Some gauges not working

My fuel gauge doesn't work and the low fuel light is on. Also, neither the oil press or water temp gauges work. I swapped out my gauge cluster with a known good one from the old '87 today and those 3 gauges still don't work (although the amp gauge does) and the low fuel light is still on.

I did some searching here and the common problem in most of the threads seems to be the ignition switch. Could that be the culprit for 3 of the 4 gauges not working?

Possibly, the power to the gages comes from the ignition switch RUN position terminal A1.

Replace the switch.

Before replacing the switch, check for voltage at the cluster end of the 8 ohm resistance wire. I forget the terminal # in the cluster connector, but it is a GY/Y wire kind of hanging loose. Using a DMM with key in run, you should have batt voltage at that wire. If no voltage, and the wire is intact (rare cases of them burning out), replace the ig sw.

you can pull the cover off the column and visually check to see if the switch is seperating. if it is try to squeeze the switch and see if the guages respond. if they do replace the switch. just a quick check.

The one thing that everyone missed, except JeffK, is the GY/Y wire. The problem is is that there are two of those wires that goes into the plug. One large and one small, and they both go the the black plug on the back side of the ignition switch. If the black plug is melted in the middle then you have found your culprit. if the little wire is broken, then the gauges will not work, this is the wire that gives the gauges 12V. I had to repair the little one on my nephews car when I got it up and going, and this is how I found out. Just make sure that the little wire has not burned in two. It is hard to soldier so I just took a crimp connector and fixed it that way. Works like a charm.

Jim B .

Well, I checked the voltage at the GY/Y wire and it's got batt voltage. There's a BLK wire that runs to the same terminal. If there's 12v going to the terminal, than there's voltage coming in. Like I said, my amp gauge works. Maybe I just have a bad fuel sending unit, oil pressure s/u and water temp s/u (isn't the wt s/u on the drivers side of the block, down low?) The car does have 193,000 on it!

You guys are gonna love this! I just discovered I have a cooling problem also! Took it for a ride and after about 20 min I noticed a ton of smoke coming from the tailpipe. Don't think it was white but a really light blue. Kinda smelled like oil. Motor made that clacking sound like when you overheat. Got it home and it was HOT! Definitely overheated. Guess I'm gonna be swapping a head gasket too! Hope the head's not cracked too bad! One thing though, it only smokes in gear, not in neutral.

This is actually fun! Got the ABS working good. Brakes are a little spongy. Pulled the front wheels and it looks like the original rotors are almost worn completely through! New pads though! I'm finding all kinds of neat new stuff!! Good thing I've got a couple of other cars for transportation!

If GY/Y has batt voltage, I would suspect a bad IVR.

Amp gauge is not powered via the IVR or GY/Y power feed wire, so it will work with the other gauges dead.

As a last check of the GY/Y wire circuit, be sure it can supply current by using a SMALL test light, like a #194 bulb between the GY/Y wire and ground. The bulb wont glow full brightness due to the 8 ohm resitantce of the wire. If that checks out, likely problem is a dead IVR.

Jeff, that makes sense except for the gauge cluster that I just swapped in worked when I pulled it out of the '87. It's been awhile since I drove that '87 but I do remember the wt gauge slowly climbing 'cause of the cracked head. Not sure about the fuel gauge but I remember the oil press was registering. So that would eliminate the IVR, wouldn't it?

Originally posted by evintho:
Jeff, that makes sense except for the gauge cluster that I just swapped in worked when I pulled it out of the '87. It's been awhile since I drove that '87 but I do remember the wt gauge slowly climbing 'cause of the cracked head. Not sure about the fuel gauge but I remember the oil press was registering. So that would eliminate the IVR, wouldn't it?

You would think so, but who knows..... One way to check to see if the IVR is working at all is to install the cluster electrical plugs. Then go in the trunk and tap into the fuel sender wires under the carpet (push pins thru the wires) with a DMM set on Volts (an analog volt meter actually works better for this, but few people have them around anymore). Turn key to RUN. The voltage at the sender should cycle up and down with a frequency of once every second or 2. How much it cycles up/down depends on the fill in the tank.

Can also bench test the IVR and gauges by hooking a 12 V batt to the correcct pins on the cluster connector, and using a resistor from gauge terminals to ground. 10ohm = gauge pegged at max, 22 ohm = gauge at half, 73 ohm = gauge at lowest mark.

Last, be sure the cluster connector and plastic PC flex board on the cluster are clean and making contact. I have had problems with these in the past, and have used 1500 grit to clean everything up and restore operation of various cluster functions.