BobWatts

Recently one morning as I was leaving for work I found that my truck would not start. Batteries were dead. As I was hooking up jumper cables I noticed the rubber boots on the connections at the intake grid heater had melted.
Is the heater bad or the relays or both? How do check both?

----------------
Now playing: Rush - Limelight
via FoxyTunes

bob4x4

May be neither,I have seen many that were chewed by rodents

Bob

Dartmouth 12V

It is possible that one of your relays stuck open which caused enough heat to melt the boot and killed your batteries.

There are many other options as to what the problem could really be. If you keep having a dead battery and you know the batteries are pretty good, then I would check the relays with a multimeter.

The actual heating elements don't really go bad very often since they are just resistors.

infidel

Same here, in fact almost every one of the hundreds of trucks I've worked on.
Don't know what it is about the boots that thrills the suckers.
They also like to peel off the underhood insulation and stuff it in the air box.

BobWatts

Rats! I said melted not chewed. As Dartmouth 12V said it sounds like a relay problem. But I still wonder if the heater grid was damaged. Can anyone tell me how I would check it out before I remove it? Right now I have the cables disconnected and have not had a problem with the batteries dieing.

Dartmouth 12V

If you have access to a multimeter, check the resistance across the heating element. I don't have the power value in front of me right now and I can't remember it but you should be able to figure out the resistance value using P=IR and V=IR. If the resistance is close to this, I wouldn't worry about it. If you have a much higher resistance, you are getting a short and if it is basically zero, you have an open circuit.

infidel

It would be very hard to burn out the grids. Resistance across them will be very low, my guess is under 10 ohms.
Sounds like your relay(s) are stuck closed. It would be very rare for both to stick at once. Relay can be replaced with a $10 Ford starter solenoid availible at any autoparts. Get one with a non-grounded case or install a grounded one with the case isolated from ground.

If both relays are opening and closing but still staying on too long the problem is likely your intake temp sensor.

patdaly

Also, the bets price I found a year agow was from rockauto.com

Standard brand part, it came with the OEM part number on ot.