Engine/Transmission (1998.5 - 2002) Grid heater test

[COlmsted]

How do I test my grid heaters to make sure they are working? The weather is getting colder and my truck starts hard in the morning. It starts and stalls a couple of times and then it will stay running but smokes ( white smoke) alot for about 30 seconds. Its a 1999 2500 with 40,000 miles. Over the summer I moved the lift pump with a Genos relocation kit, Everything was fine untill it got colder. Once started it runs and starts fine.

 

[Bob Wagner]

is your wait to start light working? once your truck is started you should see the alternater meter being around 8 volts

 

[Bob Cochran]

With mine you can see that they are cycling with the volt meter going up and down in conjunction with the grid heaters going on and off. I would say if they are cycling that they are working when the "wait to start" light is on as well. Just as you see the volt meter go down when they cycle you should see about 8 volts when they are on before start as Bob Wagner says and voltage go up when the "wait to start" light goes off.

 

[COlmsted]

It was in the 20's this morning and the truck started on the first try. It smoked alot and did not hit on all six cylinders for the first 20 seconds. The wait to start light was on and the volt meter was I believe 10 volts. It will be in the 20's again tonight so I will pay more attention to the volt meter while the wait to start light is on. Is there a relay somewhere that could be bad or do the grids burn out? I will try in the morning and let you know how I make out. Thanks for the info!

 

[Bob Cochran]

I don't know about your year but on mine the following applies. There is a 2 element grid heater that works independently. For this reason there are 2 grid heater relays mounted on the left wheel well. There is also 2 fusable links. The grid heaters can burn out but I doubt that is the cause it can be relays or fusable links. I sure hope this helps.

 

[COlmsted]

The wait to start light came on as usual and I watched the volt meter. It appears to be at around 12 volts and does not cycle like it used to. Truck started real hard and smoked alot, smoothed out in about 20 seconds. I will check the relays now and get back with results. Thanks!

 

[mhenon]

The wait to start light came on as usual and I watched the volt meter. It appears to be at around 12 volts and does not cycle like it used to. Truck started real hard and smoked alot, smoothed out in about 20 seconds. I will check the relays now and get back with results. Thanks!

That's what you want to do. Have someone turn the key on while you check for voltage (8-10 volts) comming out of the relay. If you get none you might have a bad relay. In your case it sounds like a loose or dirty connector somewhere.

Mike

 

[Bob Cochran]

If both relays, fuseable link etc. appear to be bad I doubt both would fail at the same time but I suppose it would be possible. The output that controls the relays I believe is from the ECM. Of course corrided, bad connections, and my all time favorite GROUNDS are a best possible problem and easiest and cheapist to fix to.

 

[CLamb]

How long does the light stay on when its cold outside? Should be on for a little while.

 

[WadePatton]

Plug that puppy in! Won't fix the heaters, but it'll sure help the startup.

 

[COlmsted]

With a test light I have juice before and after the fusable link. I have juice going into the relay (both) but no juice coming out when the start light is on. I will try cleaning the conections tomorow and see what happens. I agree with Bob that maybe the ECM is not getting a signal that its cold thus no grid heaters. I will keep everyone posted

Thanks, Charlie.

 

[mhenon]

With a test light I have juice before and after the fusable link. I have juice going into the relay (both) but no juice coming out when the start light is on. I will try cleaning the conections tomorow and see what happens. I agree with Bob that maybe the ECM is not getting a signal that its cold thus no grid heaters. I will keep everyone posted

Thanks, Charlie.

Pull the two wires controlling the relays. One of them should get 12 volts (from the ECU I suppose) to activate the relay. The other is the ground. That will tell you right there if the ECU signal is going to the relay.

Mike

 

[Bob Cochran]

The wait-to-start light time varies depending on how cold it is.



I am wondering will a bad AIT cause the grid heaters to not work? I would think so but not sure anybody else have a thought on this?

 

[Katmandu]

The wait-to-start light time varies depending on how cold it is.

I am wondering will a bad AIT cause the grid heaters to not work? I would think so but not sure anybody else have a thought on this?

What is an AIT ??

Are the grid heaters "supposed" to STOP cycling AFTER the engine is warmed up OR do they cycle continuously depending on the outside temperature ??

Is there a thermostat for the grid heaters or are they on a timer ??

 

[COlmsted]

Got out of work late so time was short to work on the truck. I did what Mhenon suggested and when the wait to start light is on I have power to the small wire going to each relay but no power going out of the relay to the grid heaters. It seems that the ECU is calling for the grid heaters but the relays wont trigger the grids. I will clean all conections tomorrow and report. I believe when the engine is cold the grids will cycle but will stop cycling when you start driving and hit 15 mph or more. Bob, I agree that the ECU gets readings from the Intake air temp sensor and along with the water temp reading sends a signal to the relays for power to the grids. Do you think the local NAPA store has the relays if I need them? Thanks again everyone I will report tomorrow. Charlie

 

[COlmsted]

I cleaned all the connections and it didnt help. I am going to change the relays unless anyone else has a better idea. I will keep you posted . Thanks for the help.

 

[COlmsted]

I ordered the relay's from Dodge for $70. 00 + tax. Installed them today and all is good again. I asked the parts guy if they sell alot of them and he said no, maybe a couple a year. Thanks again for all the advice! Charlie.

 

[mhenon]

I ordered the relay's from Dodge for $70. 00 + tax. Installed them today and all is good again. I asked the parts guy if they sell alot of them and he said no, maybe a couple a year. Thanks again for all the advice! Charlie.

I'm still struggling with what caused both relays to go at once. Unless you've been working on one grid for awhile which would put an extra load on the working grid causing it to fail too.

Anyway, glad you got it worked out.

Mike

 

[CLamb]

I think the heaters cycle anytime your going less than 15mph AND the intake air temp is less than 60*.

 

[WadePatton]

... I asked the parts guy if they sell alot of them and he said no, maybe a couple a year. Thanks again for all the advice! Charlie.

That's what they say about LP's and VP44's and headlight switches too.



Glad you gotter fixed.