[ron2424]

I hope someone can point me in the right direction. I have a choptop '50 ford running 12 volt (GM drivetrain). I have a set of VDO gauges. I am running a power inverter to run a large 5.1 surround sound system. When the inverter is crankin, my temp guage reads real high at high idle. When I get back to idle it settles to normal. Also at night when I have the lights on, it does the same thing. When I get back to idle it settles. It also settles when I shut off the lights. I have bolstered all the grounds. The ammeter is reading at around 13-13.5, and drops to 12.5 when the inverter is pulling hard or when I have the lights on. VDO suggested it was a ground issue, but what kind of problem?. Is the inverter drawing to much current from the altenator? Electrical is NOT my forte, so any suggestions would be GREATLY appreciated. Thanks in advance...Ron

[Chevl_Steve]

Hmmmm my first thought was that it may not be electrical at all....at least not directly. I am not sure ...just a guess. When you demand a lot out of your alternator, it puts a pretty good load on the engine. If you are at or near idle and don't have an optimum cooling system you MAY be overstressing the cooling system?

If it's a ground problem, which it could be, make sure you have a good ground going from battery to engine, then from engine to body, and from body to guages. The connections must be clean and tight.

Also, are you sure your alternator is keeping up with the demands of the inverter? What's your alternator output max rating?

Steve

[TooMany2count]

Originally posted by ron2424
. The ammeter is reading at around 13-13.5, and drops to 12.5 when the inverter is pulling hard or when I have the lights on. VDO suggested it was a ground issue, but what kind of problem?. Is the inverter drawing to much current from the altenator? Electrical is NOT my forte, so any suggestions would be GREATLY appreciated. Thanks in advance...Ron

first, I believe you have a "VOLT" meter & not an "AMP" meter w/the readings you're giving us, & I'll have to agree w/Steve you most likely need a 125+ amp alt (like an Alt for an ambulance) for your set up if its pulling that kinda voltage. Because not only are you powering your inverter but the rest of the car. When the voltage drops to around 12volts thats barely enough to run the car & the accessories you may have on while trying to keep the battery charged........joe

[ron2424]

Thank you gentleman. I will check the continuity of the grounds throughout the system. I'm assuming a higher capacity alternator would be available through Summit? It is a Voltmeter...my mistake. I don't notice any performance difference when it's pulling hard.

P.S. When I shut down the current drawing units i.e. lights or inverter, the gauge comes back to normal almost immediately. I have installed a 4 core rad and it never runs over 190, 200 in the So cal summer heat....

finally...summit has a Gm 140 amp alternator...any input or concerns for running such an alternator with everything else being "stock"??