Grid Heater Cycling When Engine Running

[Big_Bad_Dually]

My dad is having me post this problem about his 98. 4 12 Valve.
He said the engine was pulling down like the grid heater was coming on when he was parked in line at the bank. He also said that it wasn't his A/C and the motor was around 160-170 degrees and had been running for a while around town.

-Anybody else having this problem?

-Is there any was to put a switch on the relay to keep them from getting power like on a 6. 2L GM?

Brian

 

[DavidGardner]

Is he sure it wasnt the fan kicking in mine has done this when the temp gets real warm I can hear the fan going on and off like it was an electric fan on a gasser. Has happened pulling a long hill under load in a lower gear. Just a thought.

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95 slt, reg cab, 2wd, auto, BD exhaust brake, primelok fuel filter relocator, K&N air filter, Cat sleeping in garage by fire, TST 230-605 fuel plate, Bill Kondolay modified trans, 100k plus miles still going strong "Who says six in a row don"t go?

 

[LSMITH]

Brian, my 99 24V has done that from day one. I don't know exactly what it is for sure, but I think it is the power steering pump building pressure up for the brakes and steering. I think the 98 12V has hydraulic assist brakes too.

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99 2500 QC 4X4 AUTO SB 24V LARAMIE SLT 3. 5 LSD 285-75-16'S SPA Boost/EGT Everything but leather NRA Member Great Lakes TDR Member

 

[Timinator]

What does the volt meter do when this is happening? If it's not moving, then it's probably not the grid heater.

 

[gchas]

My '97 has had the same symptom since day one. The cylcling begins right away at start up. There is a very slight drop in RPM and the voltmeter fluctuates slightly. The owner's manual states, "After starting engine in ambient termperatures below 66 degrees F, some cycling of the voltmeter is normal during the first 3 minutes of engine running. " What causes this? Also, if the cylcling occurs after warm up, even if considered "normal", I would like to know what is the cause.




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'97 Ext. Cab 2WD 35K mi,5 Sp Man 3. 54, ISSPRO Pyrometer & Boost

 

[Big_Bad_Dually]

He didn't say what his volt meter was reading but described it like the grid heater was pulling down the motor through the alternator.

I don't know what it might be. My 95 doesn't do it. It could be the powersteering pump pulling it down too. BTW it does have hydralic power brakes.

Anybody have any ideas on a switch, anyway, for the grid heater?

Thanks
Brian & Harlan

 

[Missouri Mule]

gchas,
What causes this is cold temps. You have a temp sensor in the intake mainfold it sends data to the PCM which then gounds the relays(if works it like 96)which then send power to the air intake heaters(grid heaters).
Lets say( if it's set up like 96, below 60 degrees the heaters come on) truck/engine hasn't run in about 5 hrs well your temp inside the intake mainfold mite be 70 to 80 degrees( so the heaters will not pre heat) but it's 35 degrees outside. When you crank it up your engine is going to pull in 35 degree air which is going to kick on the post cycle until the turbo warms it up(the air).

I never had rpm drop because grid heaters just voltemeter.
If it isn't working right then you need to check out the sensor, relays, and corresponding wires/connections. Doubt very much it is PCM.

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Bill Thomas
Missouri Mule - 96 Wht 4X4 ST CC,5 spd, 3. 54, 8 ft bed, 1 ft high cheater boards.
99 Freightliner bl/wht FL60 ISB-5. 9 24v,215 hp,520 tq,6 spd, 3. 59 nsr,16 ft box, 19. 5 tires,Wt/gvw 11,000/23000