Tach guts

[Dan Himan]

Tach has not worked, opened and found the following.



Anybody know part #s for these?

[Guest765]

Originally Posted by Dan Himan

Tach has not worked, opened and found the following.


Anybody know part #s for these?

the spots you circled appear to be fine. the spots i have noted with red arrows and circles appear to be broken or eroded traces on your PCB which could be repaired with a steady hand and a soldering iron plus a few carefully trimmed pieces of aluminum foil. i've done this type of repair on older motherboard PCB's which physically BLEW apart traces from improper voltage including copious scorching. full restoration of functionality was obtained. maybe you can take a closer look at those spots and good luck.

EDIT; after looking more closely at your first picture its pretty obvious you have an overvoltage related problem, especially looking at the bluing caused by high temperature. i would NOT install a new tach until you have located the reason for the overvoltage.

[Dan Himan]

Those spots are glue from the other side. I did find the short.

[Guest765]

Originally Posted by Dan Himan

Those spots are glue from the other side. I did find the short.

where was your short, if your don't mind me asking?

also, you will have to order a whole new tach. pelican probably carries them, shop around for a price and use your best judgment when making any purchase.

good luck

[HondaDustR]

Looks like resistors that could be replaced if you were able to figure out what values they are. Who knows what else is damaged, though. You might be able to test the parts on a good tach with a multimeter and then try to fix that one as a spare, unless someone else will test or read off the markings on those for you.

[Guest765]

Resistor Color Code Table And Calculator

no idea if radio shack still sells single parts like resistors. no harm in trying to repair it, test the resistors with a multimeter against the intended value before attempting replacement.

[Dan Himan]

Something with the HG plug near the DME. I will start another post about that. I replaced the resistors, I used a 100ohms, I cant see the colors due to them being burnt.

[HondaDustR]

they're not going to measure right either since they're burnt. Radio shack still stocks most common parts like resistors, but they are overpriced...oh wait, so is everything else in there.

[Dan Himan]

The worker was as helpful as a sack of bricks.

[Guest765]

Originally Posted by Dan Himan

The worker was as helpful as a sack of bricks.

you can't just "replace with 100ohms", you know that, right?




right?

[Dan Himan]

Yea, i know.

[andyshoun]

Dan,
I have a tach I pulled pulled from a junk car. It is untested. I don't need it (I used the speedo). It came from a '86 manual transmission.
Andy

[Dan Himan]

I looks like they changes a little from 86 to 87, not sure if it would work.

[Guest765]

Originally Posted by Dan Himan

I looks like they changes a little from 86 to 87, not sure if it would work.

the reference signal it is interpreting is the same, should work with no issues.

[Dan Himan]

Are you saying the tach runs on the cranksenso/speed sensor, not the Hall sender, or maybe the Hall sender signal is the same as the crank sensor/speed sensor.

[Guest765]

Originally Posted by Dan Himan

Are you saying the tach runs on the cranksenso/speed sensor, not the Hall sender, or maybe the Hall sender signal is the same as the crank sensor/speed sensor.

my understanding is that the hall sensor is only for ignition timing, and the flywheel/crank speed sensor is for the tach, as the method to test the crank speed sensor is to watch the tach for a "bounce" as you crank the engine without starting.

[porsche4life]

Radioshack still sells resistors, if your local store is decent...


What year cluster is that from... I've got a few I'd sell you the tach out of....

[Dan Himan]

The tach is for the 1987 944S, radioshack here didn't have crap. If i read the resistors correctly, it would be a 1/4 watt 100ohm 1%, and a 1 watt 6.2 ohms, 2%.
I guess any 944 1987-1991 tach will work.

[desertt5]

Originally Posted by Dan Himan

The tach is for the 1987 944S, radioshack here didn't have crap. If i read the resistors correctly, it would be a 1/4 watt 100ohm 1%, and a 1 watt 6.2 ohms, 2%.
I guess any 944 1987-1991 tach will work.

Did you remove at least one leg of the resistor to read it? If not you re shooting in the dark. Your meter will read the circuit, not just thru the one resistor. As already stated, if they are burnt, you wil not know what they "should" read, even if removed from the circuit.

If you want, I have an 87 944S I am parting with a good tach.

[Stephen03]

Bad Beer Rots Our Young Guts But Violence Goes Well... Thats how I remembered the order of the colours on resistors.... untill the test was over haha.