Help Fitting aftermarket Rev Counter / Boost gauge

[mortcars]

Here's hoping someone can help..

I'm trying to fit an aftermarket rev counter and boost gauge to my 1997 1.9td T4

couple of issues ive got...

first the boost gauge - at first the needle wobbeled soo much i couldnt get a reading now ive added in a T-Piece its steady just not moving much above Zero???

then the rev counter, ive run a wire to the alternator hoping to find the W connection there but there are only 3 connections and none marked W. so any ideas where else i can pick that sense up from?

Ta

Dan

[undernutter]

Couldnt tell you a thing about boost gauges, but, revcounters:

I put an ad-hoc tacho in my pug 205 that I pulled from a scrap mondeo, it was a relatively simple job. Extraordinarily heath-robinson looking, cable tied to the dash top, but it works!

On any revcounter there are three connections: 12v positive (ignition), chasssis ground and signal. As far as I know signal may come from the low tension side of the coil or from the distributor, and has nothing to do with the alternator.

Mine is a pov-spec XL car, but top-of the tree models had revcounters fitted, so there was a wire present blanked off behind the dash which was this signal wire. This originated at the distributor. Have a look in your cars wiring diagram to see if this exists, I'm sure it would on a t4, I can tell you my old mans 1997 example (R plate 2.4 GL derv non-turbo auto) example has one factory fitted in the cluster.

Your 12v ignition feed and chassis ground should be easy to find, any one (within reason) will do, again they may already be there as per the signal wire, but if not the instrumnent cluster itself usually has a positive feed to its PCB which you can tap into.

I put up a thread about this some time ago I'll see if I can find it for you

HTH
Dave

[undernutter]

heres that thread, if it helps.

retrorides.proboards.com/index.cgi?action=display&board=techni&thread=121117&page=1

If you cant get hold of a wiring diagram I'll see if I can get some photo's of my old mans T4 workshop manual for yis.

[cobblers]

Problem being, diesels don't have a distributor hence taking a feed off the alternator - they use the unrectified AC as an RPM signal.

I'd reckon these will have a crank sensor somewhere. If not, I've worked on stacks of 1.9td t4s that do so it's bound to be something you can retro fit.

As for the boost gauge, are you sure you've piped it up to the right hose? Seems like you're behind a one way valve for the brake servo? I'm an idiot, diesels have a vac pump for this

[dude]

undernutter - mortcars car is a diesel, and diesels don't have a coil Most take the signal from the alternator, if they don't have a crank sensor fitted. I do not know if the alt has to have a specific connector on it or not though.
I personally would have tried the 3 different connections until i got a reading

Boost gauges don't like diesels on tick over, as they don't generate any vacuum, so a diesel boost gauge is needed if the wobbling bothers you. a budget solution would be a one-way valve in line with the gauge, as littleturbo wrote in my build thread

But as said, if it does it doesn't stop when you give it some revs you've probably got a leak, connected it wrong, or a defect gauge.

[undernutter]

Derv- no ignition system DOH my bad fellas

As mentioned above crank sensor seems like a good shout, or try each of those connections on the alternator.

I'd still be having a look to see weather or not a signal wire is already in position somewhere behind the dash though: getting wires through the bulkhead has (in my experience) always been such a bore.

[mortcars]

cheers for the replies, ive added cable ties to all the boost pipe connections and i now have a working gauge, just need to get a psi one instead of a bar one and ill try the other 2 alternator connections and see if they work

ta

Dan

[mortcars]

tried all 3 connections on the alternator and nothing, to plan b then ive got to figure out where to get the signal from in the dash or fusebox area

[cobblers]

I'm guessing that your T4 is an earlier one, with the cable driven speedo?

If so, you can replace your clocks with ones out of a passat and get a revcounter that way.

Alternatively, you should have a signal going to the clocks for RPM. It should be the green wire leading to your clocks. You can access it either by getting the clocks out of the dash, or more easily drop the fuse box down (theres a couple of white plastic tabs and it sort of drops down)

The green wire you need is on connector U1, pin 6 (Blue ones, bottom row)



Poke your revcounter wire in the back of that and run the engine up


The T4s use a version of the central electric 2 fusebox, full details are here:
www.a2resource.com/electrical/CE2.html

[mortcars]

Cheers Cobblers, mine should be the non cable driven version so ill get it all apart today and attach the wire and see what happens

[mortcars]

Nope, no luck, i must eb doing somthing wrong, ive tried 2 terminals on the fuseboard, U1-6 like cobblers said and U2-12 i got off the T4 forum. think ill try to buy a full cluster and see if that works.

is there no way i can tap off the alternator even if its not currently there?

[squonk]

Yes, a 'W' terminal can be added by taking a feed from one of the windings. Any competent auto electrician should be able to do it for you.

Here is an example: mk1ultra.com/mods/w_terminal.html

[mortcars]

oh i can do that, cheers mate if the weather picks up ill have a go at that

Dan

[jrevillug]

Are you trying to connect a petrol tacho to the W terminal? If so, it won't work - the signal is just all wrong. At best it won't do anything, at worst it might just damage the tach.

You need a tachometer designed to take the signal from the W terminal.

[mortcars]

Oh its def a diesel one, even says diesel on the front. found a proper set of clocks but the guy wont post so ive emailed him for an address and see where he is.

[jrevillug]

Good work.

Carry on. ;D