Adding coolant temp gauge?

KliersLC · 10-22-07, 01:06 AM

My aux fan runs off a dual input controller--one side for the compressor, and the other side on a temp probe in the radiator. This would suit your purposes I think.....

sandcruiser · 10-22-07, 10:56 AM

Yep. That's the basic idea I'm looking for.
Just gotta figure out the wiring.

I prefer not to add more components, if I can use what's already there. Getting stuff down here is often more difficult than just working with what I've already got.

Quote:

Originally Posted by KliersLC

My aux fan runs off a dual input controller--one side for the compressor, and the other side on a temp probe in the radiator. This would suit your purposes I think.....

KliersLC · 10-22-07, 11:27 AM

The controller is 34.99 at autozone and will fit in a pocket......

sandcruiser · 10-22-07, 12:07 PM

So here's my thoughts on the Aux fan wiring. And Idiot light.

Run power from battery + to a fuse to the fan +.

Then have two circuits to create a ground connection from the fan. ie: the GRND from the fan goes to two Normally Open relays.

Relay 1 (A/C clutch circuit):
Pole 30: to ground terminal from fan.
Pole 87: GRND
Pole 85: to + connection A/C compressor
Pole 86: GRND

Relay 2 (overheat circuit):
Pole 30: to pole 30 on relay 1 (to ground from fan)
Pole 87: GRND
Pole 85: fused + from battery
Pole 86: to pin 1 on A/C cut out switch (which also grounds A/C cut relay per RavenTai's description) & to ground on red LED (dash idiot light)

Idiot Light: + from fused source ---> Light ---> Pole 86 on Relay 2/pin 1 on Cutout S/W.

End result is that under normal operation, the fan is off. If/when the engine coolant temp exceeds 226, the Fan is activated (even if the motor is turned off) and the red LED in the cluster is activated (Question: is there a factory idiot light that can make sense here?).

Independent of the above-- whenever the A/C clutch is activated, the fan is on as well. When the compressor is off, the fan is off. It would be even better to have another thermistor involved such that the fan will not turn on if the temp is below a certain cutoff, just to save some juice while the motor is warming up... but that project will have to wait for another day as it just isn't that crucial. If there is some stock sensor that I can wire in... that would be interesting.

Thoughts?

ps: Sorry for the semi-hijack, but it is related to the idiot light mod.

Quote:

Originally Posted by RavenTai

on my 96

The temp switch connector has two pins

pin 1 green with yellow stripe leads to a normally closed relay that interrupts the AC clutch power when the overheat switch activates.
pin 2 white with black stripe is a ground,

If you connected the ground end of your alarm to pin 1 it would see
nothing when ac is off
battery + when the ac is on
and ground when the switch hits 226.

only remaining question is how much current overhead the switch has, an LED should be no problem, a large buzzer or incandescent light might, ifyou wanted to run something with any meaningful current draw a realy could be used to take the load off the switch ( with is how it is used stock)

KliersLC · 10-22-07, 01:21 PM

THe only problem that I can see, is that your fan will shut off when the temp goes below 226. Ideally it would stay on until you get down to 195 or so.....

sandcruiser · 10-22-07, 01:45 PM

Actually, the sensor will turn the fan on at 226, then off at 217. It would be even better if it would stay on until a lower temperature. I'm going to go with the Toyota engineers, however. They apparently figured that when the temp drops below 217, it was ok to let the occupants enjoy A/C again...

I figure that if/when the temp gets that high, I'll know enough to turn the A/C off manually and/or get my foot out of it, and/or turn on the heater and/or pull over to let things cool down. Having the more accurate temperature guage will help with this.

If someone else is driving, 217 isn't ideal, but it isn't going to pooch the motor if it happens once a year (I hope!). And having the fan come on at 226 sure beats not having it come on at all. It also eliminates what I see as a failure in the stock system--- as it stands now, when the A/C cutout cuts out, the fan actually turns OFF! Which is obviously not the ideal behavior.

