got a 2.5 n/a swap, but gauges dont work...

[narenji]

I just got a 2.5 n/a swap into my 91 legacy l wagon. the car runs really well, but my shop had some issues with the gauges. the motor is from a 99 rs, so the ecu requires a vss to operate properly. the shop said that this caused him to not be able to hook up the speedometer/odometer. it also doesnt have a working tach, or temp gauge. what works is the fuel gauge, and all the indicators/lights. he said that my best bet would be to get some autometer gauges and make them work in the cluster. are there any other options i can look into? are clusters from turbo cars different?

thanks in advance,
-naren.

[vrg3]

What do you mean by "2.5 N/A swap?"

You're using the engine from the RS? And the ECU? What about the transmission?

the ecu requires a vss to operate properly.

So does your stock ECU. Stock, your car had a speedometer cable going from the transmission to the gauge cluster, and a VSS built into the gauge cluster. A wire runs from that into the ECU.

The RS had a sensor threaded into the transmission right where the cable went on your stock setup. A wire went from this sensor to the gauge cluster and the ECU.

If you switched to an RS transmission, I believe the correct solution is to swap your stock speedometer cable over. Then you'll have a functioning speedometer and a VSS signal at the ECU harness.

the shop said that this caused him to not be able to hook up the speedometer/odometer.

How well did this shop know what they were doing?

it also doesnt have a working tach, or temp gauge.

It should, because as far as I know:

The tach is still just a single wire from the ECU to the gauge cluster.

And the temperature gauge is still just a single wire from the sender to the gauge cluster. I think it does share a ground with some of the engine management stuff though.

Did the shop consult the wiring diagrams?

[narenji]

the swap is a 2.5 n/a (RS) motor from a 99 into my 91 legacy L wagon. it's using the 2.5 ecu from the RS, and the stock legacy transmission. he did use a 2.5 harness and wired that in to the ecu.

if the tach is just one wire, i'll let the guy know. he took the job as something that would be relatively easy, but it turned into something more difficult. he's used to doing ej20 and ej257 swaps into much newer cars (like doing wrx/sti swaps into 2.5 rs's). i think he just got frustrated with all the issues that popped up doing this swap.

i would think that he knows enough about the wiring to figure it out if they were all single wires... there's probably more to it, which is why he had issues.

anyone else have any ideas? thanks.

[vrg3]

Ah, if he used the RS harness then I can see how it'd get more confusing.

A little consultation of the FSM wiring diagrams should show what to do, though. For example, for the temperature gauge, it may be easiest to just run a new single wire from the sender (just a 1/4" spade connector there) all the way to the gauge cluster.

And if the speedometer and odometer are not working, I think that means they removed the speedometer cable. I guess they installed the VSS from the RS. Reinstalling the stock cable, and getting the VSS signal from the gauge cluster, should rectify this.

And running a wire from the tach pin of the ECU to the appropriate pin of the gauge cluster might be the way to go too.

[narenji]

i'll give my guy the info you provided. maybe it'll help. how do you know so much about the wiring? what did you do to your car??
-naren

[vrg3]

I haven't done anything especially big. It's just good stuff to know, for situations like these.

[narenji]

vrg, my guy confirmed that yes, everything but the speedo would work, but he didn't want to take the cluster apart for the other things knowing that he'd have to do it again for the speedo. since the car has a RS ecu, the ecu uses the VSS, and sends an electrical signal to the cluster, but since the 91 legacy cluster is mechanical speedo, it wont work. i'm looking into a couple of options- either autometer speedo/odo, or a complete racepak gauge cluster:
http://www.racepak.com/udx.html

a little pricey, but damn sexy.

[vrg3]

You don't "take the cluster apart;" you just need to access its electrical connectors. It's not that hard to pull the cluster so you can reach back there.

Way easier than earning the money for, installing, and wiring aftermarket gauges.

If your guy doesn't want to do it, you should do it yourself. That's my opinion. We can walk you through it.

[narenji]

i understand about wiring the coolant and tach, but the speedo still wouldnt work, because it's used to a vss directly from the trans, now the rs ecu uses the vss, and sends an electrical signal to the cluster, but since the speedo is mechanical, it doesnt work- do i understand it correctly? he suggested an aftermarket speedo alone would do the trick, and he would wire that, and the tach & water temp gauge at the same time...

[vrg3]

No, that's not correct. You can easily satisfy both the stock gauge cluster and the RS ECU.

In the transmission there is a gear that spins at a rate proportional to the output of the front differential.

In a stock 91, this gear meshes with a cable that is threaded into the transmission. This cable -- the speedometer cable -- goes into the back of the gauge cluster, and the mechanical speedometer and odometer run off it.

The vehicle speed sensor is built into the gauge cluster. So, the spinning of the cable drives the speedometer and odometer and also drives the vehicle speed sensor.

A wire goes from the VSS in the cluster down into the ECU. This wire also goes to the cruise control computer and automatic transmission control unit, if the vehicle is so equipped.

Now, in a 99 RS, it's a little different. The VSS threads directly into the transmission. There's no cable. A wire goes from the VSS into the ECU, cruise control computer, automatic transmission control unit, and the gauge cluster. The RS's speedometer and odometer are driven by a digital signal.

With me so far?

So. All you need to do in your car is reinstall the original speedometer cable. Attach both ends -- have it connected to the transmission and to the gauge cluster. Then, connect the RS ECU's VSS wire (pin 35 of the middle connector, I believe) to the wire that originally went to your stock ECU's VSS pin (pin 11 of the 12-pin connector). I believe the wire is green with a black stripe, at least on your stock harness.

[narenji]

so what you're saying is:
before swap:

trans>cluster (mechanical cable), cluster w/ integrated VSS>stock 91 ecu (digital signal)

now:
vss>ecu...

what it should be:
trans>cluster (mech cable), cluster w/ integ VSS> 99 rs ecu(digital signal)- but i just need to connect RS'ecu's Vss input wire to the wire that used to come out of the cluster...

i'm going back to the shop saturday to see what he can do.

[vrg3]

Yes, I think you have it right.

Before swap:

1) Transmission.
2) Threaded into the transmission is a cable.
3) At the other end of the cable is the cluster.
4) Connected by a wire to the cluster is the ECU.

How your guy has it set up now:

1) Transmission.
2) Threaded into the transmission is a speed sender.
3) Connected by a wire to the sender is the ECU.

How it should be:

1) Transmission.
2) Threaded into the transmission is a cable.
3) At the other end of the cable is the cluster.
4) Connected by a wire to the cluster is the ECU.

Note how "Before swap" and "How it should be" are identical. This is really easy! All he had to do was leave the speedometer alone and just connect the ECU's VSS pin to the VSS signal that your car already had.

Assuming the stock wiring harness is still in the car, that wire is easy to find at the stock ECU connectors. If not, then, yes, you do need to get to the wires at the back of the gauge cluster. But even then, it's easy enough to locate the wire using the wiring diagrams. I believe it's the green-with-blue-stripe wire on the connector that's on the right-hand side of the cluster..

[narenji]

ok great. that'll help a lot. he used an RS engine harness, i believe, because there were too many differences between the 91 harnesses and the 99 rs harness. 91's have ignitors, 99s dont etc. i called him with your point by point analysis, and he said "well, hey, if its like you say, it'll only take me 35 minutes to wire it up!" i'm going to see him on saturday to see if he can fix it. if it works, i'll owe you a 12 pack of beer, or gulab jamun or something...

[vrg3]

Mmm... gulab jamun...

Good luck; I'm 99.99% sure my suggestion will work.