I'm going to repost this again and use different wording, I guess people didn't understand me before. I have a 1999 Ford E150 Conversion Van. With front and rear Heat and A/C. Front and rear are control from the dash switches only. Both the rear and front blower do not run on low. Runs on level 2,3 and 4. But level 4 (high) seems to be level 3. I replace the front blower motor and the resistor in the front. Some people say it's the swithches. But the Switches are seperate, is it possible they are wired some way together? Before I tear apart the dash I wanted some opionions.

Bob
1999 E150 Conervsion
2012 BMW K1600GTL
2014 Honda CTX700D

 

Show a photo of your dash blower motor speed switch---that might help explain some things here.

OR the lazy way is answering whether your van has controls in the rear area headliner for control of the rear blower?

 

all controls are on the dash, no control in back at all. On the dash, the temp dials controls both front and back, so the the vent location. Two blowers switches. Top one in for the front 4 position with 4 speeds. Bottom swithch has 5 position. Fist is off, then four speed position. But both have no power going to the bloswer in first or low postion. That is the best I can explanin it. Replace all there is to replace. At at a waste of money.

 

The low speed positions are the most likely ones to run into problems because in those positions there is a large resistor in the circuit that supplies an additional load so that the voltage drop across the motor is less (and it turns slower). So you have high current flowing in the low speed positions and it tends to burn up switches, connectors and resistor blocks.

So I'd say that it's simply coincidental that both your front and rear blowers have lost the low speeds. They don't share any common circuitry as far as I know. Examine the connector to the resistors both front and rear. If they look at all burnt or corroded, replace them. "Pigtail" connectors are available just for this purpose. When you have them unplugged, you can check that you have voltage between ground and at least one pin of the resistor connectors in each fan speed position except off. If you don't, it's most likely the switch but could be wiring along the way. Usually when switches go bad, they loose the nice snap between settings and you'll see some signs of burning on the backside of them. Do not bother replacing motors, this is not the problem. You've replaced one resistor block it sounds like, but another poster here found that one he purchased was bad from the factory. Tough to spot, but you can check them with an ohm meter. Here's a how-to that looks pretty good: http://troubleshootmyvehicle.com/for...esistor-test-1

Hope this helps...

 

Oh, one other thought. You mention it is a conversion van. Sometimes conversion companies do some funky stuff with the rear HVAC systems and it's possible that they altered the wiring so that you only have three speeds. If they installed an aftermarket rear unit, it may have come with a different resistor block that only has three speeds, but they did not want to bother changing the switch down to a three position switch.

 

Interesting, it is an aftermarket non OEM rear system. But would that affect the front blower fan as well. BTW, I replaced both blower switches on the dash and the relay in the engine compartment. Same, only three speeds for front and rear. Bob

 

If you can find the make/model of the rear unit you should be able to find out if it only has three speeds. I'm quite suspicious that this is what is causing your issue with the rear.

Front should have four speeds, however I think one of the aftermarket resistor blocks I got took a short cut and had the middle two speeds the same. Another poster mentioned finding a bad resistor block from the factory, so that could happen. The link I posted before shows how to test it. From that same website, here's the link to test the switch: Part 1 -How to Test the Blower Control Switch (Ford 4.9L, 5.0L, 5.8L)

If you run the tests way down on the actual resistor connector then you also check the wiring between the switch and the connector of course.

I think that's about it. If you still can't get the fourth speed after doing the above recommendations, You've got something very bizarre going on. The relay would not cause the problem in the front. I have seen rear relays on aftermarket units where there was a separate relay for each speed and so that could cause a loss of individual speeds.