Police Auxiliary Gauge Wiring Question

[1987 GMC Jimmy]

I'd just like to make sure I've got all this right. I'm getting close to wiring up my 9C1 auxiliary cluster in my Caprice, and I wanted to make sure I was correct with the way the wiring works. The Voltmeter can be wired to one of the "IGN" spots on the fuse panel (+), and it needs to be grounded (-). The Oil Pressure gauge needs to be wired to a canister style sending unit (+) and grounded. The Coolant Temperature gauge needs to be wired to the sender (+) and grounded (-). Just to verify, the sender that I need for the later, 1980's GM gauges is the one with the little ball on the end, not the spade style dummy light sender. Finally, for the two backlights, I need to wire them into the headlights and ground. I have a silly little ashtray light that I could use instead of wiring to the switch. Could I wire two No. 168 bulbs to that one wire, or will that blow the fuse? I just feel like that would be easier than going straight to the headlight switch. And can any of this stuff be teed like the ground wires and again the backlight wires, or does everything need to be independent? I'm actually pretty good at working with the factory harness and repairing it as needed whether it be through connectors or soldering, but I've never added anything before so I wanted to make sure the map in my head was correct before I undertook this without a diagram or a harness.

 

[CorvairGeek]

I'd just like to make sure I've got all this right. I'm getting close to wiring up my 9C1 auxiliary cluster in my Caprice, and I wanted to make sure I was correct with the way the wiring works. The Voltmeter can be wired to one of the "IGN" spots on the fuse panel (+), and it needs to be grounded (-). The Oil Pressure gauge needs to be wired to a canister style sending unit (+) and grounded. The Coolant Temperature gauge needs to be wired to the sender (+) and grounded (-). Just to verify, the sender that I need for the later, 1980's GM gauges is the one with the little ball on the end, not the spade style dummy light sender. Finally, for the two backlights, I need to wire them into the headlights and ground. I have a silly little ashtray light that I could use instead of wiring to the switch. Could I wire two No. 168 bulbs to that one wire, or will that blow the fuse? I just feel like that would be easier than going straight to the headlight switch. And can any of this stuff be teed like the ground wires and again the backlight wires, or does everything need to be independent? I'm actually pretty good at working with the factory harness and repairing it as needed whether it be through connectors or soldering, but I've never added anything before so I wanted to make sure the map in my head was correct before I undertook this without a diagram or a harness.

That sounds correct.
IIRC, some of the GM terminal ends (if you have the 9C1 harness) were designed for both the 'spade' style connector and a little cut out to slip over the 'button' style sending unit, so the same harness can be used with or without gauges. I do have a spade style connector on the sending unit in my car (gauges, not 9C1). I don't know if the 9C1 sending unit was unique or if it was standard GM.

You will be fine with multiple 168/194 bulbs from the ash tray light. Their current is very low.

Were you going to leave the temp or oil idiot lights in place? I always wanted to have the temp gauge sending unit in one head and the temp idiot light in the other.

Pre '85 had extra, unused terminal on the light switch that were handy for my stereo / keyless entry project, but I've never worked with the newer switch. I would guess that it would, as the switch was universal and Twilight Sentinel was offered which required extra connections. If it is difficult to get out as the older switch, it may not be worth it either.

Do you have the entire 9C1 cluster like this '89?

You must be registered for see images attach

 

[Camar068]

hmmm....do they make other gauges that could go in that spot? You could possibly fit those into the vent above the temperature controls in our trucks. Be nice to have Fuel pressure, oil temp and trans temp if it would work.

Research time lol. thanks for the post.

 

[1987 GMC Jimmy]

That sounds correct.
IIRC, some of the GM terminal ends (if you have the 9C1 harness) were designed for both the 'spade' style connector and a little cut out to slip over the 'button' style sending unit, so the same harness can be used with or without gauges. I do have a spade style connector on the sending unit in my car (gauges, not 9C1). I don't know if the 9C1 sending unit was unique or if it was standard GM.

You will be fine with multiple 168/194 bulbs from the ash tray light. Their current is very low.

Were you going to leave the temp or oil idiot lights in place? I always wanted to have the temp gauge sending unit in one head and the temp idiot light in the other.

Pre '85 had extra, unused terminal on the light switch that were handy for my stereo / keyless entry project, but I've never worked with the newer switch. I would guess that it would, as the switch was universal and Twilight Sentinel was offered which required extra connections. If it is difficult to get out as the older switch, it may not be worth it either.

Do you have the entire 9C1 cluster like this '89?

You must be registered for see images attach

As far as the auxiliary cluster goes, I have the female plugs and a little bit of the wiring coming out from them and I have the wires that go to the oil pressure and coolant temp senders in their original, dummy light form. I don't have the full harness for them so I'll just have to splice some stuff in the middle. I am aware that the female connector for the temp sender can work with the spade and the button. I'm just not sure which one to use. In the square bodies, people have had issues of getting the wrong temp sending unit and the temperature readout being somewhat inaccurate. I don't know if the Caprice gauges are different. I'm pretty certain that I'm going to need the canister shaped oil pressure sender, but I'm just gonna wing it with the spade style temp sender and switch it out if the readout is more innaccurste than it normally would be. Same dilemma in my Jimmy. It runs at a nice 196 give or take a little, but the gauge reads about 235 with the spade style sender. I pulled the bulbs from the temp and oil dummy lights so I was just planning on depending on the gauge. I agree it would be cool, but I just didn't think of that. I haven't had good luck with them either. My heater core was totally trashed this summer, and it was boiling out the overflow as I pulled in my driveway, but the light never came on. Mine's an '86 model with a sticker date of 11/85, but I'm not sure on the headlight switch. It does have some '85 components (i.e. two neck instead of three neck fuel sender), and I'm sure I haven't found all of them yet. It doesn't have twilight sentinel, but I wish it did. My dad's '89 Caprice Classic Brougham LS has it, and I've always liked that. I do have the big 9C1 cluster, but I'm sorry to say I broke the speedo needle shaft (not the needle) so I'm kind of at a loss with it. The odometer in mine is really sloppy, too. I wanted to rebuild it with my good cluster, but it was a different needle and shaft so I was worried the calibration would be completely out of whack. I'm still debating on whether to send it to Jackson, MS to a reputable professional or get another one and try again later. I'd like to have a 9C1 thing going on with it when I eventually get done. The instrumentation for sure but also some stiffer shocks, an A-pillar spotlight, some nice dog dish style hubcaps, and a more powerful 305 (or 350 for when I get tired of the 305).

 

[1987 GMC Jimmy]

hmmm....do they make other gauges that could go in that spot? You could possibly fit those into the vent above the temperature controls in our trucks. Be nice to have Fuel pressure, oil temp and trans temp if it would work.

Research time lol. thanks for the post.

I see what you're saying. That would be cool. For the 9C1 auxiliary cluster, that's all they have, but you may be able to get an aftermarket gauge cluster like that or get your own small gauges and make a panel out of ABS plastic or something.

 

[bucket]

I pulled one of those little gauge clusters years ago, I think I got the whole harness too. I'm thinking they plugged into the fuse panel somewhere for power. Would need to look at it again to be sure.