Hello,
My heater on my 99 diamante(verada-magna) does not work. The ac works fine, but no heat! What could it be? I seached the forums in an out and it and cannot find anything on this! It doesnt seem to be heater core. Could it be thermostat, or old coolant? How do I check the thermostat? Let me know of any fixes. Thanks. :cry:

I don't know anything about third Gens but the principle is the same for most car heaters. When you set the heater controls to hot, hot coolant from the engine should run through the heater core. The blower sends air across the heater core and you should get warm air coming out into the cabin.

You said you are getting cool air so the blower must be working.

Since the air is not hot, most likely the coolant is not circulating through the heater core. The core or one of the heater hoses could be blocked or the valve (tap, stop****, whatever it is called) may not be functioning.

On most cars, the stop**** or valve is operated by a rod connected to the heater temperature slider or control knob. Maybe the rod is disconnected or has fallen off.

I doubt whether the thermostat is the problem because you would have noticed problems with the engine either overheating or taking too long to warm up, depending on whether the thermostat failed shut or open.

LOL @ word filter on stop****

is the engine getting hotter than normal might be an indication of more serious trouble water pump might be broken or a valve has locked shut and water isnt actually flowing around

stop****???

stop****???

Stop_c_o_c_k_! (I thought it was funny too).

dunno how the veradas work but if u dont turn the ac button off on mine wen u wanna use the heater it doesnt get very warm at all

I don't know anything about third Gens but the principle is the same for most car heaters. When you set the heater controls to hot, hot coolant from the engine should run through the heater core. The blower sends air across the heater core and you should get warm air coming out into the cabin.

You said you are getting cool air so the blower must be working.

Since the air is not hot, most likely the coolant is not circulating through the heater core. The core or one of the heater hoses could be blocked or the valve (tap, stop****, whatever it is called) may not be functioning.

On most cars, the stop**** or valve is operated by a rod connected to the heater temperature slider or control knob. Maybe the rod is disconnected or has fallen off.

I doubt whether the thermostat is the problem because you would have noticed problems with the engine either overheating or taking too long to warm up, depending on whether the thermostat failed shut or open.


I just started looking around a bit more and found that the upper radiator hose is way hotter than the lower radiator hose. I brought the engine to operating temp and the upper hose is hot, but the lower hose is cold (room temp).... What symptom is this? Is this a thermostat stuck closed or something? I would just replace the thermostat and see if that fixes it, but the thermostat seems hard to replace...anybody ever replace there own, any how to? Thanks for ALL HELP!

Yes, that does sound like a problem with the thermostat stuck closed. I just replaced mine (on a 1st Gen, not a 3rd Gen). It took me about 5 minutes max. You need the thermostat and a gasket for it - about $20 all up. You are supposed to drain all of the coolant first but since the thermostat housing is towards the top of the cooling system, I didn't. I lost perhaps half a litre of coolant.

Undo the upper radiator hose at the thermostat housing. This is where you will lose some coolant if you haven't drained it first.
Then undo the bolts of the thermostat housing, take the top off and remove the thermostat. Remove the old gasket. You may have to scrape it off to ensure that you get a good seal with the new gasket.

Put the new thermostat in, making sure that is facing the correct way. There should be a diagram on the packet showing which way it is supposed to go. It may still work the wrong way round but certainly not as efficiently. Replace the gasket and bolt the thermostat housing on again. Do not overtighten. Connect up the radiator hose and tighten the clamp on it. Top up or refill the coolant. That's it.

Yes, that does sound like a problem with the thermostat stuck closed. I just replaced mine (on a 1st Gen, not a 3rd Gen). It took me about 5 minutes max. You need the thermostat and a gasket for it - about $20 all up. You are supposed to drain all of the coolant first but since the thermostat housing is towards the top of the cooling system, I didn't. I lost perhaps half a litre of coolant.

Undo the upper radiator hose at the thermostat housing. This is where you will lose some coolant if you haven't drained it first.
Then undo the bolts of the thermostat housing, take the top off and remove the thermostat. Remove the old gasket. You may have to scrape it off to ensure that you get a good seal with the new gasket.

Put the new thermostat in, making sure that is facing the correct way. There should be a diagram on the packet showing which way it is supposed to go. It may still work the wrong way round but certainly not as efficiently. Replace the gasket and bolt the thermostat housing on again. Do not overtighten. Connect up the radiator hose and tighten the clamp on it. Top up or refill the coolant. That's it.

Okay, so it seems definite its the thermostat if the bottom hose is cold...? It looks like on the 3rd gen, it is a pain to replace the thermostat. It is bolted on the end of the lower hose and looks like I have to remove the air box assembly and a few more various hoses and things to get to the 3 bolts. Has anyone done this before? Let me know. Thanks.

Err..AFAIK hot water comes out of the top of the engine, trickles down through the radiator and is cooled on the way. So lower hose should be colder.

As silly as it sounds, check the right hand knob on your vent controls. It's supposed to blow cold air in one position, and hot air in the other. :badgrin:

Look in the manual to confirm.

I think the real question that needs to be asked it WTF do you care about your heater for IN THE MIDDLE OF SUMMER?!?!?!?!?!?!?!?!

I think the real question that needs to be asked it WTF do you care about your heater for IN THE MIDDLE OF SUMMER?!?!?!?!?!?!?!?!

Um - probably because he doesn't live in Australia...