Rear Heater question

[wilson234]

Switch works, fan blows low or high depending on the switches on dash, problem the air is not hot, not even warm just cold or outside temp. Front heater works fine, what could cause this? I’m assuming the front and rear heaters share the same heater core? If not where is the heater core for the rear heater?

 

[Mark W]

Nope. The heater core for the rear heater is... in the rear heater.

Mark...

 

[Rusty Marlin]

It's under the front passenger seat.
Has it's plumbing been bypassed by a PO?

 

[wilson234]

I will check under the passenger seat, now that I know if it’s location. Could have been bypassed by prior owner as I’m not original owner. I’m assuming the bypass would be noticeable either at the heater core under the passenger seat or in the engine compartment near the firewall? Curious is the rear heater core a common failure point, hence why someone would bypass?

 

[SpenserAK]

Rear heater bypass can be seen at the firewall, yes. In a 1FZ, you'll see it next to the heater control valve and valve cover on passenger side.

People bypass the rear heater because it simplifies the cooling system by eliminating a bunch of connections and a few small pipes, and it's easy/cheap - and sometimes parts of the rear hard lines are in bad shape, so they can be a failure point. Some are not exactly easy to replace with the engine in. In my case it was the smaller sections under the truck that were very crusty. I never need the rear heater, so it was a very easy way to deal with it. I've eliminated failure points for now & can choose to replace things at my leisure, if I ever want the rear heater.

 

[Fj80oregon]

Post a picture of your engine bay where your heater valve is on the firewall so we can see the whole fire wall and can look at the piping. Easy to see if it’s routed differently than normal.

 

[Mark W]

I will check under the passenger seat, now that I know if it’s location. Could have been bypassed by prior owner as I’m not original owner. I’m assuming the bypass would be noticeable either at the heater core under the passenger seat or in the engine compartment near the firewall? Curious is the rear heater core a common failure point, hence why someone would bypass?

I have seen numerous mentions here on mud about the rear heater being a problem point that people might chose to eliminate.
Currently I have 4 80 series rigs in "daily driver" status. Over the years I have owned another 5 IIRC. I'd guess that in the 20 or so years I have been driving them, I have racked up about 400,000 miles in the drivers seat of the various '80s. I have a dozen parts rigs in the yard, most of which I have knowledge of their condition as "runners" before they wound up as"parts".

I don't really keep track of how many '80s I work on routinely, much less the "once or twice" ones.

Around here, heaters matter. And rear heaters add a lot to the comfort of the rig when you are bopping down the highway at -20 or colder.

My point? I have yet to encounter a rear heater that is a leakage problem.

Not saying that it does not happen. Only that based on my experience it is an uncommon thing. From conversations I have heard/read it seems that more than a few of those who have bypassed their rear heater have done so preemptively. Seems silly yo me, but...

In any case, it is probably more likely that your's has in fact been bypassed than it is that it is simply clogged to the point of not passing heat.

Mark...

 

[NeverFinis]

It isn't the rear heater core that is the problem, but the lines going to the rear heater. In the rust belt US States, those metal lines rust out really fast. Most don't know those metal lines are there until they start losing coolant. One needs to remove the engine to replace the upper metal line, so it is easier to bypass.

Mine did rust through, and I did bypass it for a long time. I now have replacement lines installed since I pulled the engine for a swap.

 

[tmxmotorsports]

The rear heater lines are still available from Mr T

 

[Broski]

I have seen numerous mentions here on mud about the rear heater being a problem point that people might chose to eliminate.
Currently I have 4 80 series rigs in "daily driver" status. Over the years I have owned another 5 IIRC. I'd guess that in the 20 or so years I have been driving them, I have racked up about 400,000 miles in the drivers seat of the various '80s. I have a dozen parts rigs in the yard, most of which I have knowledge of their condition as "runners" before they wound up as"parts".

I don't really keep track of how many '80s I work on routinely, much less the "once or twice" ones.

Around here, heaters matter. And rear heaters add a lot to the comfort of the rig when you are bopping down the highway at -20 or colder.

My point? I have yet to encounter a rear heater that is a leakage problem.

Not saying that it does not happen. Only that based on my experience it is an uncommon thing. From conversations I have heard/read it seems that more than a few of those who have bypassed their rear heater have done so preemptively. Seems silly yo me, but...

In any case, it is probably more likely that your's has in fact been bypassed than it is that it is simply clogged to the point of not passing heat.

Mark...

Just depends on where you live, If you live where the average temperature is 65° year around ( Me ) then there’s no need for a rear heater.
I removed mine and it was working fine. It didn’t seem silly to me.

I have a perfectly good rear heater core if anyone needs one