Rear heat operation

Rear heat operation

Postby espionage33 [OP] » October 18th 2011, 3:46pm

Hello all,

Just wondering how the rear heat is supposed to act on a 1997 AWD Safari, Starcraft Conversion...

Currently, my rear heat only works when I have the front heat on the Defrost/Floor or Defrost only modes. Even then, it takes a VERY long time to get rear heat... Is the rear heat supposed to work regardless of what the front heat switch is doing?

I noticed a little radiator leak the other day, and when i took the cap off my whole radiator was filled with this brown crap. I had lost most of my fluid from this leak, so i put in a bunch of water, for a temp solution. Then i went to put in some actual anti-freeze (green stuff), to do this i started the car and took off a hose by the firewall so that the water would be pumped out. Well it came out in a pretty weak stream and was all brown, from the dirt in the system i assume. My plan is to use a garden hose to flush out the system until the water is clear again, i think it may be clogged up quite a bit.. My front heat works, but its not very good, also i think that brown crap has clogged up my thermostat, it doesn't seem to work quite as well as when i first installed it...

Also, im wondering if there are any vacuum lines, switches, or valves that control the rear heat, and how to diagnose them if there is a prob. Tips, advice?

Thanks in advance!
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espionage33
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Re: Rear heat operation

Postby chevymaher » October 21st 2011, 1:33am

Run some radiator flush in it for a week to break up the brown garbage.Then flush with fresh water.Refill and check in the radiator a week later to see if more broke loose.
if it bad in there it takes a while for it all to come loose.
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Re: Rear heat operation

Postby redfury » October 21st 2011, 3:43am

My van didn't have the rear heater valving, which I bought off another member here as he parted out his van...the lines were clogged with what almost looked like a brown flossy material. I cleaned them out and I have wonderfully hot heat in the back...so hot my son complained that it was burning his foot. You've got a problem with flow and you'll want to do as prescribed above. The other thing to do is make sure that the valve is opening for the rear heat properly...

You can do that by bypassing the electric switch and run straight vacuum to the lower vacuum port on the switch. It's located beneath the alternator on the heater box. It's kind of difficult to see or get at, but if you look, you'll see a small electrical connector going into a small component with a vacuum line going down to the valve that opens the rear heat. Route direct vacuum to the valve and it'll keep it open whenever the engine is on so that you can get that junk flushed out of there.

You may have to reverse flush the system to get the crud loosened up. If you can manage to get that done, it'll be the best instead of trying to loosen the rear heater lines and flush them manually, it sounds like your whole system needs a good clean out.
A temporary fix usually becomes a permanent solution, therefore it does not exist.
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Re: Rear heat operation

Postby Lumpy » December 18th 2011, 4:57am

espionage33 wrote:
... My plan is to use a garden hose to flush out the system until the water is clear again, i think it may be clogged up quite a bit..



I flush mine in exactly that manner. Put some cleaner in there, as Maher suggests, for a few days. Then
start sticking the garden hose in every open end of every hose and fitting. Go easy on the high pressure
hose when you're shooting into the radiator and heater core(s) (front and rear). I just let the low pressure
water flow for several minutes till it comes out clear on the other side. Then reverse. Then reverse again.

Replace the thermostat while you're in there. It's six dollars.

While you've got hoses off, inspect them and replace if you feel the need.
The 3/4" ID hose is a dollar per foot. Simple to replace that. The upper and
lower big diam hoses are more costly but you won't be doing that again for
several years.

Button it all up. Fill with 50/50 GREEN or YELLOW cool juice or DexCool depending
on your religion. Burp it a few times over the next several miles.

Repeat next year.


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