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1990 Cadillac Brougham Heater

Tiny
BCARTER1717
  • MEMBER
  • 1990 CADILLAC FLEETWOOD BROUGHAM
  • 5.0L
  • V8
  • RWD
  • AUTOMATIC
  • 125,000 MILES
What would cause the heater In my 1990 Cadillac brougham 5.0 liter to just quit working?
AC Is working on car buy the heater just quit all of a sudden. Engine thermostat seems to be working because
the water in the radiator is getting hot-like thermostat is opening properly. Blower switch and fan works on all speeds. I noticed the heater hoses going to heater core don't seem to be getting real hot to the touch. Not sure if this is normal. I would of thought the heater hoses would get hot like radiator hoses do.
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Thursday, January 30th, 2014 AT 7:07 PM

9 Replies

Tiny
MLDANIELS2000
  • MECHANIC
  • 227 POSTS
Check for control valve in heater core coolant lines. Check for operation. Also remove glove box and check air mix door for proper movement from hot to cold.
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Thursday, January 30th, 2014 AT 7:18 PM
Tiny
BCARTER1717
  • MEMBER
  • 5 POSTS
I was thinking the same thing and checked the heater control valve earlier. I noticed there is a fitting coming of the back for a vacuum line but there is no line to it. Looked around and couldn't find a hose anywhere that was off or looked like it went to it. Does it (control valve) have to have vacuum for it to work? How will I no if the valve is bad? It looks like the valve threads into the intake. Is that true and if so is it hard to take out?
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Thursday, January 30th, 2014 AT 7:42 PM
Tiny
MLDANIELS2000
  • MECHANIC
  • 227 POSTS
It needs a vacuum line to operate it. Look around the area for broken line. If none try to manually open valve if you can. Check then for heat. If that works you can use a tie strap or piece of wire to keep it held open. If possible please submit a photo of valve.
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Thursday, January 30th, 2014 AT 8:28 PM
Tiny
BCARTER1717
  • MEMBER
  • 5 POSTS
The control valve seems to be incased so I don't believe it can be opened manually. Any ideas? How do I know if its bad. I assume that if the hoses dont get hot then it must be stuck closed. Is it hard to replace?
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Friday, January 31st, 2014 AT 3:54 PM
Tiny
MLDANIELS2000
  • MECHANIC
  • 227 POSTS
Most likely stuck closed. Can you submit a photo of it please. No image on it I can find.
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Friday, January 31st, 2014 AT 3:56 PM
Tiny
BCARTER1717
  • MEMBER
  • 5 POSTS
Here is the pics. Got good vacuum going to it now but hoses still not getting hot
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Friday, January 31st, 2014 AT 5:35 PM
Tiny
MLDANIELS2000
  • MECHANIC
  • 227 POSTS
Should be attached by hose clamps. Usually just a 5/16" socket to undo clamp screw.
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Friday, January 31st, 2014 AT 7:45 PM
Tiny
BCARTER1717
  • MEMBER
  • 5 POSTS
Replaced heater control valve. Old one was definitely stopped closed. Car heater would still not get hot until I pulled the vacuum line off to the valve. I had just run it(vacuum) to it the other night after u said it needed vacuum to work. I teed off an old line to run a new line to valve. The old one had no vacuum line run to it even though there's a vacuum fitting on it. I don't understand how it works but it seems like when I hook up the vacuum line I ran to the valve the vacuum must be pulling the valve closed. The heater hoses are definitely getting hot now with the vacuum hose off the new valve and the heater is working great. It quits blowing hot when I hook vacuum to the valve. This seems very strange and not sure it's normal. Took off the new vacuum tee and line I ran and just left no vacuum to the new valve. Everything is working great but my question is will it hurt anything or the valve by not having vacuum running to it?
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Saturday, February 1st, 2014 AT 10:03 PM
Tiny
MLDANIELS2000
  • MECHANIC
  • 227 POSTS
Should be fine with no vacuum. Usually vacuum is supplied by the climate control/selector unit itself. You can just leave it off for now and when you need a/c just zip tie the valve closed. Valves come in 2 configurations; normally open and normally closed. You should be just fine with it in there and not hooked up. Just cap off the tee you put in place in the vacuum line so you don't have an engine vacuum leak.
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Sunday, February 2nd, 2014 AT 9:10 AM

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