Engine/Transmission (1998.5 - 2002) Dead Heater Grid?

[Newf Limo]

My truck has always started in the winter, and fast. I never have had to plug it in, even when sitting in -20 for a few days. Two cycles of the pre-heater and it fires up in 3 revolutions.



As it gets colder out, it has been getting near impossible to start.



Yesterday it was 17 degrees and it didn't even try. The pre-heat cycles, the light goes out and I can hear the relay click, but you would think that I had run out of fuel. I plugged it in for an hour (which isn't really long enough) and it started reluctantly and chugged like a crochety old dump truck for about 20 seconds.



Does this sound like a burned out heater grid? Are they expensive? Is it a dealer item only? And am I going to be cussing while replacing it the way I did when replacing the Crank position Sensor? ( Even as an agnostic ex-catholic I feel I should go to confession after THAT one. !)



I appreciate the help folks, and Happy Holidays.

 

[PC12Driver]

The easy way to see if they're working is to watch the voltmeter. The grids will pull it down to 10-11 volts depending on battery health. Or watching for big swings in the voltmeter (or dimming lights) as the truck warms up and the grids are still cycling (until 3 minutes or 17mph, whichever comes first). If you don't have the voltage drop, then it's time to break out the multimeter and see what's getting power.



I'd start by checking voltage at the grid when you first turn the key on (when the WTS light would be on). There are two nuts on one side of the heater grid that clamp the power leads in place (where the intake horn hits the cylinder head). Those should have about 12v when the WTS light is on. Each one is a separate circuit (two heating elements), so test each one separately. On the opposite side of the grid block is the ground lead that you can put the black lead of your multimeter to.



If there isn't power at the grid, then move back to the relays. They're a bit of a reach, but not hard to get to. You can turn the key off for this one. Follow the two cables from the grid back, or if you look down from the driver's battery, sort of behind the intake tube from the intercooler to the intake horn, you'll see the pair of heater grid relays. Each one will have two small posts with light wires and two large posts with the heavy cables from the battery to the grids. First, make sure the light wires are pressed on to their studs (although if they weren't, I think you'd get a code). Then check for voltage. The black wire from the multimeter goes on the negative terminal of the battery, and then test to each one of the studs that have the heavy cable attached. The battery side of the relay should show about 13v, and the grid side should be zero. If this checks out, then it is probably the relays that are bad and not closing to get power to the grid. If you don't have power to the relays, then it would be the fusible link (cable) between the relays and the battery.



There isn't much to the heater grids, and they're pretty heavy duty, so I'd be surprised if it was the grids themselves. They're easy to replace though (four bolts, three nuts, and a hose clamp), and cost around $85. If it's the relays, they're still easy to replace, but there's a bit more reaching involved. There was a writeup on those a few years back here.



The stock relays are pretty frail. I just replaced mine (sticking closed) and dissected the old ones, and the contactors were almost burnt away. In my case, one was sticking closed. Now that can get exciting.



Good luck, and let us know what you find!

 

[Newf Limo]

Hey PC12



I see now my thank you post didn't actually post



That is embarrasing!



I usually do all the work on my truck myself. Before your post, I didn't even realize that A) Those two wires off the battery go to relays. B) Those relays go to the heater grid! What a bone head!



I have had a corrosion issue since i replaced my batteries. It donned on me that since I was pretty sure that my CB/10Meter radio faded out (power wise) i knew that the poser terminal at the battery was being eaten. So, it stood to reason that the newly identified Relay wire terminals were suffering the same fate (on the other battery). Sure enough, the unsulater sleve was buldging with crap. I replaced the terminal with a marine grade terminal, and viola! Heater grid works perfect!



So, now I have a new post about Batteries causing excessive corrosion.



Thanks again, Merry Christmas, and I am going to verify that this makes it onto the board this time.

 

[Newf Limo]

Ok, there it is.

 

[PC12Driver]

Good deal - glad you're back in action.



BTW, a little baking soda (not powder) and water mixture will neutralize the acid eating away at those terminals. It might give you a bit more life out of them.

 

[Newf Limo]

Thanks, at one point I tried a can of coke just to try and get them clean, then finished with soap and water. Don't think that worked so hot though. I will have to try it. I am thinking of going by the Car Quest dealer and showing them what is going on. See if they just shrug their shoulders and say, that's nice, now go away.

 

[PC12Driver]

Yeah, you'll need to get a base in the equation (the baking soda) to neutralize the battery acid. It won't clean anything, and will make more of a mess, but it will stop the corrosion. Soap & water will just dilute the acid and effectively make more acid.

Old batteries? Or one older than the other? If one ages faster than the other, it'll throw off the balance between the batteries and one will continually overcharge and vent excessively.