Newbie Instrument Cluster question
 

I searched the best I could to avoid multi posting but no luck so here it goes....I have an 88 Mustang GT VERT....the owner before me threw a 140MPH speedo cluster in but I can tell from looking at it that it is not for an 88....(I think the years of those speedos that i researched are 87-89...then 90-93 with the addition of an airbag). Anywho, my oil pressure and gas guages do not work. I already changed out both sending units for each with no luck. Is there in fact a malfunction of this between the design of the two different "models"? Another symptom would be that when I turn my right turn signal on, the tach back light blinks rather than the green arrow (stop laughing)...just want to ask before i pull the trigger and "downgrade" my speedo.

Sorry to hear about your troubles.

Well, it could be a few things. It could be a broken line on the printed circuit board on the back of your cluster (they're quite fragile). OR it could be your cluster's voltage regulator has gone bad (that's the little circuit board that plugs into the back of the cluster, it's bolted or screwed on on earlier clusters without airbags and I don't know if the earlier ones are removable). Or it could be a series of shorts in the respective wires from the components to the dash. If I were to bet money, I'd bet its the printed circuit board because of the blinker issue. That's the only thing that comes to mind that would cause blinker arrows and gauges to fail. Only thing I can suggest to diagnose the problem is to pull the cluster and check to see if there are any breaks in the circuits. If there are, you know what to do my friend.

Also, did you check for power going to the sending units your having troubles with?

Thanks Doomstein, I will take a look at it.

dreamer1uk, yes, both units are getting power

No problem, if you find some breaks in the printed board and decide you want to keep the cluster there are several options for repairs. You can grab whats called a circuit writer pen at radioshack, usually for under 20 bucks, which uses a silver based conductive ink to fix breaks in those types of circuits. you just color in the gap and 'bing', problem solved. There's also new conductive glues out there that do the same thing.

Just throwing that out there.

Well first off you need to figure out if you have the correct cluster. Using a 87-89 in a 90-93 will cause a few issues and vice versa. The wiring on the plugs are a little different because of the airbags. Get a pic of the cluster that you have.

That's a very good point.

While uncommon, I have seen people jam 89 clusters into 90-93 model foxes and vice-versa. If your car is an 89, and its cluster is arched at the bottom instead of flat straight across, the guy you bought the car from is lazy and should be beaten with an oar.

I did it when I first got the 93 running because I already had a 87 cluster. This caused a no charging issue. The sensing wire for the volts gauge is the same wiring that sends the 12v signal to the alternator to allow it to charge. This wire has different locations on each of the 2 cluster styles.

Thanks for everybody here that helped and gave advise. It turned out that there is indeed a difference between the 87-89 and 90-93 clusters. After hours of troubleshooting and knuckle busting, I got a nice 88 cluster from Ebay. All systems are good to go. I'm going to try and sell the 90-93 and reain some mulah...off to my next project...the headers! :-)