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I have an 85 Camaro SC, I've been wanting to clean up the gauge cluster and replace all the missing gauges and do away with the after market ones I have hanging from the dash pad. My tach and oil pressure gauges are gone and the temp gauge doesn't work due to it not being hooked up. I plan on replacing the speedo with a 145mph speedo and finding another tach/oil gauge but I'm not sure if it will work due the fact that the ECM isnt hooked at all to my knowledge. So my questions are:
1. What does the temp harness/plug and sender look like and where are they located?
2. What does the original tach wire and plug look like and where isn't located?
3. Where does the oil pressure sender harness come from the main harness and what does it look like?
4. Will any of these work as the ECM is un used by the engine completely?
94 TBI 350 Block and heads, Edelbrock 1406 carb and RPM Airgap intake, pertronix HEI Ignition.
Well, I'd start by doing a search and looking at old threads on the subject. It's been done before, and most likely someone already has asked and answered the questions you're asking. Not to discourage you, but you can find an old answer alot faster than waiting for someone to post a new one.
Pretty sure the oil LIGHT switch and coolant temp LIGHT switch utilize the same wiring that would be used with the oil pressure sender and coolant temp gauge sender. So really you'd just need to change the switches out for senders, and change the lights over to gauges. I can't say on the tach, but I would imagine if the tach terminal on the distributor doesn't have anything plugged into it, you could get the correct GM terminal/connector assembly and wire it in. Find a C100 diagram for your year make model car and look for the tach signal wire, check both sides of the connector at the firewall, I'd imagine one or both sides is probably already wired for it. If not again, it's just a matter of getting the terminal and adding it to the connector block.
That said, I don't know, back when I worried about such things, I didn't have the skill to do it, and now I don't have to worry about it because all my projects are later thirdgens. I've done similar wiring projects, and they're really pretty simple, but it helps to find someone who's done what you want to do and see how they did it.
I've tried a search but I just keep coming up with everything except anything to do with gauges. I'm sure someone has done this, it's just a matter of sifting through the forum.
Use Google. Type in words like "idiot lights" swap gauges cluster change etc add site:thirdgen.org to the end of the search terms, and it'll show results from here.
I'll be honest, I'm not sure it's a sport coupe, it has all needle gauges except the tach/oil and the volts work perfectly so I'm not sure this was an idiot light car. I know it had a 2.6 at one time but all the rpo codes are gone.
This is the cluster I have except it's an 85 speedo and the tach is missing, fuel and volts work perfectly. Could it be an RS? This car has been molested a lot before I got it.
Okay so I think I've found what I needed, my only question now is v8 cluster plug compatible with a v6 plug socket? (All the circuitry the same in the pins?) That's the only thing I havent managed to find.
1. What does the temp harness/plug and sender look like and where are they located? 2. What does the original tach wire and plug look like and where isn't located? 3. Where does the oil pressure sender harness come from the main harness and what does it look like? 4. Will any of these work as the ECM is un used by the engine completely?
1-2-3: All 3 of these wires comes from the C100 connector passing thru the firewall on the drivers side of the engine bay. Tach wire connects to the distributor TACH terminal, Oil Pressure sending unit is normally mounted on a brass fitting at the back of the engine rear "China Wall", & the TEMP sending unit should be installed in the front coolant port of the drivers side head. Here is the wiring schematic for a 1985 Camaro C100 connector: You will find the TACH, OIL, and TEMP, & VOLT wires there.
4: All of these gauges will work perfectly fine without an ECM connected. Search for & buy GAUGE SENDING UNITS ( TEMP, OIL ) for a 1985 V8 Camaro.
**** Be sure that you use an 82-85 GAUGES Cluster housing/printed circuit to be sure that all wiring remains compatible. The BRAKE warning light was moved from one side of the cluster to the other side of the cluster starting in 86. ( 1986 cluster wiring changed a little; individual gauges will swap from cluster to cluster, but installing a 'complete' 86 + gauges cluster in an 85 or earlier Camaro with gauges will "screw" with a couple circuits. )
1-2-3: All 3 of these wires comes from the C100 connector passing thru the firewall on the drivers side of the engine bay. Tach wire connects to the distributor TACH terminal, Oil Pressure sending unit is normally mounted on a brass fitting at the back of the engine rear "China Wall", & the TEMP sending unit should be installed in the front coolant port of the drivers side head. Here is the wiring schematic for a 1985 Camaro C100 connector: You will find the TACH, OIL, and TEMP, & VOLT wires there.
4: All of these gauges will work perfectly fine without an ECM connected. Search for & buy GAUGE SENDING UNITS ( TEMP, OIL ) for a 1985 V8 Camaro.
**** Be sure that you use an 82-85 GAUGES Cluster housing/printed circuit to be sure that all wiring remains compatible. The BRAKE warning light was moved from one side of the cluster to the other side of the cluster starting in 86. ( 1986 cluster wiring changed a little; individual gauges will swap from cluster to cluster, but installing a 'complete' 86 + gauges cluster in an 85 or earlier Camaro with gauges will "screw" with a couple circuits. )
So this is what I dug out of the very faded vin, it was a fuel injected 2.8 liter, lb4 sport coupe.
