QuestionI have a 98 Tacoma V6 Xcab pickup, 120k. Recently I started having problems with the heating system after a clutch replacement and some minor front suspension work (probably unrelated, but thought I'd mention it- the car was up and battery disconnected for several weeks). When the car is cold and I turn the temperture knob it is VERY stiff and clicks as I rotate it. Once the car has warmed up (about 15-30 minutes or so), the clicking usually goes away.
The heat is intermittent - it usually comes on and stays on reliably once the clicking has stopped and I can turn the knob smoothly. But occasionally it will turn on earlier, only to dissapear quickly. It takes longer if the car is just idling and not being driven.
My electrical system is under strain due to several accessories, but even turning those off does not improve the problem.
My guess is that the temp is controlled by a rheostat of some kind and it has broken... but that doesn't really explain why it gets better as it warms up. Any ideas on what to replace/test/look for? Thanks!
One other thing - I suspect my alternator may be failing. I read in another question you answered that a voltmeter should read 13.8V across the battery terminals with the engine running. What voltage would be diagnostic of a failing or failed alternator? Thanks a bunch!
AnswerCheck the heater control valve, it's located under the hood on the firewall, disconnect the cable from it and see if the problem turning the in dash control goes away, my best guess is that the valve is sticking and needs to be replaced.
A normally charged battery in good condition will read about 12.6 volts without the engine running, in order to keep the battery in a state of charge the alternator has to provide more voltage than battery voltage, in order to do this the alternator needs to put in at least 13.5 volts or the battery will not get charged back up and will drain from the electrical accessory current draw until it goes dead.
