HELP! Installing Caspers knock gauge on 87 TR, problems!

["Turbo-T"]

Alright here goes.

I just finished installing a new Caspers gauge on my 87 Turbo T and I am having some problems.

I hooked the ground to the dash board bolt near the e-brake pedal. I hooked the center to a switched 12 volt source on the fuse block.

I then found the only yellow wire with a black stripe running into the ECM, it was connected to the blue plastic plug on the ECM. I tapped into it and ran the last wire, the C wire into it.

Now here's what's happening...

When I turn the key on, the small green light at the bottom will barely flash on for a split second and then it goes out. The 2nd green light will come on and stay on.

As I am cranking the engine the individual LED's will come on...it will go from green into yellow...

Then once the engine fires the very last red will come on and stay on.

I don't suppose this is supposed to work this way is it?

What seems to be the problem here? I am confused.

Thanks!

 

[BRAD_PADGETT]

The B connector circuit on the knock sensor needs to be attached to a switched battery positive wire. This wire is pink/black stripe which must be off during cranking. I found mine by removing the radio. Do you have the instructions for installing the knock gauge? Let us know. Brad

 

["Turbo-T"]

Yes I have instructions, so you're saying you can't just hook the middle positive wire to just any switched 12 volt source? It absolutely HAS to be the pink/black wire?

Thanks.

 

["Turbo-T"]

Perhaps someone can tell me.....is it the blue plug that has the proper yellow/black striped wire? Or is there one off of the grey plug too?

 

[TurboBuRick]

B7 on the 24 pin connector. http://www.fullthrottletech.com/attachment.php?attachmentid=418&d=1168711565

 

["Turbo-T"]

Folks, I'm beginning to wonder if my gauge is defective...?

Rick87GN, thank you for the link. I double checked, and indeed the wire I tapped into was the yellow/black that comes off of the smaller blue connector. (the other was grey in color)

Well I took the gauge out, turned the key in "run" and tried disconnecting the sensing wire....it went from red to green, then I started the engine.

The lights go to the yellow. Hhhmm.....????

Then for the heck of it I took the car down the street and floored the pedal. The lights moved to 1 or 2 yellows over, but then stayed there and did not return to the green.

Then on the way back I floored it again, this time the lights moved from yellow into the red and stayed there.

I believe this is supposed to return to green after 5 seconds of no knock right? Well mine doesn't go back to green unless you shut off the ignition.

So now I'm thinking I have a bad gauge....perhaps someone can verify?

 

[TurboBuRick]

Yep, sounds like a bad gauge to me. Send it back for an exchange.

 

["Turbo-T"]

Thanx, I bought it from Gbodyparts.com....should I send it back to them? Or Caspers?

 

[Junior Samples]

Same deal with mine, I had nothing but probs. Once i took the advice from directions and soldered everything it magically worked

 

["Turbo-T"]

Only thing is I have it soldered and still have problems.

I did notice this though: if I disconnect the sensing wire and leave the other two the lower standby light comes on. But if I touch the sensing wire the lower standby light goes out and the first light comes on.

If I disconnect the sensing wire the light stays on, but if I touch it again the 2nd light will come on.

When the sensing wire is disconnected the 2nd light stays on, but if touched again it goes out and the 3rd light comes on.

This can be repeated until the last light (red) is on, after that if you disconnect the sensing wire the red light stays on but doesn't go back to green...you have to shut off the key to reset it.

Also of interest I did a voltage check at the sensing wire with the key on and engine not running and got a 9 volt DC reading. Not sure if this is normal or not.

 

[Junior Samples]

ya know its exactly what mine was doing, i had even tried a toggle switch, i rig'd up oh like ah crap i cant think of it..like a hood light type release where the pin is up and contact is made..well anyway i rigged that up with the ground and every time i pressed the pin n released...another light would come on in series starting with GGGYYY then RR and stop at last red then i press one more time and hold/release then middle OK green light would come on..pain in the rear man

then one day it just fixed itself after i soldered em so who knows i wish i had a better answer for ya

 

["Turbo-T"]

I thought I'd give all here an update.

I reinstalled the gauge running the 12 volt + wire off of the radio fuse, then I installed a push button switch that breaks the ground.

I found out the gauge doesn't peg out anymore when starting but at the same time the standby LED doesn't stay on, instead it goes immediatley to the first LED.

Plus when i get into the boost the gauge doesn't reset itself after 5 seconds. So I guess I have a bad gauge.

I can however reset it using the little push button. :biggrin: