Weird Problem

[Sailorlou]

Hi All,

Hope someone can help me diagnose the problem I'm having with my 1994 5.8L Bronco XLT.

Recently I started having a problem with the ABS braking system. The brakes would sometimes pull to the left especially when turning left and then the ABS light would come on and then the ABS light would go off. I figured that was probably a speed sensor problem and I decided to unplug the main fuse for the ABS until I had time to order the new parts. This stopped the pulling to the left issue. Then something strange started to happen. Intermittently my temperature gauge and oil pressure gauge would start reading higher then normal and at the same time my voltage gauge would read lower then normal. If I would cause a load on the system, such as turning on the lights or hitting the brakes the gauges would sometimes return to their normal readings. This is on-going. Sometimes just turning off the engine and restarting will clear the gauge issue and then it might recur when a load is applied.
So what do you think? Do I have a voltage regulator or computer problem?

 

[Tiha]

Interesting.

Well not a computer problem. Could be an alternator problem. Kind of sounds more like a ground issue.

You can certainly remove the alternator and have it tested for free at most parts stores. Might be the easiest place to start.

 

[Sailorlou]

Thanks for your response Tiha.
Would an alternator problem cause the temp and oil pressure gauges to read higher then normal? Also, I recently drove back from Mexico to Washington State and even though this problem occurred for the whole trip my battery seemed to hold a full charge. The Temp gauge would read near hot but when I stopped and checked the engine temp was normal. The oil pressure gauge would read near the top end of the scale as well. The volt gauge would only drop a little bit below the normal center. These would all occur simultaneously and then they would sometimes just return to normal. I tried putting the ABS fuse back in, but it made no difference, it would just cause the brakes to pull to the left again.

 

[Tiha]

ABS is completely unrelated.

The gauges work off of resistance and voltage. It is designed to work within certain ranges.
Like a fuel gauge is 0-93 ohms or something like that.

Once one of those specs go off it throws the accuracy off. So if you are over voltage, like alternator over charging. Everything would seem normal, could make the gauges read incorrectly, but still keep the battery charged properly. But Eventually it will destroy the battery from over charging.

Resistance also increases with bad wires, or loose and corroded wire connections. So if you have a ground wire that is loose or dirty it could cause the false readings.
Loose connections get hot. As heat goes up so does resistance. That resistance adds additional ohms to the circuit causing it to operate outside its calibrated ohm range.

Since it is more than one gauge doing this to you, then it is something common like the ground wire for the entire cluster.

So it is kind of hard to troubleshoot from here. Could be an over voltage situation, or could be a loose, corroded wire situation.

 

[Sailorlou]

Sounds reasonable, but if it was an over voltage problem why would the voltage gauge read lower then normal?
I'll do some voltage checks and check all the wiring connections.

 

[Tiha]

right, it may bot be an over voltage problem at all. Just trying to throw everything out there that I can think of that could fit your scenario. I am sure other guys will have some ideas as well.

 

[L\Bronco]

Hi All,

Hope someone can help me diagnose the problem I'm having with my 1994 5.8L Bronco XLT.

Recently I started having a problem with the ABS braking system. The brakes would sometimes pull to the left especially when turning left and then the ABS light would come on and then the ABS light would go off. I figured that was probably a speed sensor problem and I decided to unplug the main fuse for the ABS until I had time to order the new parts. This stopped the pulling to the left issue. Then something strange started to happen. Intermittently my temperature gauge and oil pressure gauge would start reading higher then normal and at the same time my voltage gauge would read lower then normal. If I would cause a load on the system, such as turning on the lights or hitting the brakes the gauges would sometimes return to their normal readings. This is on-going. Sometimes just turning off the engine and restarting will clear the gauge issue and then it might recur when a load is applied.
So what do you think? Do I have a voltage regulator or computer problem?

Hey Sailorlou:
The instrument cluster mainly uses ground G-100 and G-200
4Wheel ABS uses G-100
G100 is on the Rad support behind the washer\coolant bottle
G200 is behind the passenger kick panel.
You may have a ground issue. I'd check both of these as well as the main ground on the engine block and especially the body grounds. (should be one off of the back of the intake area to the firewall or possibly tied off of the main ground near the battery.
Hope that helps
Cheers!

 

[Sailorlou]

Hey Sailorlou:
The instrument cluster mainly uses ground G-100 and G-200
4Wheel ABS uses G-100
G100 is on the Rad support behind the washer\coolant bottle
G200 is behind the passenger kick panel.
You may have a ground issue. I'd check both of these as well as the main ground on the engine block and especially the body grounds. (should be one off of the back of the intake area to the firewall or possibly tied off of the main ground near the battery.
Hope that helps
Cheers!

Thanks for the info, I'll check that out.

 

[Motech]

On you ABS issue...
I get it's currently "bypassed" by disabling the ABS entirely. Just reminded me of a couple diagnosis of similar symptoms I've done in the past that turned out to be mismatched wheel speed sensor reluctors--tooth count IIRC--on recently replaced brake discs.

 

[L\Bronco]

On you ABS issue...
I get it's currently "bypassed" by disabling the ABS entirely. Just reminded me of a couple diagnosis of similar symptoms I've done in the past that turned out to be mismatched wheel speed sensor reluctors--tooth count IIRC--on recently replaced brake discs.

That's a really good point, I have also seen loose reluctors cause a similar issue.