Also, do these look familiar? They were taped and tucked away under the break booster...
Yep, looks like a oil pressure switch and or sensor. Fuel injected cars, early fuel injected cars have one switch/sender for the gauge, and another for the fuel pump circuit.
Yep, looks like a oil pressure switch and or sensor. Fuel injected cars, early fuel injected cars have one switch/sender for the gauge, and another for the fuel pump circuit.
Awesome, now I just have to find the tach wire and the temp sender wire!
The round one in that last pic is for the A/C switch in the high pressure line. The square one in the top of #15 is either the cold start injector switch plug, or a fuel injector plug. If it was a MPFI 2.8, it should have had a divorced coil distributor, so the tach wire would go to the coil instead of the distributor.
Jump on The Google and search for GM HEI Tach Wire and you should see a lot of options for the stock style plugs for power and tach that will plug right into your cap/coil
Image stolen from Ebay for example. Then just find the White wire at position D5 on the C100, and splice it to the connector.
The GM remote (divorced) coil would have had a plug like this... The white wire on the gray connector is the one you'd connect to the distributor cap/coil, but the gray connector probably got chopped if they spliced the old distributor power to the new distributor.
Yea, I didn't even think about it having a separate coil, that completely makes since. So basically if I splice into or completely cut the white wire from where ever it's going in the harness (to the rear engine abyss) and run it straight to the TACH terminal on my HEI, the stock tach should work right?
Okay, update. The wire for the tach pin is black/white, anyone know what that's about? I traced it a good ways through the harness and it hits a conectorcand then disappears back into the harness, havent finished tracing it yet...85 sc, originally a mpfi 2.8l and it looks as if the coolant sending unit wire isnt even pinned. I got my new cluster in and compared the printed circuit to the old one and they are the same but some of the wires in the bulk head diagram do not match my car or are completely missing altogether. I also found light blue, green, green and white and I think brown wires cut in the harness on the passenger side of the brake booster. This is getting rough smh
Okay, so after some digging I did manage to find out that the tach wire on a v6 can be black and white from the pinout D6 on the bulkhead. So thank God on that. Now I just have to figure out why there is no wiring for the coolant temp and what those wire that were cut go to. I've noticed the wiring for my washer pump is missing also but according to my Haynes manual, the wiring for it should come from the wiper motor I'm not seeing anything except for the wiring for the wiper motor itself. Did some models not come with a washer pump or something? My signal lever has to wash function on it...
Last edited by 85RS; 05-24-2019 at 07:58 AM.
Reason: Double post
There is no wiring for the washer pump DIRECTLY. The wiring plug that connects to the wiper assembly is all you need,..... the pump is controlled by the wiper assembly.
Hmmm what year were they separated from the wiper motor. The one I ordered from tgr is the one where the pump is on the reservoir itself. If the wiring doesn't exist on the car, where should I tap into to make it work?
This is the wiper motor as is. All visible outlets are plugged in, although I do not see a place for a pump or the hoses so I'm assuming it had a pump separate and most likely on the reservoir (which was missing when I bought the car). Again it is a VIN S 85 sport coupe originally equipped with a MPFI 2.8L.
This is the connector at the bottom of the motor (yellow and red or pink wires)
The pump in its entirety.
Theres a weird ridge above where my fingers are but no outlet or hoses/ connections)
weather pack that connects to LH side of motor, wires are grey, yellow, green, ?purple?
Bring it back and get the correct wiper pump for your car..... ??
The pumps were mounted in the tank from 88-92.
Ordered it from thirdgen ranch, I'm not even sure it's the incorrect pump or not seeing as the wiper motor isnt equipped with a pump and the wiring is still up in the air.
The washer pump gets installed directly into the wiper assembly cover. Why make things complicated ?? Just buy the correct pump, install it in your Wiper Motor Cover, connect the hoses and plugs ------> done.
I didnt even realize that the pump was inside the cover. I get to work on this thing like maybe twice a month so it's hard to even keep track of what I'm doing.
So to update, I've traced all the wires for the cluster and sending units, just got to buy the units themselves but I went to test out the tach and it was pegged at 7k, when I unplugged it it stayed pegged for a second and then began to slowly fall but stopped around 2500rpm. Any insight as to what's going on? I've read on a bunch posts about similar problems but nothing quite like this.
First guess,..... Bad Tachometer ( very common ). If you can get your hands on a dwell meter you can connect it to the tachometer wire at the distributor to find out what the true readings are.
04-22-2019, 07:07 PM
I didnt even realize that the pump was inside the cover. I get to work on this thing like maybe twice a month so it's hard to even keep track of what I'm doing. 
I do it all the time,... looking so close at sumthin' that you can't/don't see what your looking for ------> till you back-up a bit !! 
