I've had my SHO for about a month and only drove it about 15 miles from my house to my buddy's shop where I changed the MTX, clutch, etc and noticed nothing out of the ordinary. I've since got everything back together and have put roughly 100-150 miles on it and have noticed the driving, interior, and gauge lights pulsing as I drive. I also can hear the fuel pump pulsing also. I put a new battery in last week and had the alternator tested, and it tested good but I'm still leaning towards the alternator. Anyone else had the problem by chance?
SHO lights flickering/pulsing
- Thread starter Sham73187
- Start date
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its not likely the alternator because usually when the alternator is bad, by the time you notice it the battery is so dead the car won't start.
I think from your description you have a bad ground. One of the grounds is not making a good connection - likely from not being tightened properly when you put it all back together.
I think from your description you have a bad ground. One of the grounds is not making a good connection - likely from not being tightened properly when you put it all back together.
93markVIII
SHO Member
also thinking alternator.
Storm-Chaser
New Member
While a ground wire is possible, there is only one ground wire that has to be removed to change the an MTX - the ground wire to one of the front bellhousing bolts. Unless you removed the upper intake, the only other one I can think of is the grounding strap from the upper plenum to the firewall.
Two alternator malfunctions can cause flickering lights.
The most common is a faulty voltage regulator. While you had the alternator tested, its possible that the problem becomes noticeable when the electrical system is under a load.
A less common alternator problem is a bad diode. These control the flow of electricity from the alternator, that has the effect of producing DC power from the alternator's AC output. Think of them as a kind of one-way valve that only lets the electricity flow in one direction (DC current).
When a diode fails, it allows reverse current flow in one of the three phases of the alternator output. The end result is that you have stable current flow through 240° of the 360° of each turn of the alternator, but at some point there is a minor reverse current flow during the 60° of the 120° of the bad diode's circuit.
That temporary reverse current flow is what produces the temporary dimming of the lights and lighted displays, that you notice as flickering. It is most noticeable at low rpm, and indistinguishable at high rpm.
If the alternator was tested on the vehicle, most of the simple testers don't tell you if one or more diodes have failed within the alternators rectifier bridge.
If the flickering is tied to rpm, take the alternator off and have it tested on a machine that checks the diodes.
Two alternator malfunctions can cause flickering lights.
The most common is a faulty voltage regulator. While you had the alternator tested, its possible that the problem becomes noticeable when the electrical system is under a load.
A less common alternator problem is a bad diode. These control the flow of electricity from the alternator, that has the effect of producing DC power from the alternator's AC output. Think of them as a kind of one-way valve that only lets the electricity flow in one direction (DC current).
When a diode fails, it allows reverse current flow in one of the three phases of the alternator output. The end result is that you have stable current flow through 240° of the 360° of each turn of the alternator, but at some point there is a minor reverse current flow during the 60° of the 120° of the bad diode's circuit.
That temporary reverse current flow is what produces the temporary dimming of the lights and lighted displays, that you notice as flickering. It is most noticeable at low rpm, and indistinguishable at high rpm.
If the alternator was tested on the vehicle, most of the simple testers don't tell you if one or more diodes have failed within the alternators rectifier bridge.
If the flickering is tied to rpm, take the alternator off and have it tested on a machine that checks the diodes.
I ordered a new alternator that should be in today, if the problem continues after I change it I'll put it back on the lift and check and see if I missed anything. Last night I did notice at low rpm the lights didn't pulsate as much as the did at higher rpm. I'll probably take the old one off and have if checked like you said to be sure.
Storm-Chaser
New Member
Find out anything ???
