I have a fan that only works on three quarter speed, if I advance the dial to highest fan speed it cuts out. I changed the blower module? under the hood but still the same issue? Any ideas how to resolve this I would love to get more air conditioning blowing

 

What are you working on?

 

For many models there is a high speed blower relay which kicks in just for the high speed. The relay could be the issue.

 

Sorry I should have known to put that info. 2000 B3500 Dodge Van 360 engine.

 

Thank you that is good info I will check for a relay issue.

 

I found the 50 amp relay and switched it out with another 50 amp relay from battery 1 but it did not help and looks ok, although i could try a new one later?

 

Looks like there are two relays for the blower motor, one feeds power for the lower speeds, the second one is for high. Have you check the blower motor resistor block?

 

Yes I changed out the old resistor block for a new on and changed the relay, no luck. I have found out the ac was not working and someone cut out and bypassed the high limit resistor to get it running again. Not sure if that has anything to do with it, or if that will cause other issues.

 

Could also be a bad speed selector switch.

 

Thanks that's what I will try next