Engine/Transmission (1998.5 - 2002) grid heater

[RCrosby]

the last couple days it was 45 deg. in morning. engine stumble at start up had to hit starter a couple times. I'm not getting voltage to the heaters, right now it is 70 deg. no voltage to heater on air intake i am getting 8 volts signal to the coil only when key is on.

 

[B.G. Smith]

The grid heaters are wired as follows: Two grid heater relays with 12v to the coil at all times, the relay is closed when the ECM grounds the other side of the relay coil. A 12v cable comes from each battery to one of the relays so one side of the relay is hot. The terminal on the other side of relay has a cable going to one of the heaters. There are two heater coils with one end of each coil grounded to the engine. When ECM senses intake temps below about 60 deg. F it grounds the relay circuit which closes the contacts in the relay and activates the heaters. bg

 

[RCrosby]

just went check it,with engine down no power. big wire from top of coils to battery has 12.5v. small wire on side of coils has 0 volts, with meter on small wire when ignition is keyed it has 8.10 volts. its about 55 deg. still no volts to heater. thanks

 

[B.G. Smith]

There are two small wires on the relay I believe, you may be reading the ground side, (the one that goes to the ECM) If so then that is the reason you are showing less than 12v because there is some resistance in the coil winding. bg

 

[RCrosby]

I just went back and check, I disconnected the front wire on coil to radiator side and put meter on wire, and only getting 8 volts with the key on, and o volts at heater. both coils are the same.

 

[SAndreasen]

I have had some grid heater issues earlier if you can find my posts sticks gave some very helpful info on how and what to check

 

[RCrosby]

Got it working, load tested the batteries, one was weak, I replaced the batteries back in 10/07 & one relay for grid heater was bad. change both batteries and both relays, picked up relays w/brackets perfect fit from napa 75.00 bucks. 12.5 volts crossing relay and it is cycling on & off.

 

[SAndreasen]

Glad you got it fixed they sure make a big difference when they are working don't they

 

[RCrosby]

still working good