Heater no blowing hot?

Does it stay on defrost all the time? Do you know if it is automatic temp controls?

Sounds like a HVAC control unit problem not sending vaccum to the correct actuator. Or you are loosing vaccum at the actuator.

If your not sure how to test it, I would suggest going to a junk yard and getting a new HVAC control and seeing if it works.

Hi:
It could be the heater control valve or the heater core could be plugged not allowing coolant to circulate.

Yes the t-stat is easy to replace. However, before you do that, check something for me. If you are getting no heat at all, first make sure the coolant level is full. Next, with the engine running, hot, and the heater on high, feel both heater core hoses. Both should be hot.

Let me know what you find.
Joe

Did you check the thermostat and heater core. The coolant temperature sensor's job is to sense the engine temperature and the thermostat controls the temperature

To the best of my knowledge, it doesn't have a heater control valve. If it does, it would be on the supply side heater hose. If nothing is there, then you have a blend door that determines if you get heat. What I need to know is this, have you tried flushing the heater core as well as reveres flushing? Next, with the engine hot, heat on high, do both heater core hoses get hot?

Let me know.

Hey guys. Take a look at the speedometer pointer to see if there's a little stop peg the needle is against. By the late '80s / early '90s everyone went away from the too-reliable cable-driven speedometers and switched to electronic ones driven by a not-so-reliable computer. Turns out they have been rather trouble-free, but what can happen is they get hit with a voltage spike during other electrical repair work. This happens most commonly when connecting a new battery.

The speedometer is driven by a "stepper" motor. It is not a spinning motor with brushes like we normally think of. A stepper motor has four electromagnetic coils that are pulsed with varying voltage and polarity to create a movable magnetic field for the pointer to follow. You can identify these by the fact that they stay where they are when the ignition switch is turned off. They don't go back to "0" until the ignition switch is turned on next time.

The problem with those voltage spikes is if it causes the pointer to go more than halfway to maximum, when the ignition switch is turned on next time, it wants to go back to "0", but it looks for the shortest way to get there, and that will be clockwise. The pointer runs up against the stop pin and can't go any further.

There's three ways to fix this. The hardest method is to disassemble the instrument cluster to the point you can push the pointer counter-clockwise by hand. An easier method is to connect a scanner that can access the instrument cluster, and run the gauge test sequence. Typically that positions every gauge to its 1/4 scale, 1/2 scale, 3/4 scale, full scale, then back to "0". The speedometer will try to follow those steps, and once moving counter-clockwise is the shortest way to the target, the pointer will go there, then follow all the other gauges back down. Some cars can have the gauge test sequence initiated by pressing certain buttons in the right order without the need for a scanner.

The easiest method is to simply drive the vehicle faster than half the maximum speedometer scale. That doesn't mean 90 mph. Speedometer faces never have "0" and the highest number in the same place. Typically 0 to 180 will cover perhaps 270 degrees of sweep. In my minivan the highest reading is 125 mph, and 45 mph is right across from it. "80" is across from "0", so according to my sad story, if the pointer got stuck on the backside of the stop peg, I'd have to go 81 mph, then the shortest way to the target for the pointer would be to go counter-clockwise, then from there it would follow the computer back to its commanded positions.

Sorry that I don't do a good job of describing this fix. It's much easier to do than to explain it.