Can anyone give details on what is required to replace the plain gauge cluster (speedometer, temp, gas) for the full gauge cluster with tachometer in a 1989 Bonneville LE?

I want to do the same swap on my '87 Olds delta 88. I have been told it isn't a straightforward old out new in swap, the wiring harness is different apart from anything else.
If this isn't the case I am happy to be wrong.
My main problem is getting hold of the correct cluster and getting it back to the UK.

Roger.

I also want to do this swap, I did it on 95 Ford Taurus but the plugs were the same and it was a simple plug and play swap.

I'll check out the plugs in the junkyard the next time I'm there but that'll be a while since its winter here now.

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1989 Oldsmobile 88 Royale Brougham Regency - Grey on Grey - FE3 - X06 Package - Limo Tint - Clarion HU - 2K Pontiac Grand Am 15" Alloy Rims

If it's like the LeSabre was, which it should be unless the H-body changed radically in '88, the following should apply:

The wire harness from the cluster to each of the sensors is split up into three (main) parts: The cluster harness, the (massive, almost every single wire in the car passes through this harness at some point) dash harness, and the engine harness. The (main) connectors are in the middle of the dashboard and at the firewall pass-through. The piece in the middle (dash harness) should be common to each trim level/option. The engine harness and cluster harness are specific to the options ordered.

Cluster harness:
The pinout for the cluster connector varies; and any wires you may be missing at the cluster harness should be present in the main connector in the middle of the dashboard, you would have to pull the dash out to get to it though, and need to be added to the harness between the cluster and the main dash connector. Also any wires that are pinned differently between the clusters would need to be swapped. Other options are to splice a new wire into the correct spot on the firewall passthrough or ECM connector and run it to the cluster directly. Or, if the junkyard has one, pull the correct cluster harness.

Engine harness:
Out in the engine bay the oil pressure sender will be different for a gauge, the ICM has the tach wire extra and the coolant sensor will have an extra wire for the gauge. The harness in the engine bay is matched to the cluster, as well as the two sensors are completely different. For example, without the oil pressure gauge all you have is a pressure switch that illuminates a dummy light; with the oil pressure guage you actually have an oil pressure sending unit that has a variable resistance based on the actual pressure in the oil passages. Connecting an oil pressure gauge to a pressure switch will make the oil pressure gauge peg and probably never work again. Also the connector is different on the sender (at least mine was). The sender has a third pin for the gauge, because the fuel pump circuit still used the oil pressure switch. My '86 had two wires on one pin for the switch. One wire was for the fuel pump circuit and the other went to the gauge cluster. When I installed the sender, I had to use a DMM to figure which wire went to the gauge cluster (they were the same color) and connected it to the 3rd pin on the sender. Again, the point here is you either have to add wires (and components) to the harness at the wire pass-through, run a direct wire, or pull the correct harness.

I strongly recommend getting the chassis service manual for these swaps, they list all the pinouts, wiring schematics, etc. And I wouldn't be surprised to see that they didn't wire up the two H-bodys the same way.

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Boost addict


The Fleet:
'93 SSEi - Twincharged + manual Build thread
'97 Camaro - Top swap
'05 STS - V8, AWD, her DD
'92 Trofeo - Fair weather DD
'99 Montana - top swap 3800
'04 Sierra 2500HD - LLY Duramax

Current project:
Something cool, trust me.

Upcoming projects:
'92 Bonneville SSE
'87 LeSabre T-type
'67 LeSabre

Gone to greener pastures:
'84 Sierra Classic - Twin turbo 3800
'97 LeSabre - Top swap

RIP:
'86 LeSabre - pictures
'93 SE - L67

I have the full cluster here:
for-sale-or-trade/topic30803.html

Let me know I can take a pick of the plug. I remember it to be one vertical pin connector
in the back, plus a connector for the compass.

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90 SSE Bonneville Sold but not forgotten.