Simple tach question

[robh]

I just installed a procomp 25/8 tach in the a-pillar. The idle seems to be okay but the rpms runs slow after that. When the factory tach reads 3000 the autometer reades 2200. WTF? I used the same green spade connector behind the alt. Could this be a problem? Slow connection? I also used the same power wire to all my gauges. I was wondering if it's possible to have to many gauges on one power source and not allowing the tach to function properly. Any thoughts? TIA

 

[Mr URL]

No, that tach wire connection behind the alternator isn't slow. My Sun tach works fine and is fast. Is this tach DIS compatible?

 

[robh]

Is this tach DIS compatible?

I have no idea. I thought that was only a VDO problem. Maybe it's not getting enough juice?

 

[Mr URL]

Originally posted by robh
Is this tach DIS compatible?

I have no idea. I thought that was only a VDO problem. Maybe it's not getting enough juice?

Distributorless Ignition System. Check your instruction manual. Should say in there if it is compatible. Is the cylinders setup correctly to 6?

 

[BLACK6PACK]

The factory tach is useless. The last 2 cars I rode in with factory tachs (I have a digital dash) were way off. We were cruising through a parking lot and the factory tach was at 4500 rpm!! The aftermarket was around 1500 rpm.

 

[tangofox]

The factory tach I junk. Mine is off about the same as yours. When I had the emissions test done, the machine matched my aftermarket one amost identical.

Strangely, my boost gauge is dead on.

 

[pwhite]

I have a vdo 21/8 tach and have yet to get it to work. When I key up the power it comes up to 0 and will not move. I bought it from postons and they said they had never heard of anybody needing anything programed. called vdo and they said they didnt act like they knew what i was talking about. what is the deal with vdo tachs and what can i do to fix mine. my factory tach reads 5000 all the time but my scan master reads fine Thanks

 

[FJM568]

The VDO tach's need the 5 volt square wave mod done to them for them to work on our cars...VDO USED to do this mod for free, but I've heard they don't any more...

Call up John Spina @ Casper's Electronics...They have an plug-in adapter that goes between the gauge and the tach signal wire to correct the signal so that it would work...

Here's a description from their website...

102007 VDO Tach Signal
Converter Module

This in-line converter is
designed to accept the CCCI
tach signal from the GM
module, and amplify it to allow
proper operation of VDO and
other aftermarket tachometers.
Three wires in, three wires out.
The output of the unit plugs
into the tach, and the input
wires are for +12v, -12v and
TACH signal (white wire) from
the CCCI module.
$30.00

And the link... http://www.casperselectronics.com/cgi-local/store/commerce.cgi?product=INST
It's like the third or fourth item from the bottom of the page...

 

[robh]

aaahhh!!

Is the cylinders setup correctly to 6?

I forgot all about that. I don't even know if there is an adjustment. I will have to check. BTW I wasn't checking it with stock tach but with the scanmaster. So I have a good idea where it should be at. Thanks for the idea.

 

[BLACK6PACK]

On the monster tachs there is a wire on the back of the tach that needs to be clipped in order to work on a 6 cylinder car.

 

[robh]

Thanks guys! I forgot to clip a brown wire on the back. All that torque I forgot I only have a V6