Bad control unit?

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Bad control unit?

Postby Jelmer » Mon Feb 26, 2018 1:50 am

Yesterday I started the truck in the morning and the check engine light came on right away. It also didn't charge, the gauge showed 10 volt.
I checked the battery when running and it is 12v.

Since we bought the truck back in 2009 it always did the next thing:

When you cold start the truck the volt gauge shows around 10v, than after 2-3 seconds it starts charging, than stops charging again after 2-3 seconds. This goes on for about 2 minutes and than it keep the volts at 3/4 on the gauge.
When warmed up it always keeps the gauge at 3/4.

After reading a bit I think the control unit is bad so I think I will convert it to a old style regulator.

How do I get the check engine light out?
Greetings from the Netherlands where there are only 2 or 3 1stgens!
93 D250 Cummins, G360, 4" stainless exhaust, BHAF, DennyT stage 2 pin, 3200rpm governor spring, 12cm housing, rest stock.
03 VW Bora 1.6
83 Datsun Laurel 4.5 32v V8
84 Nissan Patrol 2.8i
Jelmer
fuel screw!!!!
 
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Re: Bad control unit?

Postby Richie O » Mon Feb 26, 2018 5:11 pm

The up and down voltage when cold may be the grid heaters going on and off. They drag some power. I had a solenoid stick on once too and the grid stayed on, it dragged the voltage down. I shut the truck off and I could hear the grid whining. I just unplugged it and never looked back.
1989 W250 727, 3.07 L/S, S300, P/S Intercooler, Stans exaust, Pump adjustments, 127k miles,297 hp
1993 W250 extended cab, rag, 4.10 l/s, 6x16's, HTT 62/71/14 piston l/p, Isspro EV series tach, fuel pressure, boost, oil pres, water temp, volt, pryo, 132k/ 301 hp
1992 W250 with NV4500, 3.54's, 16cm 60mm GDS H1C, ground stock cone, Isspro tach, pryo, boost, fuel pressure, slow, rusty, dented,180k
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Re: Bad control unit?

Postby Richie O » Mon Feb 26, 2018 5:13 pm

As far as not charging at all, maybe the crank sensor. My 93 did that and the sensor was dead. If its not reading rpm's it won't charge. My 92 lost its brain and I converted that to old school regulator. Now it has the dodge voltage cycle. Drives me nuts. I have done all the so called fixes and it still does it. Lights go bright dim bright dim 2 times a second. :roll:
1989 W250 727, 3.07 L/S, S300, P/S Intercooler, Stans exaust, Pump adjustments, 127k miles,297 hp
1993 W250 extended cab, rag, 4.10 l/s, 6x16's, HTT 62/71/14 piston l/p, Isspro EV series tach, fuel pressure, boost, oil pres, water temp, volt, pryo, 132k/ 301 hp
1992 W250 with NV4500, 3.54's, 16cm 60mm GDS H1C, ground stock cone, Isspro tach, pryo, boost, fuel pressure, slow, rusty, dented,180k
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Re: Bad control unit?

Postby PToombs » Mon Feb 26, 2018 5:37 pm

X2 on the grids making the gauge go up and down. I would start it and wait until the grids stop going on, then check the voltage. Should be about 14 at the battery if it's charging, 12 or so if not. If it's showing 13 or so, turn on the lights and heater fan then check again. If the voltage drops when you have stuff on then the diodes are bad and it's time for an alternator.
pete

Just enough power to break everything behind the crankshaft.
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14mm rotor
 
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Re: Bad control unit?

Postby Jelmer » Tue Feb 27, 2018 12:29 am

It is not charging, the multimeter shows 12v when running. I also didn't hear the grid heater relays when I started it this last time.
Does the control unit turn on the grid heaters if it doesn't "see" the engine running? (with a bad crank sesnor)
Greetings from the Netherlands where there are only 2 or 3 1stgens!
93 D250 Cummins, G360, 4" stainless exhaust, BHAF, DennyT stage 2 pin, 3200rpm governor spring, 12cm housing, rest stock.
03 VW Bora 1.6
83 Datsun Laurel 4.5 32v V8
84 Nissan Patrol 2.8i
Jelmer
fuel screw!!!!
 
Posts: 52
Joined: Thu Jan 15, 2009 7:40 pm
Location: Netherlands
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Re: Bad control unit?

Postby PToombs » Tue Feb 27, 2018 4:56 pm

Pretty sure it doesn't care about the sensor to run the grids.
pete

Just enough power to break everything behind the crankshaft.
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PToombs
14mm rotor
 
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