Engine/Transmission (1994 - 1998) Intermittent Heat in the Cab

[Bobcat698]

Basically what the subject says. .



I can turn the temp to FULL hot air with the dash vents, or any other setting (not AC) and the heat will work sometimes, and not work other times.



It isn't an issue of not being warmed up, because this happened even when pulling approx 12,000lbs.



I really need to get this fixed, as you know, its COLD in WI!

 

[JoeBioDiesel]

If you're saying that the blower works all the time, but it changes from hot to cold air, the first thing you need to check is the coolant level. If it's a little low the heat will cut in and out like that.

Joe

 

[Bobcat698]

If you're saying that the blower works all the time, but it changes from hot to cold air, the first thing you need to check is the coolant level. If it's a little low the heat will cut in and out like that.

Joe

I'll look into it. Thanks!

 

[Bobcat698]

Coolant is new. The level is good.

 

[KDHannink]

it could be your ignition swithch. i had the same thing happen, my heater and AC would not work at all. if I'm not mistaken, there was a recall on the ignition switch. check into that.

 

[Missouri Mule]

Could be your temp door... .

 

[Bobcat698]

Could be your temp door... .

Funny you say this. . I was messing with it on the way back from the Haisley pull in Summitville.



If you turn the temp all the way to cool, then to hot very quickly, it will get hot for a split second, then get a bit cooler when you hit the max heat setting.

It won't stay HOT or at least "full heat" at any setting though.

 

[BAnsley]

Sound like something is blocking the blend door or the accuator is bad. if it is vac. opperated get a hand held vac. pump and manualy operate it. and if it is electric motor find the proper test procedures from a shop manual to elimniate the switch from the motor and vise versa. And or loose/bad grounds. Good luck hope this helps!

 

[zstroken]

Don't you have some mod on your cooling system? Sounds like your transferring some heat over several minutes to the core, then as soon as you blow air accross it gets cold. What if you have it on cold, put it to hot, then put it back to cold, then immediately back to hot? I would turn it to hot with the blower off and see if the heater core hoses are hot.

 

[Bobcat698]

Don't you have some mod on your cooling system? Sounds like your transferring some heat over several minutes to the core, then as soon as you blow air accross it gets cold. What if you have it on cold, put it to hot, then put it back to cold, then immediately back to hot? I would turn it to hot with the blower off and see if the heater core hoses are hot.

I just have the rear port on the back of the block utilized and piped into the return hose coming from the firewall.



I can't even get decent heat in the cab grossing 19,000.

 

[zstroken]

That could be enough pressure to keep the coolant from traveling through the heat exchanger. Check both lines and see what the temp is of them. It you could easily block off the mod you did, that would eliminate that as a problem. DId it work before you put the mod on? Has it worked after you put the mod on? I would pipe it into the return line in the cooling system, not the return line on the heater core.