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John

John D

Member
Messages
10
Location
Cooperstown, NY
Hello All - 2008 H3 with 106,000. Of late, things have been happening (bad) when I apply the brakes. It started with the headlights dimming when braking and has grown to include the radio dying, the temperature display reading -188, and the speedo dropping to "0". All these symptoms rectify themselves in just a second without me doing anything. I've researched it a bit and found causes ranging from a bad connection (?) to normal operation. Has anyone had this situation and had it corrected? Thanks very much - John
 

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FloridaH3

Well-Known Member
Messages
75
Location
Baltimore
Anytime weird electrical stuff happens, best bet is to chase down all grounds (starting nearest to place of impact, i.e your brake wires), and then reassess.
 

JPaul

Well-Known Member
Messages
2,400
Location
Way up north, UT
Also, on the H3 if you are still running the factory battery terminal clamps then those are possibly the culprit. The H3 has electric assisted power brakes, so I could see a loose or dirty connection at the battery causing those types of issues when braking. Could also be a bad battery, but check the clamps first. Many have replaced the clamps with either brass or lead terminals.

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deserth3

Well-Known Member
Messages
1,069
Location
Conroe, TX
If you want to start messing with something. Start with checking your battery connections.
But it would be best too run it down to a parts store like AutoZone and have then check the charging system and battery.
Problem could be bad or week battery, failing alternator. Corroded or bad connection of wiring.
Before you start messing with stuff. Just get it checked. A decent parts store won't charge you anything.

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alrock

El Diablo
Staff member
Messages
10,442
Location
Scottsdale
Like has been said above, it's either connections or a weak battery. My last AGM battery was giving me ABS errors, loud ground pops in the stereo and other issues.

One thing to note on the H3 is that momentary dimming of the headlights when stepping on the brakes is normal. The alternator is not always engaged so that momentary dipping is the time it takes to reengage the alternator and provide charge to the battery. Still, your symptoms are beyond normal. But this may also indicate an alternator issue, though I'd check the battery first.
 

650Hawk

Well-Known Member
Messages
480
Location
SoCal
Two questions:

1. Do you have a sunroof?
1a. Ever had wet carpet on the passenger side?

2. Do you still have the stock battery cable terminals?
 

John D

Member
Messages
10
Location
Cooperstown, NY
Thank you all very much - seems to be a consistent theme of battery cables and checking the system - i was aware of the alternator deal, but not the battery cables. I know what I'm doing this weekend! And I do have the sunroof, but never any leaks and the truck is kept inside.
 

lowtrac

Well-Known Member
Messages
222
Location
Georgia
The alternator is not always engaged so that momentary dipping is the time it takes to reengage the alternator and provide charge to the battery.

This is the first time I’ve heard this. Is there some kind of internal clutch? Interesting.


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JPaul

Well-Known Member
Messages
2,400
Location
Way up north, UT
This is the first time I’ve heard this. Is there some kind of internal clutch? Interesting.


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No clutch, it's whether or not the computer is energizing the rotor winding's, and I believe it will even regulate how much the rotor winding's are energized to control the output current. Alternators work by generating a magnetic field in the rotor by passing electricity through the winding's in the rotor. As the rotor turns that magnetic field then generates AC electricity in the stator winding's which is then rectified into DC to go to the battery. There are no magnets in an alternator. Google "How do alternators work" and either read about it or watch a Youtube video, it's pretty neat if you're interested in that at all.
 

John D

Member
Messages
10
Location
Cooperstown, NY
Update - I changed the negative battery cable terminal at the battery ( I couldn't do the positive because the cable is too short) and the situation appears to have rectified itself. Could it have been that easy?!
 

JPaul

Well-Known Member
Messages
2,400
Location
Way up north, UT
Update - I changed the negative battery cable terminal at the battery ( I couldn't do the positive because the cable is too short) and the situation appears to have rectified itself. Could it have been that easy?!
I left the factor crimp portion of the terminal on mine and just cut off the clamp portion and then knocked out the little stud and enlarged the hole it leaves and then bolt that to whatever terminal you choose. Works just fine. I'll eventually put something else on the cable ends but for now I've had zero issues.

8c94a8bcf480a6deb0c588cdb828a445.jpg


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