electronic pryo wont work when hardwired into 40

[shorty_f0rty]

Hi guys,

well i bought a cheap pyro off a mate for $100 and he bought it off ebay for $100 but upon wiring it up the other night i discovered that it doesnt actually measure anything..

its completely electric, no capilaries or anything, my mechanic installed the sender about 1foot from the manifold (down were the extracts converge)..

there is nothing reading when gassing it up hills..

anyway.. as I don't really have much to loose since its already busted, I was wondering if there is anything I can do to :
1) check the sender
2) check the guage itself
3) ensure its all working as it should inside?

I know its a long shot but i dont have much other choice. as its all electronic, is there any risk of kinking the sender cable as per a mechanical temp guage? theres just 2 wires that come out from the sender...

any thoughts on how I can try and make the best of this situation is appreciated.

Thanks,

ANdrew

p.s. here is a pic of the cheapy gauge incase you see them for sale on ebay:

[mickyd555]

the probe needs to be wired correctly, if you have it arse about then it wont read anything.

Try swapping the wires from the probe around before you say its stuffed.

[shorty_f0rty]

i say its stuffed cos the wires are already crimped for the probe and can only go one way...
i will swap them around and see if that works though..

i was thinking more along the lines of how to test the resistance on the sender or however they work to send the signal to the guage..

oh and I had followed the destructions that came with it as to what the uncrimped wires do.. sorry i forgot to mention that..

[Toy80Diesel]

checkout this page on EGT readings. It tells you how to test the probe using a normal multimeter. I've done this before and even though I couldn't get the same readings, the readings did change with a few revs of the engine so I knew the probe wasn't stuffed.

http://autospeed.drive.com.au/cms/article.html?&A=0371

[shorty_f0rty]

checkout this page on EGT readings. It tells you how to test the probe using a normal multimeter. I've done this before and even though I couldn't get the same readings, the readings did change with a few revs of the engine so I knew the probe wasn't stuffed.

http://autospeed.drive.com.au/cms/article.html?&A=0371

great.. this is exactly the type of thing i was after.. thanks for the link!

[shorty_f0rty]

well.. i confirmed teh sender is working.. so thats a start..

[shorty_f0rty]

the guage also works..

when i installed the guage the other night i didnt see the "requires 12v negative ground" sticker..

using a 12v UPS battery i tested it and what do you know? it works!

"problem exists between guage and installer"

thanks for the help anyway guys..

[KiwiBacon]

checkout this page on EGT readings. It tells you how to test the probe using a normal multimeter. I've done this before and even though I couldn't get the same readings, the readings did change with a few revs of the engine so I knew the probe wasn't stuffed.

http://autospeed.drive.com.au/cms/article.html?&A=0371

I used a cigarette lighter to heat the probe when I installed mine. I initially thought mine was stuffed, but it was just a bigger probe with a slower response time.

[shorty_f0rty]

i can't seem to get the gauge to work from 12v from teh car..

I'm still using a 12v UPS battery for it at the moment..

attempted running a ground from the negative of both batteries with no luck. the guage just wouldn't give a reading.

when i run it off the ups battery it reads the EGT's ok.. but not off the car 12v.. i wonder if it needs a relay?

[KiwiBacon]

i can't seem to get the gauge to work from 12v from teh car..

I'm still using a 12v UPS battery for it at the moment..

attempted running a ground from the negative of both batteries with no luck. the guage just wouldn't give a reading.

when i run it off the ups battery it reads the EGT's ok.. but not off the car 12v.. i wonder if it needs a relay?

Does the 12v car supply check out with a multimeter?

[shorty_f0rty]

i can't seem to get the gauge to work from 12v from teh car..

I'm still using a 12v UPS battery for it at the moment..

attempted running a ground from the negative of both batteries with no luck. the guage just wouldn't give a reading.

when i run it off the ups battery it reads the EGT's ok.. but not off the car 12v.. i wonder if it needs a relay?

Does the 12v car supply check out with a multimeter?

yep it reads 12v and the guage lights up as if its got power. just doesnt give a reading
this is when i was grounding to the body or grounding to the negative terminal on the battery..

has me stuffed!

[j-top paj]

thats odd

[Toy80Diesel]

Just wondering, is you gauge in a metal case? maybe that needs an earth?

[shorty_f0rty]

Just wondering, is you gauge in a metal case? maybe that needs an earth?

Nope.. the entire guage is plastic..

I am taking 12v off the fuseblock which is switched power (so it only comes on for ACC's, otherwise it would drain the battery if it was on all the time)..

[Toy80Diesel]

I am taking 12v off the fuseblock which is switched power (so it only comes on for ACC's, otherwise it would drain the battery if it was on all the time)..

Well it must have earth because it lights up. I would be suspecting the 12v running from acc's must be faulty. It should work off your vehicle battery just as it is from your other battery. It will end up being something simple that was overlooked...

[shorty_f0rty]

well.. i had another go at hard wiring the pyro up this weekend (had removed the UPS battery for a while and wouldn't mind a working pyro again).. I though I had it wired up to the ACC , more specifically the radio fuse which still got a little current for the radio memory.

When I wired it up this time i took the +ve from the ON circuit. I can confirm the guage works but again when its hard wired it wont receive a reading.

I wonder if its because the battery -ve terminal is grounded to the body? the Pyro works fine when its connected directly to the +ve and -ve terminals of a non-grounded UPS battery (12v7ah). The -ve grnd wire is connected directly to the -ve terminal of the battery..

anyone else have any other ideas?

[GeneralFubashi]

one of the wires from the probe is grounded to the body?

Its the same as cheap multimeters. They use an internal battery which they compare the voltage to be measured against. If you try hooking up a multimeter and use the car battery as its power source, and then try measuring the car battery voltage, its not going to work as it has a common ground.

I have no idea how the pyro works, but could well be the same way, and would explain what you have described.
Sam

[shorty_f0rty]

When i start in the morning and "glow" the voltage drops to around 10.9v.. when it does this the pyro peaks at around 1300c and then slowly drops,

when I start the 40 and its running normally with the voltage over 12v the pyro stays at 0c and doesnt move.

[-Scott-]

Very weird.

The next time you hook up the battery to test the gauge connect the -ve of the battery to the chassis of the car.

I think the General is close to the answer. I have a theory.

My guess is that one side of the probe is connected to the car chassis, but the other input in the gauge is connected to the negative supply. When the gauge supply is isolated from the chassis, it works - connect the two and it stuffs up. During glow plug use, there's a voltage drop between the block/manifold and the chassis (created by the glow plug current) which the gauge is interpreting as the thermocouple voltage.

Have you removed the probe from the exhaust & tested the gauge that way?

Edit: must not post when sober...

[shorty_f0rty]

Have you removed the probe from the exhaust & tested the gauge that way?

no.. I haven't yet but thats a good idea.

The probe is taped into the extractors, the extractors are connected to the block which is grounded to the chassis. The -ve is also grounded to the chassis so the probe and the -ve ground are both grounding to the same thing.

When using a standalone battery the probe is still grounded to the chassis but not the same -ve as the power..