Perhaps at a later date I could incorporate some other sensor with a broader range. I'd rather see it come on at 220 and go off at 200.... but for the time being, this mod is easy as it doesn't require any special parts (just two relays that I've already got) and it is easy enough to modify more, later.

Edit: I think I'm going to use the A/T Temperature light.... as my indicator. Anyone know what that actually looks like?

semlin · 10-22-07, 06:30 PM

217 is not right for a gasser, can't speak to a diesel. if you are that high chances are you will spike right back up and your engine will be in the danger zone continuously. i'd want to get down to 200 minimum before it cycled off to at least be in the green zone part of the time. even better i'd just rig a hardwire override switch

sandcruiser · 10-22-07, 08:42 PM

Semlin: I agree that hardwiring an override switch in is a good idea. Very inexpensive, not a difficult circuit. Can add it to the system easily.

Unfortunately, from what I read, the diesels are less tolerant of overheating than the gassers. :(

Keep in mind- I don't plan on **Ever** having it spike into the overheat fan territory. I'm not trying to fix an overheating problem here. I'm trying to create a simple, almost free solution to help minimize the damage done in a bad situation.

My thinking is, that for the cost of adding a single relay (what, $4?) I can create a simple system that could help make a "Disaster" into a "Oh, that was bad". That's all.

I agree--- setting up the switch such that the fan kicks in at 220 and kicks out at 200 would be better. At some future point I've got the option of sourcing a different switch that behaves in such a manner.

Someone said earlier on this thread: "Perfection is the enemy of good enough." Seems a good quote.

In reality- I'm having a very hard time envisioning a situation in which the motor is likely to overheat and the A/C is off. If the A/C is on, then the Aux fan is already on. So, in essence, I guess that what I'm really doing here is that I'm setting it up such that the fan *stays* on, even if the A/C gets cut out by the A/C cutout switch.

Sorry if this comes across scrappy. I'm a little bummed at the lackluster enthusiasm surrounding a virtually free, super-easy mod that adds (admittedly imperfect) protection to the cooling system. I thought it was a pretty cool idea (no pun intended).

Ok. Hijack over. Back to our regularly scheduled Gauge modding.

KliersLC · 10-22-07, 09:45 PM

We aren't unenthusiastic, just trying to make something work as well as it can. Your AC on scenario has one flaw, the condenser will be dumping heat in front of the radiator if the AC is running. Your aux fan will make your AC run cooler, but will do very very little for your radiator temps.

semlin · 10-23-07, 10:53 AM

i don't know costa rica weather but the 80 engine bay is a giant heat sink so if you get into very hot weather and things are not running just right you can get into an overheating feedback loop. for example, a pinhole hose/rad leak or a bad rad cap. the system needs pressure to cool.

semlin · 10-23-07, 10:53 AM

but yes, something is definitely better than nothing.

sandcruiser · 10-24-07, 09:17 AM

all except the relevant part- the idiot light. :(
If i hook it up as I've indicated (previous post) then the idiot light will come on whenever the fan is on. Which isn't what I want it to do.
rats.

edit: ok, if the idiot light ground goes through pin 1 of the cutout s/w instead of pin 30 of the relay, then all is well. I don't think that the s/w will have any trouble the very small increase in current.

MoGas · 07-08-08, 10:17 PM

Summer time BTT.........

JO MAOMA · 07-08-08, 10:20 PM

holly post resurection! i just did this today...

RavenTai · 12-22-08, 11:38 PM

Quote:

Originally Posted by 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.

I have not heard of anyone trying it,

Does any one even know if the diesel gauge has the numb range? I would first remove the gauge and see if it has this.

It translates as "middle temperature stable" http://forum.ih8mud.com/chit-chat-se...ate-kanji.html

If so then it needs to be modified, would also be interesting to see if any of the part numbers match up and if the layout and components are the same, IH8MUD Forums - View Single Post - Adding coolant temp gauge?

also if the resistor is 75 ohms that would be a big clue that it is calibrated the same.