Voltage drop and wastegate issue

Hi

Long time reader, first time post.
First up thanks for all the info over the year's. I have fixed a lot of issues from the posts here.

I have a July 94 Suburban imported new and converted to right hand drive in 94 by a factory approved converter.

I am having an electrical issue that I cannot find an answer to here. I have searched the forum extensively ... I think.

I have cleaned and tested all grounds earth straps and live straps. I have replaced the batteries. I have tested and had an auto sparky test the alternator and it is fine. I have cleaned and tested the lead from the alternator.

Problem 1.
At the batteries I am getting 14v. At the firewall junction I am getting 13.9 or there abouts volts.
On the dash and scantech tool I am getting about12v on start and for the first 20-30 minutes of driving. Then it drops to around 10v.
I am not getting a charge light or ses light on the dash.
Clearly I have a resistance issue or an ecm issue somewhere? Ideas would be good.

Problem 2.
I have a new vacuum pump and lines and a new wastegate solenoid. I have a boost gauge on the dash. Turbo boosts fine for first 20-30 minutes of driving then drops to zero and stays there. When at zero the wastegate arm can be moved easily so the solenoid must be getting a message to kill the vacuum. Some times if I drop the throttle to idle and try again the turbo will boost again for a while. Eventually I get an ses light and plenty of black smoke and no boost.
Turbo will boost fine no matter the voltage but I guess they must be related.
If I shut down and restart the turbo still will not boost. If I shut down and let everything cool off completely then good to go for another 20-30 minutes. So perhaps heat related.
Intake temp sensor reads ok according to ranges posted in threads here.
This one is very frustrating and makes the truck unusable.

I have had this vehicle almost 10 years. Voltage issue and turbo issue are recent.

Over my ownership I have replaced due to failure the following, PMD, FSS, ECM.

I have done a lot of other testing, but all ideas gladly received.

Thanks.
Ron

Hi

My first suggestion would be a faulty ignition switch.

These area a sliding type (linear) switch and the contacts wear out and resistances goes way up.

Check the ign switch and get the voltage thing handled and then go after the boost issue.

It is not uncommon to see the plugs at the ign switch melted due to the resistance issues

Good luck

Hi

Thanks for the tip.
Had a quick look and read up ... is there a special tool needed to get to the ignition switch or just I am not holding-my-mouth-right? Seems not as straight forward as I might have expected.
Thanks
Ron

The switch is mounted on top of the steering column.

DISCONNECT BATTERIES

No need to do anything with the unit you put the key into.

Remove the plastic valance under the dash area and drop the column down until the steering wheel is nearly touching the front seat.

The switch is on the top side of the column.

A long rod from the lock mechanism connects to the switch.

The plugs from the wiring harness plug into the switch assembly.

Remove the plugs and then undo the fasteners holding the switch the the column.


Give the plugs and their contacts a good looking over for signs of excess heat due to high amp draw ( Can happen due to switch failure)

If plugs are in good order... Replace the switch, plugs and such and reassemble the column.

Note *******

Before you reinstall the column be sure the key activates the switch properly and smoothly..

Good luck

GM changed the location of the ignition switch,but i am not sure what year.
My 97 3500 had it on the top of the column behind/around the tumbler.Under the plastic cover for the signal switch,ignition switch.The screws that hold it together are underneath.Everyone that i have has had someone else in there and have busted the plastic by not finding all the screws.
Google or YouTube it and you should find a video that someone has posted to watch befor you tackle it.