Giving the Heater Solenoids a Tune-Up

I currently own a 91.5 Dodge CTD and these photos and notes are from working on that truck.

All the images on this page can be clicked to view the larger version of the picture.

Heater Solenoid function.

A few pages you might find interesting describing pre-heat and post-heat cycles. I would think these manuals are way outta print and hopefully nobody minds me adding these. If they do they can contact me and i'll remove them.

Service Manual Sup 14-4

Service Manual Sup 14-5


The solenoids are easy to take apart. Cleaning the contacts is a breeze and will hopefully lengthen the life.

Here's a shot of the tools used for the project.

In order to remove the solenoids from the truck you need to do the following.

  • Remove the 2 nuts on top of each solenoid and disconnect the heavy black wires attached to the tops of the solenoids. These run from the solenoids to the grid heater at the area where the intake tube meets the intake manifold. Only remove the solenoid ends of the wires
  • Remove the 2 small plugs on each solenoid. Check their condition and clean if necessary. You can also adjust the tightness of the plugs by gently squezing the plug with needle-nose pliers
  • Remove the 3 bolts that retain the solenoids to the bracket
  • Taking a straight edge screwdriver, slowly and carefully pry the tabs on the solenoids bracket which hold it to the plastic casing. Pry them back just enough to remove the bracket from the case. Remove the bracket and gently remove the gasket. You'll be reusing it.
  • Below is a photo of one of the solenoids removed from the truck with the tabs out

    The relays come apart easy enough, but caution must be taken so you don't damage the connections from the small terminals to the coil. This is done by backing off the nuts on the small terminals about 1/8" and taping them down into the case. They are seated in the plastic slightly and this allows them to pop down from the recesses without breaking the leads running from the terminals to the coil

    Once the small terminals are no longer seated in the case then remove the small nuts from the terminal posts.

    Using a pair of needle nose pliers grip the metal sides of the coil and gentle work the coil out of the case. Alternate sides to wiggle it loose. DO NOT grab the coil in the center or you will risk breaking the windings of the coil and ruining it. Also watch that the small terminals are following along with the coil and all 3 are coming out together.

    When pulling the coil from the case be on the lookout for the small spring inside the case. This returns the coil back to it's resting position when power is removed and is important.

    Here's a look at all the parts layed out. Note I broke one of the connections on the first relay. Luckly it broke at the terminal and I soldered back on. that's why I say be careful :)

    Remove the 2 nuts holding the 2 top terminals and remove them from the case.

    Here's a shot of the contacts before cleaning.

    Use a fine file or fine grid sandpaper to clean the contacts. Make sure to keep the surface of the contacts level and not round the edges. If you using sandpaper I would recommend laying the sandpaper down on a smooth/hard surface and rubbing the contacts on it to help keep the surface flat.

    Below are the contacts after a quick cleaning. I didn't go crazy and remove every little imperfection. I prefered to leave more contact and have something to clean again if needed. Also more terminal means more area for the power and better heat dissipation.

    Remember to give the threads on the terminals a cleaning with a wire brush before reassembling everthing.

    After taking it apart, the reassembly process should be striaght forward. No real catches here. Just remeber the little spring!

    You might want to put a small skin of RVT on the gasket edges if your afraid of moisture getting in the solenoids. I left mine bare and and gently bent the tabs back over and then tapped them down with a small punch and gentle hits with a mallet.

    I might add some troubleshooting/testing to this page at a later date.

    Site created and maintained by Denis Hruza Last Edit: 12/15/04