Pre heat in BJ74

[Stone]

Mine ain't I cut the wire as in the diagram posted by Mike.

I assume the "glow screen" that I have seen mentioned here, is in fact the pre-heat ( it has pre heat written on it ) plastic thing under the other plastic thing that has " filter " written on it on the right hand side of the steering wheel. ( the big round turney thing that I hold on to when I am driving)

Okay, Mr. Smarty Pants...I don't know why Toyota would use two different coloured wires for the same function in the exact same vehicle (doesn't make sense to me)...but if you say it is then so be it. You haven't inspired me to take the screws out of my glove box to check for you. Have fun with the Arctic blast...there's another one coming after this current one is finished.

 

[Stickboy]

this is getting interesting....
here's that pic from the previous glowscreen thread.... the wire the switch is in is exactly as stone describes much clearer than i did....
i think i'd be a little hesitant of tapping into the actual glowscreen relays. I don't worry about my skill of operation just all those who drive my cruiser unexpectedly.... i've had every kind of diesel vehicle in the past 10 years you can imagine and for some reason the concept of glowplugs/screens and timers is REALLY hard for many people to grasp who drive gassers....

my .03
-mike

 

[NStimac]

What about???

1. So will this work while the truck is running? (Will I be able to smooth out a ruff idle in the morning by pushing the button for a few seconds)

2. Why not get a really big switch and short the whole system as a fail-safe so you can still glow even if critical part fails? What’s the down side to this?

3. Do you think fooling the timer would cause any additional wear since they’re prone to failure anyways?


-Noah

 

[Stone]

1. So will this work while the truck is running? (Will I be able to smooth out a ruff idle in the morning by pushing the button for a few seconds)

-It shouldn't work with the truck running...unless something's wrong.

2. Why not get a really big switch and short the whole system as a fail-safe so you can still glow even if critical part fails? What’s the down side to this?

-I don't like running wires and switches to something that draws that many amps...not a good idea in my books. Wires that carry that much current are usually very large and kept as short as possible.

3. Do you think fooling the timer would cause any additional wear since they’re prone to failure anyways?

-I don't think so...
-Noah

 

[lumpy70]

I think it will work with the truck running. You are fooling the relay into thinking that the temp sensor is turning it on. No worries. Extra wear? No worries. If/when your system does crap out, that's the time when you bypass the entire system to turn it on, like what I've got on my 70.

The switch/button wire that you would run is in essence a signal wire. All it is doing is closing the relay, carrying very few amps. The yellow wire that you are tapping into is serving the same function as the button you are going to put in, and it is probably a #14 or a #16. The wires on the contacts on the relay itself are most likely coming off of the battery and at any rate is rated for that many amps.

I'd be surprized if the control wire to the button on mine is carrying as much as .2 amps...yes .2 The wire to and from the relay is carrying 47 amps, so it is nessesarily bigger.

 

[Stone]

I understood his question to be referring to the actual glow screen relays (the mondo ones on the fender), and not the glow timer. You can still trip those manually by splicing into the coil wires, and that wouldn't carry much current, but bypassing them by hooking up current to the load side for the glow screen (which is what I thought he was referring to on question 2), is not advisable...IMO.

 

[crushers]

i don't think trying to ignite the glow screen after the truck is running would be a good thing, if you burn out a glow plug or 2 you can buy replacements for $20 +/- burn out a glow screen and it will much more expensive...
if it is running rough then shut it down and do a "cold" cycle again.
well that is my suggestion that is...
happy holidays

 

[Mick]

I now know that the "glow screen" is not the screen that lights up when the pre heat system is operating. ( this was really confusing me ) Anyway I called a guy who has the gear to test the system in my vehicle and he sujested I bring it over in the new year. I could not see the point of instaling an over ride switch until the system was working.

When I went to start the engine today, I noticed a "Ding" sound when I turned on the ignition, I turned it off and on again, and it did it again! It was -16 and I assumed that this ding sound was an audible signal that the pre heat syatem was working, but the "pre heat " light was still not on. I left the ignition switched on for ten seconds before starting the engine and it fired up straight away.

Is my pre heat system now working ?

Thanks

Mick

 

[Stone]

Mick: When you heard that sound, did it sound like a relay clicking? Also, did you notice the needle on your dash voltmeter drop after you heard the sound? The glow system uses a lot of current and will cause a noticable drop in the voltmeter while it's working. If the needle on your voltmeter dropped down, then your glow screen is probably kicking in.

