Hey guys...been a while since my last post. The good-ol' '93 4.0L E4WD Aero* ext'd has been running pretty good, but, with the cold weather, I've noticed I'm not getting very much heat out of the heater/defroster, takes a long time to warm-up, and the gauge never reads over the "N" (usually runs below "N"). I've replaced the thermostat and checked that the coolant was full. No changes.

Any thoughts of where to check next?

TIA!

 

To give yourself a good indication of the exact temp, grab the upper radiator hose after it comes up to operating temp. How hot is it?
I've replaced three in the last year on my '93 4.0 extended. I've only had good luck with a genuine Ford replacement. Stay away from the cheap replacements. What brand did you use?

 

check the temps of both heater hoses going into the firewall. one should be the temp of the top radiator hose and the other only slightly cooler.

either a plugged heater core or a stuck blend door in the heater assembly
how are the vacuum hoses going to the heater control?

pull the rubber dam at the top of the radiator, creates a hole to put a section of waterproof cardboard down. block half the core. heats faster.

the heat gauge on these Aeros is not accurate. most run toward the bottom of the scale. only reliable way is a thermo. in the radiator hole.

 

Two separate problems. First is either heater core or blend door as noted above.

The dash gauge is off because the sender unit is bad. There are two sender units, one for the computer (2-lead affair) and a single lead sender located close by the thermostat housing for the dash gauge. If you replace that, you will likely find the guage reads between the "O" and "R" on NORMAL.

 

Also make sure the heater core is not blocked (one hose will be cold). With sub zero temps here in the GWN mine takes about 15 mins to get decent heat. It does get there ....just takes longer than in normal weather.

 

one other possibility is the heater shutoff valve in the heater hose line just prior to the hose going into the firewall entrance to core. failed valve, also constricted and plugs easily.
not all years have them.

 

the fact that there were no changes after replacing the t-stat tells me you have a bad gauge sender. I had a bad sender and went through several aftermarket t-stats. I replaced the sender with a genuine ford one, and also put in a Ford t-stat. Only the OE stuff worked.

I second that you could have a heater core issue. This is especially likely if the coolant is not replaced regularly, if a tap water coolant mix has been used, if any type of stop leak product has been used, or if rust colored sludge has built up in the cooling system.

 

Have you checked the clutch fan?