1993 K2500 Heater Issue

My 1993 K2500 heater will only blow cold air. The fan works great, the pickup comes up to temperature just fine and the controller seems to be working. Any suggestions?

Thanks,

Bob

My 1993 K2500 heater will only blow cold air. The fan works great, the pickup comes up to temperature just fine and the controller seems to be working. Any suggestions?

Thanks,

Bob

Check heater hoses for circulation threw heater core.

Feel both heater hoses for being cold,warm or hot to the touch.
Tell us what they feel like?

Does everything else work on AC/heater?
Like vent control and AC?
Will the tempt door motor move when going from cold to hot setting?

I replaced the thermostat and now the pickup won't heat up past about 140 degrees. Always heated up to around 190 before no matter what it was being used for. Will this be a problem?

I checked the hoses to the heater core and they are barely warm to the touch.

Bob

Rust tends to build up and clog the hot water flow usually at the fire wall connection, right where the rubber hose's connect. Remove and inspect both ends of the hose nipples.

For a heater to work good yiou need tempt at 195 degrees.
And as said pull them heater hoses and check circulatiion and heater core circulation.

Thanks for the replies. I am no mechanic, so hope this doesn't sound to dumb. What is the best way to check for flow thru the heater core?

Thanks,

Bob

Also, I have the dash apart mand can see the vents opening and closing for the defrost and other vents, but where is the vent located for the hot to cold setting?

Thanks again,

Bob

Thanks for the replies. I am no mechanic, so hope this doesn't sound to dumb. What is the best way to check for flow thru the heater core?

Thanks,

Bob

Best flow check is to feel heater hoses.
If one hot to touch and other one hot you have good flow.

Also, I have the dash apart mand can see the vents opening and closing for the defrost and other vents, but where is the vent located for the hot to cold setting?

Thanks again,

Bob

The flaper door is inside.
The actuator motor [small black electrical box] is upper center fron on heater housing.
You should be able to hear and feel it movingb cold to hot.

Hey Guys:

Thanks again for all the great replies. I took the hoses off the heater core and lo and begold, a big piece of junk blocking one of the inlets. Cleaned it out and now I've got heat. Thanks again, you guys are great!

Bob Jensen

Hey Guys:

Thanks again for all the great replies. I took the hoses off the heater core and lo and begold, a big piece of junk blocking one of the inlets. Cleaned it out and now I've got heat. Thanks again, you guys are great!

Bob Jensen

You are welcome.

If there was junk there there may be more someplace.
I would flush system and back flush heater core.

Junk in coolant system is usually caused by no servicing coolant.

Good idea to change coolant every 3 years or 50K

Another source of "junk" can be the cheap cast zinc heater hose connections coming from the water pump and intake manifold. Especially for the one screwed into the steel pump, they can corrode internally and chunks break off, clogging up whatever's downstream. I recently replaced the water pump connector because it developed a pinhole leak. It had corroded all the way through and most of the threaded portion was either gone or broke off when I unscrewed it.

Test yours with a magnet to see if it is made of steel. If the magnet doesn't stick, it's zinc. Be gentle when removing it. If it breaks off inside, you'll have to remove the pump and flush all the junk out. Hope this helps!