My 1994 mazda 626's temperature gauge went to hot(H) and it had stopped blowing out hot heat. At the same time the battery light stayed on. There didn't seem to be a problem with the battery until days later. I was told it may be the alternator, but I don't understand what that would have to do with the heat and running hot. Especially since both happened at the same time. Both meaning on H and battery light coming on. The person I took my car to didn't seem to have an answer for both. I did get a new battery but that didn't change the temperature and heat situation, and the battery light is still on. An answer for both problems-which I believe is one problem causing the other-would be appreciated. Thanks.
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Re: No heat...Needed new battery
Well #1 with the gauge going to hot and no heat,10 to 1 it's a bad thermostat, stuck in the closed position.If you drove it like that for any length of time, with it hot, other things can get damaged.Change the thermostat, then have the alternator checked to see if it's charging.The meter should read 13 to 14 volts or more.
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Check that the two hoses of the heater core at the firewall are getting hot. If both are not hot, then the heater core is plugged up. Try to flush in this case to free up sediment. If that doesn't work, maybe a new heater core is required, assuming that the blend door is operating correctly, and diverting hot air to the defrost or front vents.
A common problem with 134a systems. In a 134a charged system a higher pressure is needed and typically this is best achieved at higher rpms. You may just need to charge the system, there are several options to do this yourself, however, you may want to have the system checked. I would try self charging the system first. If you choose this option make sure you get one that has a gauge indicator so that you don't over charge the system as this is dangerous and can damage your system.
New water pump.... new timing belt.... new radiator cap... but the idiot mechanic has not done the obvious.
1. Change the coolant thermostat located under the hose fitting on the manifold where the top radiator hose connects to the engine.
2. Check the radiator fan switch for proper operation. When in doubt change it out. A $30.00 switch isn't worth risking a complete engine overhall.
3. Do a compression check on the engine to make sure all cylinders have close to the same amount of comression. Overheating can cause head gaskets to weaken and fail. Performing the compression check would verify that both the cylinder head, valves and head gasket are still in good working order.
4. (Applicable only to cars with a belt driven fan) Does the fan have a fan clutch? I did not look it up yet. If it does then the fan clutch can also be a problem if it is not turning the fan when the engine is hot.
For cars with an electric fan the switch in step 2 applies as does checking the fan for proper operation.
5. Fire your mechanic! If there is one thing I hate it is a mechanic that only does half the job vs checking out all possible causes! Your car should have never left the shop in a state that it could over heat AGAIN. Time to have a chat with she service manager and the service managers' boss! They owe you some free labor!