95 CHEVY 6.5 SUBURBAN

i have a 95 chevy 6.5 turbo diesel its a k2500 4x4 suburban and i seem to be haveing alternator problems and also glow plug relay switch problems my truck when running stays about a constant 11.5 volts i
called arround and was told that it is suppose to run at 14 volts i went and had my alternator replaced and when then new alternator was installed and ran for about 3 min before it just died i swapt the old one back in and here iam today my glow plug relay switch went out i presume because i cant turn the truck over it just clicks and the throttle service light blinks. what could be the problem
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Greetings,
The Service Throttle light could be from a bad throttle position sending unit on the foot pedal or a bad fuel injection pump and/or pump mount driver. This truck has drive-by-wire throttle with entirely electronic connections from the foot pedal to the fuel injection pump. Check your computer for codes. Setting a code 35 and/or 36 in OBD-I computers or a code 1216 in OBD-II motors will tell you if your going to be spending a lot of money or not for a fuel injection pump. Electronics plays a big part with these motors.
Clicking when you try to start could indicate a weak/bad battery (one or both) or a bad starter and/or starter solenoid. Perhaps even a bad ingnition switch, but less likely so. Check your voltage on both batteries individually and not when linked together. A problem with your glow plug relay could also stem from a battery issue, specifically not having enough juice to run the glow plugs.
Good luck - Jonathan

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