I guess what you're confused about is that the "pre-heat" indicator on the dash is not lighting up at the same time that you hear this sound prior to starting the engine? When you remove that square green connector (temp sensor) beside the temp sender and turn the key to "on", the "pre-heat" indicator light still doesn't come on?...and do you then also hear this sound?

 

[Mick]

Hi Stone


Yes it did sound like a relay clicking in, it can clearly be heard. My old woman describes it as it sounding like a spring twanging. The voltmeter needle stays in the white all the time although there is a noticeable difference when the engine is running.
The pre heat dash light is not lighting up at all and it never has done, the" Ding" sound is a new thing.

When I had previously removed the green sensor plug I did not notice the sound the sound.

I think the only way to find out what is going on for sure is to get the system checked out properly, I will get this done soon.

 

[Stone]

Hi Mick: According to what you have described, then your glow screen is probably not working right now, and I'm not sure what's making that sound that you describe.

You changed the light bulb in the dash, so we know that one works. You tried to disconnect the temp sensor to fool the glow system to come on but nothing happened, so I would try looking at the glow timer and the glow relays themselves as my primary suspects.

According to the FSM diagram, you pre-heat system should be fused on the "engine"15A and a fusible link on pin 6 of the glow timer harness. I would first make sure that those two are in good order and that the glow timer is receiving voltage. Next, the glow relays themselves have a fusible link on the battery lead to the relays...GLOW 2.0L. Check that to make sure that your relays are getting voltage.

If everything checks out so far, my next course of action would be to take out the glow relays (remove the ground cable from the batteries first) and check their operation. If you supply voltage to the coil leads, they should flip the switch inside and your ohm meter should show zero ohms on the load contacts of the relays. If this checks out, then I would suspect that your timer is the culprit.

I am fairly new to this, but this is what my instinct tells me to do...so I guess take my advice with a grain of salt and see if it makes sense. Maybe a more experienced person will pipe up and better lead you in the right direction. Good luck.

 

[Stickboy]

i think Stone's troubleshooting is right on track, I 2nd his method.....
-mike

 

[Greg_B]

Short note:

It has been -6 to -9C the last few mornings on the wet coast (ya ya...I know -30 to -40 other places). Yesterday I did not use my override push button, wanting to see if the factory timer is working. It is. Yesterday morning it was on for 6-7sec before clicking off. Truck coughed a little and the pedal had to be held down a little per usual, however it started.

The manual cycle is great, in that you can cycle it longer if you want. Nice to know the factory system is working, so I can use it as a datum for how long to use the manual system at different temperatures.

gb

 

[Stone]

One thing I've also noticed is that if the factory settings feel it's cold enough to warrant a certain amount of glow, let's say 5 seconds, and you manually override the system by pushing in the button, when you let go of the button the system will still do its normal 5 second cycle. Mike, Greg...is this how it works in your system too? I know Greg's should do this as I wired it exactly the same way as mine...

 

[Greg_B]

That I had not noticed Stone, but then I was not paying attention till yesterday when I started playing. Will check over the next few days and let you know.

EDIT-Same thing here. Released the override button, and the system still glowed for about 5 seconds, then I heard the relay click off and the voltage guage moved up.END EDIT

gb

 

[Stickboy]

very funny you mention that stone, i just noticed that same thing yesterday.... timer went for 4 seconds. shut it off to add a little more time and after i let off after about 2 seconds it finished it's 4 second glow. started up first turn with a little bit of pedal.... 8 deg f outside....

mike

 

[Stone]

Cool...I like that feature actually! So the net effect is like adding more time to the glow timer when the timer feels it's cold enough to warrant a glow start. Cheers.

 

[crushers]

i have been using Stony's setup for a while now and i have now installed it on all the LJ71s that have come in. i am also offering this to anyone that wants it on all the new trucks that come in...
you hit 1000 on this one Stoney...
cheers

 

[Stone]

Aahh...thanks, Wayne...but I can't take full credit for it. Mike figured it out and opened the possibilities. Definitely one of the worthwhile mods to do on a diesel. Cheers.

 

[crushers]

ooops, me bad. thanks goes to both you and Stickboy...
cheers