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Discussion Starter #1
Hi guys; i haven't been on the forum in quite a while... We have an '88 Fleetwood Brougham with heat problems. When the blower is turned on no heat comes out. When the defroster is on it comes out warm at best. When the system is shut, but the temp. is set at 90 degrees, it comes out warm at highway speed..
The books I'm looking at don't show if the car has the heater control valve that the 70's models had to keep hot water from entering the heater core when the AC is on. And I don't see one where it used to be located on the firewall. I know the 90's era Caddy's had an actuator door under the glove box but I can't tell if the 80's models have them too. The only reason I wasn't suspecting a clogged heater core is because of the hot air coming out when the blower is off and traveling at highway speed...Any ideas/help from you guys would certainly be appreciated as it has me stumped and I really don;t want to pull out the heater core if that isn't the problem.
 

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70 Deville 78 Seville 92 Deville 03 Deville
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I'm pretty sure this car is supposed to have a heater valve at the back of the engine. Trace the heater hoses back to it and while you're at it see if they are both getting hot.
 

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Start with the basics this order.
1. Is the engine coolant getting to operating tempiture with it ideling for about 10 minuets.
Without a scanner or laser temp gauge you can at best use your hand.
Around 195 F inside the hose wont burn you to just touch, but too hot to hold on to.
Holding a kitchen thermoeter against the hose is another way, but it may read slightly lower than actual.
If not, you may have a bad thermistate or fan clutch.

2. Are both the heater hoses hot. One a bit hotter than the other is normal.
If not, check the heater valve. It's a simple in out vacuum controlled valve on the heater hose.
The side lever of the valve should change position as you ajust from the coldest to hottest setting.
If you don't see it moving, try removing the hose an moving the lever by hand. Better would be to apply vacuun to see if you can get it to move.
Even if it mooves the inside valve flap could be broken or clogged.
Upper radiator hose hot but heater hoses still cold after heater valve operation confermed, then it would be a clogger heater core (or valve), or air pocket in heater core.

3. If hot coolent is flowing through the heater hoses then you need to look at the hot / cold air door system (behind glove box) and the system that controls it.

In the end a thermostate, coolant change, replace old hoses, tighten hose clamps, flush system (engine, radiator, & heater core), checking freeze point is basic maintenance.
Thermostates can be had for as low as $0.85, gasket $0.40, & heater valve $20. Most costly thing now is the antifreeze.
 

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Discussion Starter #5
Thanks LV. My husband is working on it now..we noticed only one heater hose hot. So we disconnected the A/C compressor to make sure that wasn't running; one hose was still cold. I hadn't noticed the heater valve on this car due to it's being screwed into the engine as opposed to 70's models that had it on the firewall. But now I see it. We're now pretty sure it's a clogged core as last year we did have to change the radiator as it was actually falling apart. Never saw that happen on the 70's radiators! .. So he's changing the core as we speak and I'll keep it posted how it goes with that being the problem... Thanks again (y)
 

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90 Brougham 5.7, 05 Deville DTS
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Thanks LV. My husband is working on it now..we noticed only one heater hose hot. So we disconnected the A/C compressor to make sure that wasn't running; one hose was still cold. I hadn't noticed the heater valve on this car due to it's being screwed into the engine as opposed to 70's models that had it on the firewall. But now I see it. We're now pretty sure it's a clogged core as last year we did have to change the radiator as it was actually falling apart. Never saw that happen on the 70's radiators! .. So he's changing the core as we speak and I'll keep it posted how it goes with that being the problem... Thanks again (y)
It has been some time since I had my 307 Brougham, but I think the heater control valve was located by the transmission fluid dip stick.
As the other members have suggested check out the other items as well.

good luck
 

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Discussion Starter #8
just to update - hubby changed the heater core a couple of days ago with no more than a slight bit of cursing. I even had a can of body/seam sealer laying around to reseal the cowling. It was definitely clogged, as I couldn't blow through it but the new one could be blown through easily. That control valve is also bad. And why not, if the core was full of junk why would that old valve be full of corrosion also. Quick question for anyone who knows - what does the switch/electric connection on the heater control valve do exactly? Older Cads didn't have any electric going to the valve; just vacuum.
 

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Discussion Starter #9
just wanted to thank everyone who responded to our heat problem...we got to the bottom of the problem. After changing the heater core and still no heat, we went for the heater valve. Low and behold, the valve was OK but the port entering it was clogged with old silicone. Someone back in another time, and possibly distant galaxy, got crazy with silicon on something and it got into the cooling system, clogging the port leading to the heater valve. We swapped out the valve anyway so we never have to try and get into that impossibly small work area again in the future and the heat is now so hot you could burn your hand next to the defroster. ..End of problem.. Moral of story - be judicious in the use of silicon when using it.
 
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