Hi. I’m traveling in my 1994 Brave with a Chevy P30 base (454 TBI, computer controlled Trans). While driving my dash gauges “froze” (alt meter zero, Speedo 62, temp 220 and oil pressure 40ish, all ok but the alt). Measured 12.4 bolts across battery so assumed alternator. The serpentine belt was ok and water pump working so I continued driving by jumping the coach batteries to the engine battery and running the generator to keep everything charged. While driving the automatic trans stopped shifting (I think it’s in “Limp Mode”). Took it to a Lambs auto and tire shop. They measured 11.5 volts out of the alternator, replaced it with a new one but then still measured 11.5 volts with the new one. They are putting the old alternator back in, not charging me, and sending me away. Two questions: 1) does anyone know a good place to take it for this type of problem in the Round Rock / Austin Tx area, and 2) any idea what might be the problem? Thank you. John
P30 chassis - 1994 Brave Electrical Problem
- Thread starter Cupcake
- Start date
The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.
If you have answers, please help by responding to the unanswered posts.
gwinger
Well-known member
Did they at least load test test the battery?
Gary RV_Wizard
Site Team
Alternator voltage regulation is driven by a system voltage feedback wire to the alternator. Typically a wire from the ignition switch. If that wire gets disconnected or the voltage is skewed high or low, the alternator output will be improper. But I would think (hope?) any tech replacing an alternator would be aware of that and verify it is working properly.
Thanks. I don’t know that they checked the system voltage feed back wire. I can ask when I pick it up. Might that cause the gauges to stop working and trans to enter limp modeI? (They hooked some type tester up at the battery that I believe checked the battery and alternator).
John Canfield
Site Team
The alternator's output is like Gary said is regulated but how that's accomplished varies depending on the vehicle or chassis manufacturer. Some alternators do not have a 'feedback' or control lead (wire) but are self contained. Some are regulated by the ECU or PCM (engine control unit or powertrain control module). I have no idea how that's accomplished in the P30 chassis.
Lots of weird electrical problems are caused by bad grounds (corrosion, loose connection, etc.)
I'm going to move this thread to the Motorhome board since it's a chassis problem and you'll get more eyes on the problem.
Lots of weird electrical problems are caused by bad grounds (corrosion, loose connection, etc.)
I'm going to move this thread to the Motorhome board since it's a chassis problem and you'll get more eyes on the problem.
Ex-Calif
Well-known member
Did they check all the fuses?
I am chasing an issue on a 2006-ish Sonoma right now. No shift (limp mode) and weird cluster gauge behavior and blown gauge fuse.
I have looked thoroughly for under dash shorts (driver "reported" seeing some smoke but I think it was a bad report). But one thing for sure is that it will drive fine for a week or so and then blow the gauge fuse and into limp mode.
I did a terrible thing and replaced the 20amp with a 25amp fuse and now the fuse doesn't blow but the same thing happens - limp mode and no gauges. I have cleared the fault codes twice now but the fault is still repeating.
So the latest weird thing is that the driver figured out that if he fiddle with the odometer reset knob (i.e. pressing it in to "reset" position and wiggling it, all the gauges come back to life!
I have told him my latest theory is the gauge cluster has some sort of weird board short and he is gonna have to find a flexible cheap mechanic who is willing to buy a wrecking yard dash cluster and replace the whole cluster.
Don't know if that is related to your issue but I wanted to share it out there in case any of your symptoms are similar.
PS - Be careful when you talk to mechanics - My driver took it to one mechanic and he advised it needs a new transmission - Didn't even tell the driver about limp mode - LOL...
Another neighbor told him the no shift was because he needs a new tranny filter and tranny flush!
I am chasing an issue on a 2006-ish Sonoma right now. No shift (limp mode) and weird cluster gauge behavior and blown gauge fuse.
I have looked thoroughly for under dash shorts (driver "reported" seeing some smoke but I think it was a bad report). But one thing for sure is that it will drive fine for a week or so and then blow the gauge fuse and into limp mode.
I did a terrible thing and replaced the 20amp with a 25amp fuse and now the fuse doesn't blow but the same thing happens - limp mode and no gauges. I have cleared the fault codes twice now but the fault is still repeating.
So the latest weird thing is that the driver figured out that if he fiddle with the odometer reset knob (i.e. pressing it in to "reset" position and wiggling it, all the gauges come back to life!
I have told him my latest theory is the gauge cluster has some sort of weird board short and he is gonna have to find a flexible cheap mechanic who is willing to buy a wrecking yard dash cluster and replace the whole cluster.
Don't know if that is related to your issue but I wanted to share it out there in case any of your symptoms are similar.
PS - Be careful when you talk to mechanics - My driver took it to one mechanic and he advised it needs a new transmission - Didn't even tell the driver about limp mode - LOL...
Another neighbor told him the no shift was because he needs a new tranny filter and tranny flush!
Solved! (I hope). It was a 15 amp gauges fuse under dash. Replaced it and everything works. I can’t believe this single fuse affected the gauges, marker lights, engine battery charging, and ECU transmission shifting control. I don’t know why the fuse blew, hopefully just because it was old, we’ll see. I guess my lesson is to always check the fuses first. Thanks to all who responded. It was a great help. John
Last edited:
Ex-Calif
Well-known member
Yeah - That fuse sounds like the one I was talking about. It drives a lot of systems.
udidwht
Well-known member
You also want to look at all the cable connections at the batteries. Remove and clean them well. Also locate and remove the ground braid cable for the engine to chassis ground. This is especially true for the older OBD-1 engines such as your TBI.
Ray-IN
Well-known member
One of these GM chassis links is to the electrical schematics;
GM MH chassis
GM MH chassis
