ENG/MET wire for HUD

[Reride]

I completed installing a digital UB3 into my '92 CSC (with a lot of help from RobertlSaar) I only need info on which wire on the HUD harness to connect the Eng/mer wire and if I can connect BRN check gauges from '92 harness to the SES wire to make it work? MANY THANKS TO ROBERTlSAAR !!!!!!!for his assistance. Steve.

[RobertISaar]

what are you trying to do with the check guages/SES wires? almost sounds like you're trying to trigger the SES light based off of the check guages indicator? maybe i'm reading it wrong.

 

http://i.imgur.com/7AJsSla.png

 

that answer your question about the english/metric switch?

[Reride]

I'm want to trigger the check gauges light in the HUD from the SES light on the digi dash. Since my'92 CS had a BRN wire in D2 for the Check gauges light in the HUD and the digi dash uses a SES light, not a Check gauges light. I hope this makes sense.

[RobertISaar]

okay, makes sense. i don't see any reason why it wouldn't work, since both the cluster and HUD would supply the positive side of the circuit while the ECM would switch the negative side when necessary.

 

from the disassembling of the HUD i have(THINK it's a 94 model year unit), yours should have the check guages indicator enabled. earlier years had a low fuel indicator, but no check guages indicator, while the later stuff had check guages, but no low fuel. oddly enough, the GP had both. since i'm using a CS HUD in a GP, i opened it up and investigated to see how easy it would be to enable the low fuel indicator on a later unit. turns out all it needed was a single wire soldered in.

[Reride]

Thanks again RobertlSaar!!! If I understand what you are saying about The GP HUD then you should be able to remove the PC board from a GP and transplant into a CS HUD and run a wire to low fuel gauge in dash. Correct?

[RobertISaar]

while you could do that, it would be cheaper and faster just to solder in a single wire on the CD HUD control board. or at least it was for me. keep in mind this is also with a GP cluster, which output both signals on the normal connector.

 

that's assuming you have a low fuel indicator in the cluster to begin with. certain clusters just lit up the check guages indicator instead of a low fuel light.

[Reride]

There is a low fuel light next the fuel guage on the '89 digi, but I don't know how it gets signal. I can make it light up in the HUD by supplying pin E with power from the PPL wire for the fuel guage but just stays on. Do you know where it would get its signal from?

[RobertISaar]

if i had a digi UB3 cluster in front of me, it would probably take 2 minutes to trace out how it's operated, but if i had to guess, i'd say that there is a RC circuit that feeds a filtered and smoothed fuel level signal to a comparitor on the board. when the signal matches or drops below another voltage signal, the low fuel lamp kicks on. is the low fuel indicator part of the vacuum florescent display or is it an incandescent bulb? if it's a bulb and it always has positive voltage fed to it and it's ground switched to turn on/off, then you could connect one wire and make it all work as a signal for the HUD to turn on it's low fuel indicator.

 

GM tended to do this with its clusters, but not always.

[Reride]

It's part of the vacuum display. It's the word LOW next to fuel gauge, it lights up during the bulb test so I know it has connectivity to something. P.S. sorry for the late response but the internet service in my area has been down this afternoon.

[RobertISaar]

that's a potentially tricky thing then.... it is probably a circuit that gets switched ground to activate/deactivate, if it is, easy mod. if not, it's probably still doable, but vacuum florescent likes it some voltage... i think somewhere along the lines of 20-30 volts? would have to work around that to have it control the HUD indicator.

[Reride]

Do you have any ideas on how I could make this happen?

[RobertISaar]

got a good digital camera and multimeter?

[Reride]

Camera ,yes. Mulitmeter needs battery.

[RobertISaar]

well, take pics of what you can, i'll see if i can do some preliminary guessing.

[Reride]

I got lucky.. found a AAA battery in the junk drawer. What do you want me to take pics of?

[RobertISaar]

anything and everything important. the vacuum florescent display around the low fuel and fuel level indicator would be good. i ASSUME you'll see a large capacitor on the board, probably near 470uF knowing GM, that would be for the fuel level filtering, otherwise, the circuit for the fuel level sender need to be traced starting at the connector and seeing where they end up.

[Reride]

middle rearOK. I will take some pics of display and post. It will take a few mintues to take the digi UB3 apart.

Edited May 8, 2013 by Reride

[Reride]

How are these?

Edited May 8, 2013 by Reride

[Reride]

The rear pics aren't representative of display. There are two PC boards stacked up.

Edited May 8, 2013 by Reride

[RobertISaar]

well, GM certainly went in a different direction compared to other clusters of the era...

 

i imagine you see quite a few pins coming off of the vacuum display? well, one way or another, we need to determine which one controls the low fuel light. the "easiest" way is to brute-force check the voltage on every pin with the cluster powered up since the lit-up segments are going to receive a healthy positive voltage to light them up.

 

http://www.tubeclockdb.com/vfd-tubes/100-simple-vfd-tester.html

 

that's a decent example of what can be expected to be seen here. the "grid" section used by the low fuel indicator is shared with the fuel level guage, so it will be receiving power at all times. the filaments will also need to be active in that area as well, but obviously at a fairly low voltage. the "element" pins are what is going to make it all work. essentially, you'll need to power up the cluster and start checking suspect pins while varying the fuel level signal above and below the threshold needed to light up the indicator, you'll probably 2 or 3 pins total that change from none to high voltage while doing this, since i assume the low indicator will go on and off when the fuel level transitions between the red and non-red zones. at that point, you'll just have to determine which pin(s) controls the fuel level segments and which one controls the indicator. this could be done via trial and error considering the low pin-count at that point.

[Reride]

Correct Me if I'm wrong, but no matter what I do to make the low fuel light come on, the check gauges light will come on to. Unless I can separate the signal from the check gauges light source. If this is the case then I might as well run a wire from terminal E on the HUD to the check gauges wire on the cluster connector to give the low fuel light in the HUD power. Also do know what plugs into the 5 pin plug at the rear lower center of cluster?

[RobertISaar]

it's a possibility, but i don't have a cluster to examine to see what all would happen under various scenarios.

 

and no idea on the connector. if i had to guess, i'd say it's possibly for communications(reprogramming the odometer, for instance).

[Reride]

I'm thinking that if one cannot separate the signal it would activate both low fuel and check engine light. So until I can find a second digital UB3 to play with ( I don't want to take the chance of screwing this one up ) I will splice into the check gauges wire and have the same thing. Getting back to eng/met wire in the HUD do you know where the B11 switch is on the '92 car? Mine has no obvious switch accept in the '89 digital dash.

[RobertISaar]

from what i understand, the cluster switches not only itself, but also the HUD into metric mode?

[94 olds vert]

When I switch my Digi UB3 to metric the HUD also does. I'm drawing a blank on what extra wire I had to hook up if I even had to. I do recall something about an extra wire.