is a (the?) cause of the FZJ's head gasket failures, might it be reasonable to assume that FJ's temp gauge works better, since they don't apparently have the same HG problem? I admit I am almost a complete mechanical idgit, and I know even less about electrickery, so I may be reaching with that guess.

 

[semlin]

91-92 has a cast iron head so much less chance of blown head gasket. the temp gauge does appear to be "numbed" from my experience. it has a different part # and a different sender part number so someone would have to pull one and post photos. the 93-94 had a different part no. to the 95-97 gauge but was virtually identical.

 

[ashooter]

semlin,

Not likely to blow a HG, but it could still be getting plenty hot and not show anything exciting on the gauge, huh? Hmm... I will keep and eye out for somebody more technically savvy than me to dig into a 91/92 and see what they find out.

 

[semlin]

if you just pull the gauge and photograph it then put it back, there is a good chance we can tell you if the mod will work. pulling the gauge is a 1/2 banana job that takes 20 minutes each way.

 

[RCFloyd]

Hey folks,

The last time that I read through this thread, no one had performed this mod on a 93-94 rig. Has anything changed, or do I need to be the guinea pig?

Robert

 

[semlin]

i have it in my 93. Read raventai's posts for the temp readings. It seems to be slightly cooler at the red than the 95-97 with the same mod.

 

[Biff]

Anybody want to sell an extra pair of resistors, damm shipping is to expensive at the store.

 

[semlin]

i have a set. i can mail them from canada if you pm me your address. they will arrive in about ten days unless your border guards blow them up. you will have to thank raventai for them

 

[RCFloyd]

Parts ordered... Got an extra set for someone out my way...

Robert

 

[ashooter]

if you just pull the gauge and photograph it then put it back, there is a good chance we can tell you if the mod will work. pulling the gauge is a 1/2 banana job that takes 20 minutes each way.

I have a long list of to-do's already, but when I get time, I will pull it and take some pics if nobody else gets around to it first.

 

[7P's]

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?

 

[cary]

My guess is you didn't get a good solder connection. Go back and resolder the board connections. You didn't get the board really hot by accident did you? 50 watt soldering gun or something like that? If you did, could be the board got overheated. Someone with better solder/electronic skills will likely chime in with an answer soon.

 

[Mr.Bryan]

loose connection maybe? Not soldered good enough? (not knocking you or anything) resistors grounding out on something else? Bad resistor?

 

[RavenTai]

It does sound like a bad connection, I am afraid you are going to have to go back in. fortunatly it is much quicker the second time,

check your solder points, they should look shinny and smooth, a crackeled or modeld or flat looking surface indicates a cold solder joint, one tip on soldering you want to get the iron as hot as it will get, heat the joint area and then take the heat away in a smooth short ammount of time, as you are melting solder your iron is getting colder and the board hotter, you want to get the joint hot before ecerything arroudn it gets overheated, the quicker you are the better,


and also check the screws that mount the gauge to the cluster, also inspect the plugs into the cluster, and generally look everything over for good contact

if you are good with electronics you could test it outside of the cluster using voltage from your battery and 2 watt potensiometer as a synthetic temperature sensor,

testing is what the calibration resistors were all about, I never have gotten to that part as it has been good for everyone so far and it would have been an added expense for everyone, I should have known that there would be troubleshooting to do eventually and I have not prepared, sorry by bad,

If you cannot get it figured out let me know, do you have a meter?