skipc
NAXJA Forum User
- Location
- Georgia & points west and south
As asked, here is an update on fixing the declining gauges of the 89 XJ.
I took the cluster out and inspected the wiring. I cleaned the contacts of the connectors (didnt' really need it) and checked signal levels. The supply was close to battery voltage without loads. I also checked the voltages at the fuse block since almost all of the car supply goes through the key switch - quite a bottleneck. About 0.25v is lost there.
However, the resistance from ground on the cluster to frame ground was 15 ohms! To make the story short, the worst batt ground connection was from the block to the firewall. No cleaning would really improve things, yet there's no rust or such on it. I ran a 10ga wire from the battery to that firewall ground bolt. It resulted in 2 whole volts improvement at the lighter, higher oil pressure readings (20psi hot vs 10psi), and the voltmeter about a volt low instead of 2-3 volts.
The blower motor really takes it down though, so I'm going to probably bring in 4 or 6 ga lines from the battery and feed from that instead of relying on old wiring that's probably marginally rated. The key switch has about 3 or 4 main lines (circuits) it switches to supply the fuse block. I think I'll use those lines to drive relays that will switch in power from these 4ga connections instead. That should get me the extra volt on the gauge and maybe even true oil pressure.
Other benefits from wiring a ground directly to body include better starting - shorter cranking (about a sec less) and when it hits, it's on; faster window motors, and the elec locks seem more reliable - the hatch started working again.
The fuel gauge was always pretty accurate, as seems the temp. Perhaps the sensor levels or design make them less affected.
If I find more I'll write.
I took the cluster out and inspected the wiring. I cleaned the contacts of the connectors (didnt' really need it) and checked signal levels. The supply was close to battery voltage without loads. I also checked the voltages at the fuse block since almost all of the car supply goes through the key switch - quite a bottleneck. About 0.25v is lost there.
However, the resistance from ground on the cluster to frame ground was 15 ohms! To make the story short, the worst batt ground connection was from the block to the firewall. No cleaning would really improve things, yet there's no rust or such on it. I ran a 10ga wire from the battery to that firewall ground bolt. It resulted in 2 whole volts improvement at the lighter, higher oil pressure readings (20psi hot vs 10psi), and the voltmeter about a volt low instead of 2-3 volts.
The blower motor really takes it down though, so I'm going to probably bring in 4 or 6 ga lines from the battery and feed from that instead of relying on old wiring that's probably marginally rated. The key switch has about 3 or 4 main lines (circuits) it switches to supply the fuse block. I think I'll use those lines to drive relays that will switch in power from these 4ga connections instead. That should get me the extra volt on the gauge and maybe even true oil pressure.
Other benefits from wiring a ground directly to body include better starting - shorter cranking (about a sec less) and when it hits, it's on; faster window motors, and the elec locks seem more reliable - the hatch started working again.
The fuel gauge was always pretty accurate, as seems the temp. Perhaps the sensor levels or design make them less affected.
If I find more I'll write.