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Discussion Starter · #1 ·
So I have a 99 passodeo and I'm having some issues with my tach and speedometer. While driving my gauges (sometimes one, sometimes the other, sometimes both) drop to bottom and come back instantly. There is no loss of power or anything like that when this happens. Sometimes my stereo looses power when this happens but sometimes not. When the problem arises my blinkers blink super fast at idle but resume normal operation when a little throttle is added. When the problem first started it was just the speedometer randomly dropping to bottom and coming back but now it's both! The rain seems to make it worse but it's hard to confirm that thought. Lastly when the car is warmed up before driving it doesn't seem to do it as often. I have no clue where to start so any advice, opinions or knowledge is welcome and thanks in advance.
 

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1999 Isuzu Rodeo LS 4WD
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When I got my '99 Rodeo three years ago I had a faulty speedometer and fuel gauge (still have a faulty fuel gauge). Speedometer and odometer would stop functioning, so I pulled the dash and put in a 'verified working' gauge cluster from ebay. But this doesn't have the same symptoms or issues it seems, so I wouldn't start throwing parts at it.

It seems like you may have an issue potentially with voltage though - If multiple electrical systems are acting up sporadically, I'd start looking at the battery, how old is it, have you verified the charge on it?
It seems partially like your Alternator is working when generating enough power but it may not be at low rpm and should also be checked.

Rain seems to make it worse
Rain or using your wipers? I think the extra load from the wipers could contribute to the lack of electric power.
 

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Since the stereo and gauge cluster both lose power randomly, it might be a grounding issue. Also test your alternator function just to be sure it's good -- the hitting the throttle and the problem going away is indicative of this
 
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Discussion Starter · #5 ·
When I got my '99 Rodeo three years ago I had a faulty speedometer and fuel gauge (still have a faulty fuel gauge). Speedometer and odometer would stop functioning, so I pulled the dash and put in a 'verified working' gauge cluster from ebay. But this doesn't have the same symptoms or issues it seems, so I wouldn't start throwing parts at it.

It seems like you may have an issue potentially with voltage though - If multiple electrical systems are acting up sporadically, I'd start looking at the battery, how old is it, have you verified the charge on it?
It seems partially like your Alternator is working when generating enough power but it may not be at low rpm and should also be checked.


Rain or using your wipers? I think the extra load from the wipers could contribute to the lack of electric power.
The battery is less than a year old. I thought about the alternator too but the only problem that giving throttle at idle fixes is the blinkers being sped up, the tach and speedo will do there thing at low rpm or high rpm there's no difference. Lastly it seems to be the rain, or at least water on the road. If I go through a puddle or something and splash some water it affects it. But I just don't know wtf. I'll check my battery and alternator voltage out and see if that's the problem. And again thanks for the input.
 

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Discussion Starter · #6 ·
Since the stereo and gauge cluster both lose power randomly, it might be a grounding issue. Also test your alternator function just to be sure it's good -- the hitting the throttle and the problem going away is indicative of this
It very well could be a grounding issue. That's a good point I'll have to look around and check some crap out. But I think I might not have explained it as accurate as possible because the blinkers being sped up is the only thing that happens at idle. All the other things happening are at speed. It can be on smooth roads or bumpy roads makes no difference or 1k rpm or 5k rpm. Thanks again for the input and I'll see about tracking down some grounding issues.
 

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Discussion Starter · #7 ·
You have a loose wire connection under the dash somewhere. Perform a shake test to identify its approximate location.
I have pulled the entire dash off and shaked, wiggled, hit, and beaten every inch of wires I can find and can't replicate the problem. The only thing that's consistent is my frustration on not being able to track the problem down. I think the wiring problem could be underneath or something like that so ill have to climb underneath and shake some stuff when i can find someone to sit inside and watch the gauges. Thanks again for the input.
 

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1999 Isuzu Rodeo LS 4WD
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It very well could be a grounding issue. That's a good point I'll have to look around and check some crap out. But I think I might not have explained it as accurate as possible because the blinkers being sped up is the only thing that happens at idle. All the other things happening are at speed. It can be on smooth roads or bumpy roads makes no difference or 1k rpm or 5k rpm. Thanks again for the input and I'll see about tracking down some grounding issues.
While Occam's Razor is usually the best way to think of a problem, (multiple symptoms attributed to 1 problem would tend to be 1 solution) it may be a grounding issue in conjunction with another electrical issue revealing a bad part like the alternator. I'm not sure myself but is there a diagram floating around for where the grounding points in the cabin & firewall are? That would be a good way to check the immediate grounds for your dash.
 

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Discussion Starter · #9 ·
While Occam's Razor is usually the best way to think of a problem, (multiple symptoms attributed to 1 problem would tend to be 1 solution) it may be a grounding issue in conjunction with another electrical issue revealing a bad part like the alternator. I'm not sure myself but is there a diagram floating around for where the grounding points in the cabin & firewall are? That would be a good way to check the immediate grounds for your dash.
I've looked for diagrams but haven't had much luck. I've found a few but there limited. I was able to find the grounding diagram for the engine bay and checked those out today but didn't see much of anything there. Then someone suggested that I check the rear abs ground and it had a bad connection so I fixed that today. I got my fingers crossed that it was the ground causing the problems but I'm not sure yet because as I have mentioned my problem is intermittent and I can't duplicate it at all. But I'll do some more digging to see if I can find the interior grounding diagrams. Also im still trying to find my damn multimeter to test my alternator or get a day off work to run it to autozone or somewhere to get it tested. Thanks for the imput.
 

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Discussion Starter · #10 ·
So I thought I had found the problem. Which was a broken ground wire on my rear abs/speed sensor. It was fine and all the problems disappeared for a few days. Until today when it snowed and on my way home with wet roads my speedo and tach both dropped and came back a couple times. Nothing like before when they would jump around like a crackhead walking over a sewer grate but still had a few jumps (2-3) in my 4-5 mile commute home. I'm going to check all the other abs/speed sensors as well as the main one on the transmission but can anyone think of anything else to check while I'm climbing under there anyways? Again I thank everyone who has responded to my original question and I thank anyone who throws in there 2 cents at this point.
 
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