Grid heater malfunction on 93

[DThibault]

Cold weather brings out the problems. My 93 is the best starting Dodge on the farm but this morning it just barely caught. Thke wait to start light came on for may seconds with all the humming noises that go with it under the hood and the solenoid click at the end but the truck struggled to fire. It did start but ran very rough and the normal cycling of the grid heater was not there. No fluctuation of headlight intensity or bouncing of the amp gauge. Any ideas to help? Thanks

 

[JLEONARD]

Relays on the fender may be needing some attention. Check connections and grounds. How is the battery? Got enough in it for this cold weather?

 

[RSchwarzli]

I would agree. Check those relays. No dimming lights means no major power draw. That means no grid heater engagement and no heat to help the old girl start.

 

[DThibault]

So those two big relays that stand side by side are the ones to look at? What tells them to cycle, I'm assuming according to coolant temp as the duration of light dimming changes as the truck warms? I've got a cord running to it tonight because its supposed to be minus 10 F here in the morning. My tractor is in the shop as that thing is really finicky with the cold. When my son takes that to the woods tomorrow, I'll bring the old truck in to check the relays. I think I'm gonna need it by the end of the week. You should see that baby push snow. Thanks for the tip.

 

[RWherley]

The grid relays are run off the ecm witch reads the intake air temp sensor located in the top plate of the intake manifold, and that signal is read by the ecm turns the grids on and off till the intake air temp hits a pre set temp. you may also want to make sure both grids are working. there are 2 relays because there are 2 different grids its possible only one grid is working

 

[MMeier]

Strange, when I went to move my 93 today after work, I didn't get the wait to start lite either .

 

[JLEONARD]

Strange, when I went to move my 93 today after work, I didn't get the wait to start lite either .

That means you don't have to wait before you turn the key! LOL

 

[MMeier]

That means you don't have to wait before you turn the key! LOL

That, maybe the 76 * temperature had something to do with it also ?

 

[RSchwarzli]

The grid relays are run off the ecm witch reads the intake air temp sensor located in the top plate of the intake manifold, and that signal is read by the ecm turns the grids on and off till the intake air temp hits a pre set temp. you may also want to make sure both grids are working. there are 2 relays because there are 2 different grids its possible only one grid is working

Note that on the 1989 and 1990 trucks, there is no ECM. It is based off the sensor in the plenum saying yes, or no to the relays as I understand it.

As for the OP, if you are getting the clicking, the relay is tripping. Why aren't you getting power is the question.

 

[RSchwarzli]

So those two big relays that stand side by side are the ones to look at? What tells them to cycle, I'm assuming according to coolant temp as the duration of light dimming changes as the truck warms? I've got a cord running to it tonight because its supposed to be minus 10 F here in the morning. My tractor is in the shop as that thing is really finicky with the cold. When my son takes that to the woods tomorrow, I'll bring the old truck in to check the relays. I think I'm gonna need it by the end of the week. You should see that baby push snow. Thanks for the tip.

Not coolant. Has to do with the air temp in the intake. As the block warms up, the air going into the plenum has the ability to get warmed by the warming head. The cycle is therefore not as long and the lights dont dim as much as the length of pulse is shorter as it hits the "shut off heaters" temp sooner than on first start. My 1990 is bang on 50 F for the cycle. 50 is no heaters, 49 cycles them.